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September 16-19, 2025 • Boulder, Colorado

Tuesday, September 16

Short Course, 9:00 – 2:15 PM

Room: SEEC S228

9:00 – 10:00
Amelia Davenport (Arkema) – Intro to Fundamentals of UV Curing
10:10 – 11:25
Chris Bowman (University of Colorado) – Photopolymerization Kinetics
12:00 – 1:00
Mike Idacavage (Radical Curing) – Applications of UV Curing
1:10 – 2:10
Allan Guymon (University of Iowa) – Design of Experiments

Plenary Sessions, 2:30 – 5:30 PM

Room: SEEC C120

2:30 – 3:00

Photoresponsive and adaptable hydrogels for biological applications

Kristi Anseth, University of Colorado Boulder

3:00 – 3:30

Novel Photopolymerization of Lipoic Acid Derivatives

Craig Hawker, UC Santa Barbara

3:30 – 4:00

Singlet-singlet resonance energy transfer: a valuable mechanism to speed up the photoreactivity in photopolymerization processes

Xavier Allonas, Universite de Haute Alsace

4:00 – 4:15

Break

4:15 – 4:45

Better Together: Photoredox & Copper Dual Catalysis ATRP

Krzysztof Matyjaszewski, Carnegie Mellon University

4:45 – 5:15

Crystallinity in polymer networks for differentiation of mechanical and optical properties in multi-material printing

Katharina Ehrmann, Technische Universität Wien

Wednesday, September 17

Plenary Sessions, 8:30 – 9:30 AM

Room: SEEC C120

8:30 - 9:00

Irresistible Force vs. Immovable Object: The Challenge of Commercializing New Materials in a Restrictive Regulatory Environment
Michael Gould, Rahn Corp

9:00 - 9:30

Microenvironments as an Explanation for the Mismatch between Photochemical Absorptivity and Reactivity
Christopher Barner-Kowollik, Queensland University of Technology (QUT)

9:30 - 9:45

Break

Parallel Sessions, 9:45 AM – 12:15 PM

TRACK 1 (Rm: SEEC C120)
TRACK 2 (Rm: SEEC S372 A/B)

9:45 - 10:10

Photopolymerisation and controlled depolymerisation of ketone-containing polymers
Andrew Dove, University of Birmingham
Towards high-speed additive manufacturing of nano-resolution polymeric materials - hierarchical structure control via wavelengths and molecular assembly
Kaiwen Hsiao, Texas A&M University

10:10 - 10:30

Mechanistic insights on the photopolymerization of 1,2-dithiolanes utilizing photo NMR
Benjamin Nelson, University of Colorado Boulder
Urethane-Urea Acrylate Resins for 3D printing
Jin Lu, Allnex Inc.

10:30 - 10:55

Green synthesis of photo-clickable polymers for efficient hydrogel crosslinking and programmable degradation
Chien-Chi Lin, Purdue University
Development of 3D Printing Resins with Tunable Properties from Glycerol-Derived Monomers and Waste Plastics
Jason Bara, The University of Alabama

10:50 - 11:10

Break
Break

11:10 - 11:35

4D Grayscale Modulation of Living Systems
Cole DeForest, University of Washington
Speaking in Dp and Ec – Expanding the Working Curve to Standardization, High Resolution, and Mechanical Precision
Jason Killgore, National Institute of Standards and Technology

11:35 - 11:55

Photoresponsive Synthetic ECM to Model Lung Microinjury and Fibrosis-Associated Secretome
Samantha Swedzinski, University of Delaware
Material Development with Focus on Mechanical Performance for Vat Photopolymerization
Ye Wang, TE Connectivity

11:55 - 12:20

UV Curable Dielectric Materials
Don Herr, Arkema
Radical-free 3D printing via photoclick chemistry
Javier Read de Alaniz, UC Santa Barbara

Lunch, 12:20 – 1:45 PM

Parallel Sessions, 1:45 – 3:35 PM

TRACK 1 (Rm: SEEC C120)
TRACK 2 (Rm: SEEC S372 A/B)

1:45 - 2:10

In Situ NMR to Monitor Bulk Photopolymerization Kinetics
Allan Guymon, Brigham Young University
Increase of spatio-temporal resolution of 3D printed objects via controlled polymerization of acrylates or epoxides
Céline Croutxé-Barghorn, Université de Haute Alsace

2:10 - 2:30

UV-Curable Resins and Their Composites for Applications Ranging from the Micrometer to the Meter Scale
Christian Dreyer, Technical University of Applied Sciences Wildau & Fraunhofer IAP Wildau
A Formulator's Guide to Catalytic Chain Transfer in Thermosetting Photopolymers
Brian Donovan, University of Denver

2:30 - 2:50

Design and 3D printing of biobased epoxidized formulations based on vegetable oils with vitrimeric properties
Matilde Porcarello, Politecnico di Torino
Development of Parallax Volumetric Additive Manufacturing for Rapid, Large-Area 3D Fabrication
Chi Chung Li, University of Colorado Boulder

2:50 - 3:10

Photochemistry to the rescue- our 8 year journey to develop a melamine primer
Tommy Haraldsson, Mercene Labs AB
UV Curable Ultra Low Refractive Index Nano-voided Materials
Eric Nelson, 3M

3:10 - 4:00

Break
Break

Poster Session A and Vendor Exhibit, 4:00 – 6:00 PM

Thursday, September 18

Plenary Sessions, 8:30 – 10:00 AM

Room: SEEC C120

8:30 - 9:00

Regulating polymer properties through combined covalent and physical network structure
Jeff Stansbury, University of Colorado

9:00 - 9:30

Photomediated Synthesis of Ultra-High Molecular Weight Polymers for Advanced and Programmable Circular Materials
Brent Sumerlin, University of Florida

9:30 - 10:00

Photopolymer Challenges for Volumetric Additive Manufacturing
Robert McLeod, University of Colorado Boulder

10:00 - 10:15

Break

Parallel Sessions, 10:15 – 12:15 PM

TRACK 1 (Rm: SEEC C120)
TRACK 2 (Rm: SEEC S372 A/B)

10:15 - 10:40

Spatial Control of Thiol-Ene Curing Kinetics by Antagonistic Photoreactions
Thomas Griesser, University of Leoben
Switching between Cationic and Radical Polymerizations
Brett Fors, Cornell University

10:40 - 11:00

Thiol-based coatings enhance the optical properties of elastomers fabricated with VAT photopolymerization for medical applications
Alan Aguirre-Soto, Tecnologico de Monterrey
Digital Light Processing of Bio-Derived Conductive Composites with Joule-Heating Capabilities
Alberto Cellai, Politecnico di Torino

11:00 - 11:15

Break
Break

11:15 - 11:40

Sub-optical stress field analysis in heterogeneous polymer films
Lewis Cox, Montana State University
Sustainable UV-Cured polymer: from coatings to composites and additive manufacturing
Marco Sangermano, Politecnico di Torino

11:40 - 12:00

Kinetic modeling of diffusion-limited thiol-ene photopolymerization
Yunfeng Hu, University of Colorado Boulder
Understanding reactive conversion of polymers for additive manufacturing of functional materials
Max Saccone, University of Colorado Boulder

12:00 - 12:45

Constructing and Deconstructing Thermosets with Light and Thiols: Polarity Reversal Catalysis and Dual-Trigger Strategies
Derek Patton, University of Southern Mississippi
Kinetics-Driven Design of Next-Generation 3D Printing Materials
Sijia Huang, University of Utah

Lunch, 12:20 – 1:45 PM

Parallel Sessions, 1:45 – 3:35 PM

TRACK 1 (Rm: SEEC C120)
TRACK 2 (Rm: SEEC S372 A/B)

1:45 - 2:10

Shape-morphing particles from photocrosslinkable copolymer films
Ryan Hayward, University of Colorado
Aqueous PhotoATRP of Responsive Polymers from Structured Peptide Assemblies
Christopher Kloxin, University of Delaware

2:10 - 2:30

3D printable, mechanically robust, nanostructured block copolymer hydrogels
Arkodip Mandal, University of Colorado Boulder
Dual Cure Approaches to Polymer Networks Involving Dynamic Chemistry
Alexander Osterbaan, University of Colorado Boulder

2:30 - 2:50

3D Printing of PolyHIPE Scaffolds with Bioactive Glasses: a Bio-Based Platform for Bone Tissue Regeneration
Matteo Bergoglio, Politecnico di Torino
Production of Rare Earth Elements Using 3D Printed Ion Exchange Resins
Sophie Morton, University of Utah

2:50 - 3:10

High-Performance 3D-Printing Resins Based on Triazine Cores and Isocyanate-Free Urethane–Acid Networks
Sean Keyser, University of Colorado
Surface-Initiated Photopolymerization: Exploring the Power of Germanium Photoinitiators
Christine Bandl, Technical University of Leoben

3:10 - 3:35

Hierarchically structured, functional coatings from photo-based processes
Caroline Szczepanski, Michigan State University
Photo + ROMP: Using light in unique ways to control ring-opening metathesis polymerizations
Leah Appelhans, Sandia National Laboratories

3:35 - 4:00

Break
Break

Poster Session B and Vendor Exhibit, 4:00 – 6:00 PM

Friday, September 19

Parallel Sessions, 8:30 – 10:00 AM

TRACK 1 (Rm: SEEC C120)
TRACK 2 (Rm: SEEC S372 A/B)

8:30 - 8:55

Molecularly engineered, light-responsive building blocks for the creation of well-defined bioinspired cellular microenvironments
April Kloxin, University of Delaware
Photopolymerization of Liquid Crystalline Phases for Structurally Programmed Optical Materials
Timothy White, University of Colorado Boulder

8:55 - 9:20

TBD
Stephanie Bryant, University of Colorado Boulder
Development of polyamide in photo-curable materials
Chen Wang, University of Utah

9:20 - 9:40

Kinetic Control of Photochemical Reactions Enables the Fabrication of Reprogrammable Gels
Manuela Garay-Sarmiento, University of Colorado Boulder, BioFrontiers
Effect of Functional Groups on Acrylate Photopolymerization Kinetics during UV Cure
Robin Crownover, US Army DEVCOM AC

9:40 - 10:00

Break
Break

Plenary Sessions, 10:00 AM – 12:30 PM

10:00 - 10:30

Type III Photopolymerization as a new Paradigm for Light-Based 3D Printing
Zachariah Page, The University of Texas at Austin

10:30 - 11:00

Arts and crafts by photopolymerization: programming complex actuation in liquid crystalline elastomers
Tayler Hebner, Purdue University

11:00 - 11:30

Design and Properties of Controlled Liquid Crystal Elastomer Networks
Emily Davidson, Princeton University

11:30 - 12:00

Photo-responsive Dynamic Networks
Stuart Rowan, University of Chicago

12:00 - 12:30

Dithiolane (Co)polymers and Their Potential Applications
Christopher Bowman, University of Colorado Boulder

Lunch, 12:30 – 1:30 PM

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Photoresponsive and adaptable hydrogels for biological applications

Kristi Anseth, University of Colorado Boulder

This talk will illustrate several examples of the development and application of poly(ethylene glycol) (PEG) hydrogels with photo-adaptable and/or responsive crosslinkers, especially those that impart unique material properties for biological applications. One example will illustrate the formation of hydrogels from bottlebrush polymers and how strain-stiffening mechanics facilitates the formation of protrusion-rich osteogenic cell populations, similar to osteocyte networks found in bone. In another vignette, dithiolanes are investigated as PEG crosslinkers, producing biomaterials capable of multiple light-driven mechanical transformations including stiffening, softening, and photo-induced stress relaxation. This same chemistry is further exploited to provide controllable elasticity in highly dynamic dual-crosslinked hydrogels that also contain boronate ester bonds. These matrices are compatible with light-based biofabrication techniques, allowing for spatiotemporally templated encapsulation of cells that rapidly self-organize and colonize the synthetic microenvironment as a function of viscoelasticity. Finally, photoadaptable, allyl sulfide functionalized PEG hydrogels allow for the growth of intestinal organoids, and the subsequent application of photopatterned light to locally alter epithelial curvature, initiating symmetry breaking events, and ultimately directing cell fate.

Novel Photopolymerization of Lipoic Acid Derivatives

Craig Hawker, UC Santa Barbara

The radical ring-opening polymerization (rROP) of α-lipoic acid (LA) and its derivatives represents a synthetically accessible, efficient, and scalable strategy to impart degradability into functional copolymers. By combining with traditional photopolymerization techniques, the design of sustainable materials containing LA through rROP driven by light can be achieved. This allows for a wide variety of new approaches to be contemplated. For example, the development of renewable vinyl-based photopolymer resins offers a promising solution to reducing the environmental impact associated with 3D printed materials. Lipoate monomers and cross-linkers containing dynamic disulfide bonds can be combined with acrylic monomers (n-butyl acrylate) and conventional photoinitiators to develop photopolymer resins that are compatible with commercial stereolithography 3D printing. The incorporation of disulfide bonds within the polymer network’s backbone imparts the 3D printed objects with self-healing capabilities and complete degradability. In addition, this facile synthetic approach provides access to dithiols which creates opportunities for upcycling of degraded materials and the ability to prepare multiblock copolymers using a synthetically simple and versatile photopolymerization platform.

Singlet-singlet resonance energy transfer: a valuable mechanism to speed up the photoreactivity in photopolymerization processes

Xavier Allonas, Université de Haute Alsace

Photopolymerization reactions have been continuously evolving for over 60 years. Today, new horizons have emerged, particularly in vat photopolymerization-based 3D printing. This highly specialized field has led to numerous publications in recent years and is considered one as of the most promising for the future. However, it must be acknowledged that radical photopolymerization, despite its widespread use, is currently reaching a plateau: increasing the efficiency of photoinitiators in the UV or visible range remains a significant challenge. In this paper, we will describe an original way to improve the reactivity of Type I photoinitiators. Recently, we have found an intriguing photosensitization process based on singlet-singlet resonance energy transfer from a fluorescent dye to phosphine oxide photoinitiators [1-2]. This effect allows a remarkable increase in reactivity, with sensitization ratio higher than 4. The underlying photochemistry is deeply described, taking into account the spectral overlap between the emission spectrum og the photosensitizer and the absorption spectrum of the photoinitiator.

Better Together: Photoredox & Copper Dual Catalysis ATRP

Krzysztof Matyjaszewski, Carnegie Mellon University

Photomediated Atom Transfer Radical Polymerization (photoATRP) is an activator regeneration method that enables the controlled synthesis of well-defined polymers through light irradiation. Traditional photoATRP is often limited by the need for high-energy ultraviolet or violet light. These could negatively affect the control and selectivity of the polymerization, promote side reactions, and may not be applicable to biologically relevant systems. This drawback can be circumvented by introducing a catalytic amount of photocatalysts, which absorb visible and/or NIR light. Therefore, controlled, regenerative ATRP can be performed with the dual-catalytic cycle. Recent developments in the field of dual-catalysis concerning Cu-catalyzed ATRP at ppm level and photocatalysts down to ppb level will be discussed. Well-defined polymers are prepared at rates dependent on the amount and quantum efficiency of PC, and their controlled polymer architecture is defined by the Cu-catalysts. Thus, Cu catalysts and photocatalysts can act much better together, providing robustness, oxygen tolerance, and access to new materials.

Crystallinity in polymer networks for differentiation of mechanical and optical properties in multi-material printing

Katharina Ehrmann, Technische Universität Wien

Long-range order, i.e. crystallinity, in polymer networks is difficult to achieve, in particular for fast polymerization mechanisms suitable for stereolithography or DLP printing. While post-polymerization crystallization is suitable for elastic networks, the issue becomes even more pronounced for rigid polymer networks with a rather high crosslinking density, lowering achievable degrees of crystallinity. We demonstrate the “trapping” of crystallinity via photopolymerization from the liquid crystalline state of a thiol-ene formulation at temperatures of 80-110 °C, enabling us to produce bulk and DLP printed crystalline specimens with melting enthalpies up to 25 J g-1 (estimated to be about 37% crystalline), in combination with high initial strain responses of 10-20 MPa (before yielding). In a second step, we tuned the curing conditions via printing temperature and irradiation intensity such that 3D printing at 80 °C yielded opaque, stiff semi-crystalline materials and printing at 110 °C yielded transparent, elastic amorphous materials from the same formulation. We further demonstrate data storage and shape memory applications for these multi-material structures.

Irresistible Force vs. Immovable Object: The Challenge of Commercializing New Materials in a Restrictive Regulatory Environment

Michael Gould, Rahn Corp

With a 40 year history of creating new molecules, the author will reflect on the ever-more restrictive global regulatory landscape (immovable object) at a time when new technologies demand new, better, safer and more sustainable chemical building blocks (irresistible force).Photopolymer 3D printing, as an example, is a demanding application that begs greater performance from materials historically created for other industrial applications. During the past 10 years, the need for new high performance photopolymer materials has grown dramatically as printer and process capabilities evolve in rapid generational leaps. At the very same time, global legislators have ‘seized the moment’ and created a historically challenging gauntlet of rules and regulations that obstruct innovation and ‘tax’ commercial endeavors to a point where innovation is prohibitively expensive. Feedback to elected officials is the only sure way to move the needle back to a more common sense perspective. Until we reach that place, patience and determination are necessary to maintain creative momentum in a positive direction.

Microenvironments as an Explanation for the Mismatch between Photochemical Absorptivity and Reactivity

Christopher Barner-Kowollik, Queensland University of Technology (QUT)

When selecting a light source for a photochemical process — including for photopolymerizations — we often consider the likelihood of a photon to be absorbed by a chromophore at a given wavelength as an accurate predictor of how well a photo-chemical process will proceed when irradiated with different colors of light. Over the last decade this paradigm has been repeatedly challenged for many photochemical systems, as a distinct mismatch between the absorption spectrum and the wavelength resolved photochemical reactivity has been observed. Herein, we unravel underlying mechanisms behind the mismatched reactivity and absorbance in photocycloadditions. Initially, we probe the impact that an equilibrium established between reversible photochemical processes has on the mismatch for a pyrene-chalcone molecule. Subsequently, we establish a critical link between photophysics and photochemistry with a theory based on the selective excitation of specific microenvironments leading to molecular transitions that allow for favourable wavelength-dependent reactivity. Time-resolved and steady-state fluorescence spectroscopy measurements confirm the presence of this selectivity, with both displaying significant red-edge effects that are observed in fluorescence spectroscopy literature, further supporting our theory. By synthetically tethering chromophores together, we further evidence the importance of microenvironments and their wavelength-dependent excited-state lifetimes, presenting the missing link that explains the mismatch for many photochemical systems. The implications of the theory presented herein stretch from additive manufacturing to photo-dynamic therapy, meaning that we can potentially leverage photochemical mismatches by changing the properties of the environment surrounding the chromophore. Carrol, J. A.; Pashley-Johnson, F.; Klein, M.; Stephan, T.; Pandey, A. K.; Walter, M.; Unterreiner, A. N.; Barner-Kowollik, C. J. Am. Chem. Soc. 2025, in press.

Photopolymerisation and controlled depolymerisation of ketone-containing polymers

Andrew Dove, University of Birmingham

While many routes exist to mediate photopolymerisation of a range of monomers, the reverse process, depolymerisation is much less studied. While photodegradation of polyketones, typically accessed by copolymerisation of CO with alkenes, is well established to occur by Norrish photodegradation pathways, it results in an uncontrolled photodegradation to a mixture of products. Herein, we will present the photomediated synthesis of poly(enone sulfide)s and discuss their selective photo-depolymerisation.

Towards high-speed additive manufacturing of nano-resolution polymeric materials – hierarchical structure control via wavelengths and molecular assembly

Kaiwen Hsiao, Texas A&M University

Polymeric materials containing hierarchical structures ranging from micrometer to nanometer feature sizes play a significant role in accelerating transport properties, critical for energy-water and biomedical applications. Major advances in high-speed, high-resolution additive manufacturing (AM) have demonstrated the capability of creating architected materials at the micrometer resolution. However, challenges existed in achieving sub < 500nm nanostructure control due to the limitation in projection optics and writing speed, as well as limited understanding of preservation and evolution of nano-morphologies during photo-patterning. In this research, we aim to address this challenge with two approaches. In the first part of the talk, we will focus on the introduction of dual-wavelength 3D printing platform coupled with controlled living radical polymerization to tackle the diffraction-limited patterning. The critical timescales of reaction-diffusion mechanism are elucidated with experiment and simulation. It was found that at the diffusion-limited printing time, the patterning resolution is dictated by the diffusivity and lifetime of the macroradicals. To achieve sub-500nm resolution, macroradical reactivity and projection optics exposure time needs to be simultaneously controlled to enter reaction-limited regime. In the second part of the talk, we will focus on a bottom-up approach using macromolecular-amphiphilic templates for controlling self-assembly nano-morphologies formation during rapid photo-crosslinking in AM platforms. The nano-morphologies preservation before and after printing are elucidated with SAXS, SEM, and DSC. It was found that without effective functionalized amphiphilic templates, the onset of polymerization driven microphase separation occur due to the thermodynamic depletion effect, leading to nano-morphologies coarsening of the bi-continuous micellar domains. Functionalized amphiphilic macromolecules are introduced to control the evolution of nanostructure formation. Taken together, the research builds on fundamental reaction-diffusion control with two different approaches to achieve sub-500 nm resolution within scalable AM platform, and provides a fundamental understanding towards the enhancement of patterning resolution with low-energy laser systems.

Mechanistic insights on the photopolymerization of 1,2-dithiolanes utilizing photo NMR

Benjamin Nelson, University of Colorado Boulder

The rapid development of 1,2-dithiolanes for material applications continues to be reported by several groups. A key feature of dithiolanes useful in materials science is their ability to undergo polymerization via a variety of mechanisms, including thermal, anionic, cationic, radical, and initiator-free photopolymerization. This inherent capability of photopolymerization has been a central driving force in the materials development utilizing dithiolanes. However, the long-standing hypothesis of a radical mediated polymerization mechanism has fallen under scrutiny given both recent and older developments reported in the literature. Namely, the requirement for exogenous photoinitiator in the copolymerizations of dithiolanes and various alkenes, as well as the pronounced solvent effect on the polymer structure and distribution casts doubt on a radical mechanism. In this study, the unconventional technique of photo NMR was used to track the kinetics of the initiator free dithiolane photopolymerization, using lipoic acid as a model dithiolane, revealing mechanistic insights about the polymerization. Through time resolved spectroscopy during light irradiation, a reactive intermediate was tracked and identified. This mechanistic understanding of the polymerization mechanism furthermore enabled the use of lipoic acid as a cationic photoiniator to polymerize vinyl ethers.

Urethane-Urea Acrylate Resins for 3D printing

Jin Lu, Allnex Inc.

3D printing by photo-polymerization has been successful in the dental market due to the efficiency of printing custom products in complex shapes in great detail. This printing process is also becoming increasingly accepted in the medical and industrial markets. Digital light processing (DLP) applies LED light to the whole surface of the resins in a single pass, offering faster printing speed than Stereolithography (SLA), thus gaining more popularity in the market. Many 3D printing applications require high thermoplastic-like performance but in a thermoset system. A lower viscosity is also needed to enable fast printing. To tackle these challenges, we designed and created a new type of urethane-urea acrylate oligomers, which can be formulated by high levels of monofunctional monomers without losing their strong mechanical performance. This photocurable resin system can be printed at a fast speed by a DLP printer and offers strong layer-to-layer adhesion and toughness.

Green synthesis of photo-clickable polymers for efficient hydrogel crosslinking and programmable degradation

Chien-Chi Lin, Purdue University

Orthogonally crosslinked thiol-norbornene hydrogels are a versatile biomaterial platform for tissue engineering applications. Multi-arm poly(ethylene glycol)-norbornene (PEGNB) is a popular synthetic macromer choice for thiol-norbornene hydrogel crosslinking, owing to its rapid reaction kinetics and high cytocompatibility. However, the synthesis of this photo-reactive polymer has been troublesome due to its tedious reaction conditions and the use of nauseous 5-norbornene-2-carboxylic acid. Furthermore, hydrogels crosslinked by conventional PEGNB do not provide highly tunable degradation, limiting their use in the tissue regeneration space. This talk will present carbic anhydride-based synthesis of PEGNB variants. The synthesis is greener, faster, and highly efficient, producing three new PEGNB variants: PEG-ester-norbornene-carboxylate (PEGeNBCA), PEGeNB-tyramide (PEGNB-T), and PEG-amide-NBCA (PEGaNBCA). These three PEGNB variants all have rapid thiol-norbornene photocrosslinking kinetics. Additionally, hydrogels photocrosslinked by these PEGNB variants afford highly tunable degradation, including slow hydrolytic degradation, fast dissolution, and user-controlled photodegradation. Autonomous hydrolytic degradation can be engineered over hours to months, whereas user-defined on-demand photodegradation can be achieved in minutes. The new family of photocrosslinkable PEGNBCA hydrogels is cytocompatible for in situ cell encapsulation and can be adapted for various biofabrication application workflows, including microgel fabrication, digital light processing (DLP) printing, and sacrificial bioprinting.

Development of 3D Printing Resins with Tunable Properties from Glycerol-Derived Monomers and Waste Plastics

Jason Bara, The University of Alabama

Development of sustainable and environmentally friendly stereolithography (SLA) 3D printing resins has gained considerable attention in recent years. Towards this goal, we have successfully employed glycerol-based 1,3-diether-2-methacrylate monomers that offer tunable mechanical and thermal properties based on selection of functional groups. These monomers also act as solvents for thermoplastics such as polystyrene (PS), poly(methyl-methacrylate) (PMMA), and poly(vinyl chloride) (PVC). This dual functionality enables the direct fabrication of polymer blends using a consumer-grade SLA 3D printer. This presentation will provide an overview of our synthetic methods, resin preparation, and the resulting structure-property relationships of the 3D printed materials.

4D Grayscale Modulation of Living Systems

Cole DeForest, University of Washington

Hydrogel biomaterials have proven indispensable for three-dimensional (3D) cell culture but have fallen short in replicating the innate physiochemical complexity of real tissue. Though traditional photolithography affords localized material manipulation, robust methods that govern when, where, and to what extent such phototailoring occurs throughout materials would be profoundly enabling towards fabricating more-realistic 3D tissue constructs. Here, we introduce “grayscale image z-stack-guided multiphoton optical-lithography” (GIZMO) as a generalizable and intuitive strategy to rapidly photomodulate materials in full 3D non-binary patterns at submicron resolutions spanning large volumes (>mm3). Highlighting its versatility, we employ GIZMO to variably photopattern stiffening/softening and biochemical (de)functionalization of cell-laden hydrogel biomaterials based on biologically derived or synthetic grayscale image stacks with unprecedented complexity. Additionally, combining GIZMO with next-generation optogenetic strategies, we demonstrate 4D grayscale activation bioactive proteins in functional materials and in living cells. We anticipate that GIZMO will enable new opportunities to probe and manipulate cell fates, as well as to engineer complex functional tissue.

Speaking in Dp and Ec – Expanding the Working Curve to Standardization, High Resolution, and Mechanical Precision

Jason Killgore, National Institute of Standards and Technology

The working curve describes the fundamental relationship between cure depth and radiant exposure in a photopolymer resin. Jacobs showed that a semi-log fit of the working curve yielded 2 parameters, the depth of light penetration Dp and the critical exposure energy Ec. Despite their implicit nature as material properties and ubiquity in vat photopolymerization literature, the precise measurement and demonstrated utility of Dp and Ec remain unresolved. For Dp and Ec to represent material properties, it is essential that the community adopt standards on how the measurement should be performed. Our results show that adoption of a common measurement method dramatically reduced the measurement variation from up to 7000 % for Ec and 700 % for Dp, down to ≈5 % or less for both quantities. Despite standardization providing a common basis for comparing resin properties, the values of Dp and Ec are still known to depend on numerous other factors such as irradiance of the light source and size of the printed features. To elucidate the impact of such process variables on Dp and Ec in bioprint relevant inks, we developed a novel instrument combining a high-resolution, high-power digital light processing projector and a high-speed optical coherence tomography imaging system. This instrument allows real time measurement of working curves on patterned features down to 10 µm in width, at irradiances up to 450 mW cm-2, through varying window materials. Working curves are seen to exhibit extreme size dependence, particularly at lower irradiances where the duration of cure allows considerable time for diffusion. Notably, by correcting for the size dependency of Dp and Ec ,one can determine exposure conditions that yield uniform cure depth across multiple pattern length scales. Finally, we consider how Dp and Ec affect the intralayer mechanical property gradients in printed parts. We introduce a new measurement of intralayer modulus coined the “wedge method” that employs a sloped removable backplate to measure the modulus at a given intralayer depth. By printing wedges at different irradiance and exposure, we observe a broad range of intralayer gradients. However, when the exposure is scaled by the irradiance-dependent Ec, the gradients collapse onto a master curve. Overall, consideration of Dp and Ec on a voxel-scale (with lateral and thickness dimensions) basis allows for parts to be manufactured with improved geometric and mechanical precision.

Photoresponsive Synthetic ECM to Model Lung Microinjury and Fibrosis-Associated Secretome

Samantha Swedzinski, University of Delaware

Microinjuries to the lung epithelial layer are hypothesized to trigger fibrotic cascades associated with lung diseases and cancer recurrence. A primary trait of these cascades are changes in the mechanical properties of the cellular microenvironment, including large increases in stiffness that correspond to decreases in lung function due to inhibited gas exchange. The early stages of these diseases are particularly not well understood due to the extended amount of time between disease initiation and onset of symptoms that lead to diagnosis. Therefore, we aim to create a synthetic hydrogel platform that mimics microinjuries and the subsequent increasing modulus of the ECM for probing cellular responses caused by these dynamic changes. Here, a bioinert poly(ethylene glycol) (PEG)-based hydrogel was formed using a coumarin-containing crosslinker to enable injury mimetic properties via selective photodegradation. The stiffening mimetic properties were then enabled by triggering thiol-yne reactions via visible light photoinitiation of Eosin Y. The biomechanical properties of this hydrogel-based synthetic ECM were modulated to mimic injury via selective photolithographic degradation and subsequent bulk photostiffening to mimic the injury-fibrosis cascade. Assessment of these mechanical properties was done by rheometry and confocal microscopy. Epithelial cells were cultured on these hydrogels at the air-liquid interface (ALI) and then subjected to injury, stiffening, or injury followed by stiffening and cellular responses assessed (cellular, proteomic, transcriptomic assays). The use of this photoresponsive hydrogel-based synthetic ECM platform enables insights into cellular responses to dynamic biomechanical changes associated with injury and fibrosis toward improved mechanistic understanding and therapeutic approaches.

Material Development with Focus on Mechanical Performance for Vat Photopolymerization

Ye Wang, TE Connectivity

Vat photopolymerization (VP), a major additive manufacturing process, has been widely adopted as manufacturing method for prototyping, tooling, and end-use parts. In the connector industry, development of VP machines, materials, and processes enables shorter design cycle and product time-to-market. However, the full potential of VP still needs to be explored, especially better understanding of VP material mechanical, physical, and other properties. In this work, a series of VP materials was prepared using base acrylate photopolymers with different additives to demonstrate recent development of materials with focus on mechanical properties. The addition of different liquid or solid additives to the base photopolymers can hugely impact material reaction under UV exposure, which further affects material response to external forces, material printability, part dimension accuracy, and product level performance. Through multiple case studies, we demonstrate the progress of VP materials development being explored for the connector industry.

UV Curable Dielectric Materials

Don Herr, Arkema

The need for high performance polymeric dielectric materials has been an area of commercial importance and R&D focus for several decades given the advancement of fields such as miniaturized and ruggedized electronics, flat panel and flexible displays, and battery component coatings. Unique and high throughput manufacturing processes for contemporary devices, including 3D printing, have created opportunities for reactive materials that extend beyond traditional insulator options such as epoxies, polyimides, silicones, and fluorocarbons. This talk will review 100% solids liquid light curable material options to create fairy high performance and cost effective dielectric devices, coatings and adhesives. Testing techniques and comparative data will be presented in relation to critical performance parameters such as such as bulk resistivity, breakdown strength, dissipation factor, and dielectric constant. The use of fillers in achieving targeted dielectric and other performance targets introduces resin/filler interface and light penetration challenges as with other filled UV curable materials. Key principles of structure/property design will be presented as guidance to the selection of base materials and the formulation of high performance light-cured products.

Radical-free 3D printing via photoclick chemistry

Javier Read de Alaniz, UC Santa Barbara

Photons have multiple enabling advantages to control chemical reactions, processes and 3D printed materials. In this seminar, I will discuss our groups effort to design and develop a radical- and additive free photo-resin system based on Diels–Alder click chemistry. Inspired by the high reactivity of cyclopentadiene (Cp), we employ photo-caged Cp derivatives that undergo efficient, light-triggered cycloaddition with maleimide groups. This design enables rapid gelation under mild conditions without metal catalysts or highly reactive radical initiators. The resulting hydrogels exhibit excellent photo-curability, as confirmed by photo-rheology studies, and support spatially controlled post-functionalization. Our system demonstrates full compatibility with DLP 3D printing, enabling the fabrication of complex hydrogel architectures with high resolution and minimal material waste. Furthermore, the modularity of our design offers pathways toward recyclability and degradability, essential for advancing circular material systems.

In Situ NMR to Monitor Bulk Photopolymerization Kinetics

Allan Guymon, Brigham Young University

Precisely measuring photopolymerization kinetics is critical in controlling curing characteristics and material properties in photocurable systems. Traditional methods used to measure kinetics, such as real-time Fourier-transform infrared spectroscopy (RT-IR), are often limited by broadening mechanisms intrinsic to the system, overlapping signals, and poor spectral resolution. This presentation will discuss an in situ NMR spectroscopy technique to monitor bulk photopolymerization reactions wherein the polymer system is separated from the locking solvent via a capillary insert and photoexcited using an LED-coupled fiber optic. This technique allows the isolated observation of the bulk reaction system while also benefiting from the high spectral resolution and rich chemical information offered by NMR. To optimize acquisition parameters, the relationship between nuclear relaxation and resin viscosity is investigated as a function of monomer conversion. The utility of this technique is shown by monitoring monomer conversion in photocurable hexyl acrylate and demonstrates exceptional reproducibility, minimal dark cure, and remarkable sensitivity to changes in reaction parameters such as light intensity and photoinitiator concentration. This technique is also applied to two challenges relevant to applications in photopolymerization, i.e. monitoring hydrogel polymerization kinetics and independent monitoring of acrylate/methacrylate monomer in a copolymerization reaction. By observing kinetic data of simple photopolymer systems, this work demonstrates the utility of in situ NMR photopolymerization as a complementary technique to conventional RT-IR and other methods for kinetic monitoring of bulk photopolymerization reactions.

Increase of spatio-temporal resolution of 3D printed objects via controlled polymerization of acrylates or epoxides

Céline Croutxé-Barghorn, Université de Haute Alsace

3D DLP printing of acrylate-based thermoplastics or epoxy-based thermosets was investigated by addition of RAFT-agents or pyridine derivatives, respectively. The impact of these compounds on the radical or cationic polymerization kinetics and the resolution of the 3D printed objects was explored. RAFT agents have an impact on the photopolymerization of acrylates, through the formation of more homogeneous 3D polymer network. Consequently, a significant improvement of the mechanical properties was noticed, with increased elongation at break values for samples exhibiting the same conversion. The toughness was also improved by about 20–25%. For epoxy-based resins, an increase of the inhibition time and a decrease of the heat flow were observed in the presence of pyridine derivatives and attributed to the trapping of the initiating species and the stabilization of the growing chains. This allows for the confinement of the polymerization process and limits the presence of lateral defects around the printed objects.

UV-Curable Resins and Their Composites for Applications Ranging from the Micrometer to the Meter Scale

Christian Dreyer, Technical University of Applied Sciences Wildau & Fraunhofer IAP Wildau

The presentation provides a comprehensive overview of the authors’ latest developments in the field of UV-crosslinking polymers, including a wide range of applications: Heat-resistant coatings which are cross-linked using modern energy-efficient UV LED modules for high-performance glass-fibers for the transmission of high (optical laser) power for use in laser surgery and material processing are described. Further applications in the micrometer range deal with photoresists, optical polymers and nanocomposites for optical waveguides for integrated optical components. The use of inorganic nanoparticles functionalized with organic groups leads to optically transparent waveguides with reduced thermo-optical coefficients (TOC). Furthermore, the development of adaptable materials for lenses and other applications in photonics is explained. Another project deals with the development of polymeric materials as well as process and tool development for UV-reactive injection molding. The use of UV-reactive resins for injection molded products promises higher fibre-volume contents (for example of short glass fiber reinforced components due to the significantly lower initial viscosity of reactive resins compared to thermoplastic melts) and thus higher achievable mechanical strengths as well as higher heat deflection temperatures – the last due to the network structure of the final components. Compared to the established purely thermal reactive injection molding, significantly shorter cycle times can be achieved with UV LED curing. One project that has already been successfully implemented in industrial practice involves the development of material and process for the hybrid (UV and heat) production of glass fiber-reinforced pultrudates as a continuous process. In addition to significant energy savings, an increase in speed of + 400 % was achieved.

A Formulator’s Guide to Catalytic Chain Transfer in Thermosetting Photopolymers

Brian Donovan, University of Denver

Methacrylate photopolymers are widely used in industries such as 3D printing and microelectronics due to their rapid curing under UV or visible light and ultimate performance characteristics. However, the chain-growth nature of their polymerizations often leads to brittleness, significant shrinkage stress, and limited mechanical properties. Conventional solutions involve custom-synthesized materials or complex multi-component formulations, as well as chain transfer agents (CTAs) that can be costly and require high loadings of specialized monomers (>20 wt. %). Herein, we present a sulfur-free catalytic CTA that can be added in ppm quantities to commercial monomer feedstocks, achieving similar results to traditional CTAs but at 10,000-fold lower loadings. Based on macrocyclic cobaloximes, these catalysts enable exceptional tunability in the (thermo)mechanical properties of methacrylate photopolymers while maintaining a complete cure. Significantly, modulus can be tuned as a function of light intensity and temperature, enabling the selective curing of a single composition into rigid, tough, or elastomeric forms, or the creation of high-fidelity, multi-modulus materials prepared via grayscaling techniques. Further, this technique is broadly applicable to high modulus (>1 GPa) and low modulus (<1 kPa) formulations.

Design and 3D printing of biobased epoxidized formulations based on vegetable oils with vitrimeric properties

Matilde Porcarello, Politecnico di Torino

In this work, we developed and characterized bio-based formulations derived from functionalized vegetable oils, aiming to create sustainable vitrimeric resins suitable for 3D printing. Epoxidized castor oil (ECO), known for its inherent vitrimeric behaviour due to the presence of hydroxyl groups enabling transesterification, was used as the primary component. However, its high viscosity at room temperature limits its printability. To address this, epoxidized soybean oil (ESO), a less viscous and equally bio-based alternative, was blended with ECO in varying weight ratios: 100% ECO, 100% ESO, ECO:ESO 70:30, and ECO:ESO 50:50. UV-curing characterizations of the prepared formulations were performed through FTIR and photo-DSC. Their thermal and mechanical properties were investigated through DMTA and tensile tests, while rheological analyses assessed their printability. Vitrimeric behaviour was evaluated via stress relaxation tests in the presence of a biobased transesterification catalyst eugenol-based phosphate ester (EUGP). Among the blends, the ECO:ESO 70:30 formulation retained a good vitrimeric dynamics, while in the 50:50 blend this feature decreased due to the lack of hydroxyl groups in ESO. The vitrimeric systems demonstrated successful 3D printability and were proven to be reprocessable both thermally and chemically. This work highlights the potential of renewable, plant-oil-based materials in advancing circular, sustainable additive manufacturing technologies.

Development of Parallax Volumetric Additive Manufacturing for Rapid, Large-Area 3D Fabrication

Chi Chung Li, University of Colorado Boulder

Volumetric additive manufacturing (VAM) is an emerging technology that enables the rapid creation of complex 3D freeform structures directly within photoresin by simultaneously exposing all points of the target geometry in parallel. VAM offers numerous advantages, including state-of-the-art fabrication speed, a mechanically stable and self-supporting printing environment, and the ability to create structures on top of prebuilt objects. However, current VAM methods require light to be delivered tomographically from the sides of the object, which imposes a strong limitation on achievable lateral size and hinders scalability for large-area applications. To address this constraint, we introduce a new approach—Parallax VAM—that circumvents horizontal scalability issues by delivering all exposure light in a top-down or bottom-up manner. This novel configuration eliminates the need to rotate the material container and enables the fabrication of extremely wide, aperiodic structures. As a result, this approach to volumetric 3D printing unlocks many new applications in both industrial and research settings. In this presentation, we discuss our development progress in Parallax VAM, showcase its current capabilities, and highlight several practical challenges for widespread adoption.

Photochemistry to the rescue- our 8 year journey to develop a melamine primer

Tommy Haraldsson, Mercene Labs AB

Melamine formaldehyde laminate surfaces are everywhere in our homes and offices. The products made possible with this material range from very inexpensive bookshelves and cupboards to exclusive dinner tables made from high pressure laminate (HPL). The vast majority of melamine laminates are sold without surface treatment where the pattern and the texture are determined by a press plate. However, there is an increasing trend to lacquer melamine with industrial UV-coatings to improve haptics and scratch resistance. Coating melamine is easy, but making the coating stick to the chemically inert melamine surface is a challenge that until recently was not met to the full satisfaction of furniture producers. Traditional primers rely on surface energy matching, which fails if the melamine surface has been over or under cured in the press, while 2 component isocyanate primer solutions suffer from short pot life and an extended period before full adhesion is obtained, which complicates manufacturer’s logistics. We have developed a surface activator which relies on photochemical bonding to melamine via electron deficient carbon carbon double bonds. These create a charge transfer complex with a nitrogen electron lone pair and illumination with high energy UVC photons lead to a cascade of reactions ending in the creation of covalent bonds. In this presentation, I will describe the 8 year long tortuous journey to reach this solution, complete with a spectacular failure, patent opposition and, ultimately, a good commercial product in use at 5 different companies with a combined production of 100 M sq ft UV-lacquered melamine faced boards per year.

UV Curable Ultra Low Refractive Index Nano-voided Materials

Eric Nelson, 3M

This submission will describe the process of producing nano-voided materials for use as ultralow index materials. UV curable materials can be combined with non-curable materials to produce nanometer size phase separated materials. Subsequent removal of the non-curable material produces air-filled foam materials with a composite ultralow refractive index. Materials with refractive index as low as 1.15 to 1.20 have been produced by this method. The development of these materials has been mostly focused on optical applications where air gaps between optical components are required. The reaction rate and miscibility of the different materials are used to develop the pore size and foam structure. Materials with low haze (less than 1% in the visible) and very high haze (100% in the visible) can be produced by controlling the compositions and kinetics. The high haze materials have been shown to have excellent diffusing and hiding properties in many applications. However, one drawback of these nanovoided materials is their ability to absorb materials and therefore increase their refractive index. Development of a method to seal the top surface of the coating during the manufacturing process will be demonstrated. Sealing the surface allows conventional pressure sensitive adhesive to be used to join the ultralow index materials to other films producing laminated structures with air gap properties.

Regulating polymer properties through combined covalent and physical network structure

Jeff Stansbury, University of Colorado

The goal of this study is to develop a better understanding of how an integrated monomer design and comonomer selection strategy in photocurable formulations can be employed to achieve favorable properties in both the monomeric and polymeric states. To approach this, we use urethane-based monomers and oligomers with systematically varied urethane group number and placement. These will be combined with mono- or di-vinyl monourethane monomers that contribute to significant reductions in viscosity while also providing control of overall urethane content, reactive group concentration and covalent network density. Reduced covalent crosslink densities tend to limit polymer modulus and strength potential but here, we incorporate comonomers with specific affinities for urethane group hydrogen bonding that promote further reductions in pre-cure viscosity. This also provides a pathway for noncovalent reinforcement in the photopolymers that allows lower covalent network density while maintaining or enhancing polymeric mechanical properties. Taken together, this work demonstrates a method to achieve high-performance formulations that allow polymer strength and stiffness to be raised in parallel with increased toughness. Results with conventional and novel materials will be displayed in addition to highlighting analytical characterization techniques that purposely target critical material properties.

Photomediated Synthesis of Ultra‚ÄëHigh Molecular Weight Polymers for Advanced and Programmable Circular Materials

Brent Sumerlin, University of Florida

We report a photomediated polymerization strategy that uses only mild UV or visible light irradiation of thiocarbonylthio compounds to access ultra-high molecular weight (UHMW) block polymers, semi telechelic polymers, and polymer–protein conjugates. This method achieves number average molecular weights exceeding 10^7 g/mol and degrees of polymerization over 100,000 Рrepresenting the highest molecular weights attained via living polymerization to date. These UHMW polymers are effective in applications such as pressure-sensitive adhesives, thermally conductive materials, and mucin mimetics. Remarkably, the same photochemistry also enables controlled depolymerization back to monomers, paving the way for recyclable, low-energy polymer life-cycle management and subtractive manufacturing processes. This illustrates a powerful concept of “programmable” polymer design for sustainable, circular materials.

Photopolymer Challenges for Volumetric Additive Manufacturing

Robert McLeod, University of Colorado Boulder

Vat photopolymerization techniques such as stereolithography and digital light projection have driven optimization of photopolymers to meet processing (e.g. low viscosity, fast curing, large dark conversion) and final property (e.g. modulus, toughness, biocompatibility) requirements. The rapidly developing field of volumetric additive manufacturing (VAM) presents new material opportunities and challenges for the photopolymer field. Challenges include shrinkage and the subsequent densification because this leads to sinking of unsupported parts. Since VAM fabricates entire parts dramatically faster than layer-by-layer methods, the exotherm of reaction is proportionally more important to manage. Haze and refractive index changes induced by conversion can interfere with the light delivery into the resin volume. Conversely, some requirements like viscosity are relaxed since no resin need move, allowing printing even into solids. I will review recent advances in VAM architectures including one created by my research group, Parallax Manufacturing. I will contrast the fabrication results of these systems with traditional layer-by-layer methods. These examples will illustrate opportunities for photopolymer chemistry and processing for this new paradigm of additive manufacturing.

Spatial Control of Thiol-Ene Curing Kinetics by Antagonistic Photoreactions

Thomas Griesser, University of Leoben

The use of two wavelengths to activate different photoreactions in a resin system has recently attracted much attention in the scientific community.[1] In this contribution, antagonistic photochemistry is employed to enable spatial control over the curing kinetics of a thiol-ene photopolymerization. Thiol-ene networks are known for their excellent biocompatibility and toughness, making them attractive alternatives to conventional (meth)acrylate systems.[2] However, the application of previously reported antagonistic concepts—such as the selective termination of radical polymerizations through radical recombination—remains questionable in thiol-based systems due to radical transfer reactions.[3] Prior studies by Bowman et al. have shown that amines can exert a retarding effect on the thiol-ene reaction. Based on these findings, a photo latent base was utilized to inhibit thiol-ene photopolymerization triggered with UV light of 365 nm. This antagonistic mechanism allows for spatial modulation of curing kinetics through selective light exposure. Using two wavelength laser writing experiments, a sub-micron resolution with feature sizes below 0.5 µm was achieved, while gray-scale patterning enabled continuous tuning of polymerization kinetics. Importantly, several ene monomers were shown to undergo successful photobase-induced inhibition, indicating the broader applicability of this concept. In summary, a dual-wavelength, antagonistic photoreactive system was developed, enabling spatially resolved inhibition and modulation of thiol-ene polymerization with potential for advanced photofabrication techniques such as interference lithography.

Switching between Cationic and Radical Polymerizations

Brett Fors, Cornell University

Synthetic polymers are of significant importance in all aspects of modern life, and during the last few decades, these materials have facilitated major societal advances. Innovative polymeric materials have the potential to address humankind’s next grand scientific and technological challenges; however, taking advantage of the opportunities presented by these materials requires new methods for gaining precise control of polymer structure and function. To address this challenge, our research group focuses on the development of new synthetic methods and catalyst systems to control polymer architecture, composition, and function to yield next-generation materials. This presentation will detail the development of methods that enable switching of polymerization mechanism and monomer selectivity using external stimuli to control polymer structure and function. Additionally, recent discoveries in our group on controlled cationic polymerizations that can be run open to the air without monomer purification will be discussed. These new methods enable the streamlined synthesis of polymeric materials with precisely controlled structures.

Thiol-based coatings enhance the optical properties of elastomers fabricated with VAT photopolymerization for medical applications

Alan Aguirre-Soto, Tecnologico de Monterrey

An ideal vascular phantom should be anatomically accurate, have mechanical properties as close as possible to the tissue, and be sufficiently transparent for ease of visualization. However, materials that enable the convergence of these characteristics have remained elusive. The fabrication of patient-specific vascular phantoms with high anatomical fidelity, optical transparency, and mechanical properties close to those of vascular tissue is reported. These final properties are achieved with patient-specific vascular replicas fabricated through vat photopolymerization with commercial elastomeric acrylic-based resins before coating them with thiol-based photopolymerizable resins. A PETMP/allyl glycerol ether (AGE)/polyethylene glycol diacrylate (PEGDA) coating with a 30/70% AGE/PEGDA ratio applied on a flexible resin yielded elastic modulus, UTS, and elongation of 3.41 MPa, 1.76 MPa, and 63.2%, respectively, in range with the human aortic wall. The PETMP/AGE/PEGDA coating doubled the optical transmission from 40% to 80%, approaching 88% of the benchmark silicone-based elastomer. Higher transparency correlates with a decrease in surface roughness from 2000 to 90 nm after coating. Coated 3D-printed anatomical replicas are showcased for pre-procedural planning and medical training with good radio-opacity and echogenicity. Thiol-click chemistry coatings, as a surface treatment for elastomeric stereolithographic 3D-printed objects, address inherent limitations of photopolymer-based additive manufacturing.

Digital Light Processing of Bio-Derived Conductive Composites with Joule-Heating Capabilities

Alberto Cellai, Politecnico di Torino

This study explores the development of sustainable, smart materials for 3D printing by combining bio-based chemistry with functional performances. A photocurable acrylate polyglycerol monomer, derived from renewable sources such as saponified vegetable oils or microbial fermentation, was used to create photopolymerizable resins, suitable for Digital Light Processing (DLP). To introduce functionality, various conductive fillers,including silver, copper, nickel powders, and recycled carbon fibers (RCF), were incorporated into the resin. These additions enable electrical conductivity and the potential for heat generation through the Joule effect, opening up opportunities for smart, responsive devices. A comprehensive set of characterization techniques, including FT-IR, photo-DSC, rheology, DMTA, electrical conductivity tests, and thermal imaging, revealed that while higher filler contents increase viscosity and slightly reduce polymerization rates, they significantly boost electrical performance. In particular, Ag and RCF fillers allowed for efficient, homogeneous heating of the printed parts under low voltages. To demonstrate the potential for real-world applications, a wearable smart ring was 3D-printed using a formulation with 50 wt% silver. The device reached surface temperatures of around 60 °C with an applied voltage as low as 1–3 V, showcasing the feasibility of using these materials in custom-designed electronic or medical devices. Overall, this work highlights a promising route toward functional, sustainable 3D-printed components using bio-based photopolymers and conductive fillers.

Sub-optical stress field analysis in heterogeneous polymer films

Lewis Cox, Montana State University

Orthogonal actinic resins provide a spatial control over network topology that has revitalized long-standing engineering interests in stress transfer across dissimilar material interfaces, the critical concept underpinning structural failure and fracture. Mapping a stress field in heterogeneous media requires spatial correlation of displacement gradients and mechanical properties. Characterizing this information becomes complicated when relevant stress fields occur across sub-optical length scales. Digital image correlation (DIC) of atomic force microscopy (AFM) topography scans has traditionally been used to obtain sub-optical displacement gradients, although it has been limited by challenges associated with feature contrast and noise, and fast acquisition of force displacement measurements can now be used to provide high resolution maps of mechanical properties. This talk navigates the challenges associated with stress field mapping and establishes simple protocols for others to follow. Specifically, we demonstrate that DIC of tapping mode error (amplitude) channels enable displacements of sub-nanometer surface textures to be tracked, circumventing traditional challenges with feature contrast and noise filtering. We articulate a simple methodology for quantifying suitable DIC subset and step sizes for AFM images using free power spectral density analysis tools. Finally, a process for overlaying mechanical properties onto DIC-generated strain fields is presented and the complications associated with application of the technique to viscoelastic materials is discussed.

Sustainable UV-Cured polymer: from coatings to composites and additive manufacturing

Marco Sangermano, Politecnico di Torino

Biobased monomers are becoming increasingly important to develop green products to substitute petroleum-based materials [1]. In this study different biobased monomers have been synthesized and exploited both in cationic and radical UV-Curing [2]. Reactivity of curing process was investigated, and the crosslinked materials fully characterized. An easy tailoring of the properties of the final UV-cured coatings is demonstrated by varying the ratio of the monofunctional-difunctional epoxy monomer or by in-situ generation of hybrid organic-inorganic networks. The same formulations were processed in 3D-printing using the hot-lithography technique when processing epoxy monomers [3]. Curing and printability conditions have been defined and the printed object fully characterized. Finally, UV-Cured composites were achieved by exploiting the frontal induced photopolymerization process [4]. This technique allowed to exploit UV-Curing also to achieve thick composites.

Kinetic modeling of diffusion-limited thiol-ene photopolymerization

Yunfeng Hu, University of Colorado Boulder

Thiol-ene photopolymerizations are widely used, yet their behavior under diffusion-limited conditions remains poorly understood and underexplored in kinetic modeling. A reaction kinetic model integrating free volume theory was developed to elucidate diffusion-controlled kinetics and quantitatively predict the ultimate functional group conversion in radical-mediated thiol-ene step-growth photopolymerizations. The glass transition temperature (Tg) of the reaction mixture was experimentally correlated with monomer conversion using a combination of photo-DSC and temperature-sweep DSC. The Tg values at 0% and 100% conversion were incorporated into the kinetic framework to model free volume evolution during polymerization, resulting in highly accurate predictions of both the reaction rate and final conversion—within 5% of experimental measurements. Using this model, we systematically evaluated the influence of crosslinking density, reaction temperature, and plasticizer loading on polymerization behavior. This model was further applied to simulate the spatial and temporal kinetics in holographic recording of photopolymers, providing critical insights for the design of high-performance holographic photopolymer systems.

Understanding reactive conversion of polymers for additive manufacturing of functional materials

Max Saccone, CU Boulder

Photopolymers can be used as scaffolds, reactors, or reactants in subsequent materials transformations that yield architected materials such as hard carbons, ceramics, and metals. To break paradigms of accessible material class and resolution, these processes typically rely on heating additively manufactured parts in a reactive environment to drive polymer decomposition and precursor conversion to target materials. However, there remain gaps in our understanding of the fundamentals of how these reactions occur, as well as gaps in our ability to fabricate certain classes of materials. This talk will explore recent progress towards understanding how polymer chemistry, reaction conditions, and reactor design influence polymer conversion processes to form inorganic materials. One example of using reactive conversions is hydrogel infusion additive manufacturing (HIAM), a technique which enables fabrication of many metals such as copper, nickel, tungsten, and multicomponent alloys from a single photoresin system using an infusion-reaction paradigm. In this process, 3D printed hydrogels are swelled with aqueous metal precursors, then calcined and reduced to create miniaturized metal replicas, enabling quick iteration, compositional tuning, and multimaterial fabrication. This infusion-reaction approach has recently been extended to create composites containing polyacrylonitrile, a conventionally hard-to-print polymer that can be pyrolyzed to form architected carbon materials with carbon yields above 40%. Synthesis of polymer-derived inorganic materials is also synergistic with novel 3D printing processes including roll-to-roll printing and microfluidic printing with continuous resin injection. Analysis of these processes has led to an extension of the canonical Jacobs working curve for situations in which photopolymer is continuously introduced through microfluidic channels. Altogether, this work provides a path for photopolymer additive manufacturing to fabricate a wide range of inorganic materials at the microscale, with applications from the biomedical to aerospace to energy fields.

Constructing and Deconstructing Thermosets with Light and Thiols: Polarity Reversal Catalysis and Dual-Trigger Strategies

Derek Patton, University of Southern Mississippi

This work demonstrates photoinduced thiol-catalyzed hydrogen abstraction and β-scission of acyclic benzylidene acetals as an innovative strategy to “command-destruct” polymer thermosets. Poly(thioether acetal) networks, synthesized via thiol-ene photopolymerization, degrade rapidly into alkyl benzoate byproducts upon light exposure, transitioning from solid to liquid within seconds. This dual-mode photochemistry enables rapid photopolymerization and photodegradation with a single light source, leveraging the distinct kinetics of radical-mediated polymerization and thiol-catalyzed β-scission. The process relies on stoichiometrically imbalanced thiol-ene formulations, where residual free thiols in the network are essential for efficient degradation. Substituent effects were investigated to modulate photodegradation rates. Spatial control was achieved using photolithography to pattern thermoset degradation, while wavelength-selective degradation was demonstrated with a violet light-sensitive photoinitiator. Furthermore, thermal protecting groups were introduced to excess thiols, creating a dual-trigger “AND” gate requiring both heat and light for activation. This approach to photoinduced command-construct and command-destruct processes shows potential for a range of applications, including degradable adhesives, additive/subtractive manufacturing, and more broadly as environment friendly materials with well-defined end-of-use management strategies.

Kinetics-Driven Design of Next-Generation 3D Printing Materials

Sijia Huang, University of Utah

Vat photopolymerization (VP) techniques have enabled the fabrication of complex geometries by balancing high precision with fast processing speeds. However, current VP techniques still face several challenges, including limited design freedom for unsupported features, restricted material selections, and the absence of in-situ monitoring techniques to better understand the printing process. To address these limitations, I will discuss our recent efforts in engineering chemical reactions to close these gaps. Specifically, I will introduce a newly designed orthogonal chemistry framework for printing a base-degradable thermoset, allowing support structures to be patterned in a one-pot formulation alongside the primary structural material. This approach enables dual-wavelength patterning of sacrificial thermoset supports, expanding the range of accessible 3D-printable materials and geometries. In addition, I will present a new digital twin platform for 2D and 3D visualization of reaction kinetics in additive manufacturing, which opens new possibilities in precision fabrication and functional material design.

Shape-morphing particles from photocrosslinkable copolymer films

Ryan Hayward, University of Colorado

Photocrosslinkable polymer films based on copolymers containing pendent benzophenone moieties have proven to be a versatile system for defining stimuli-responsive shape-morphing materials. In particular, this system allows for spatial definition of crosslink density within swellable hydrogel materials, and/or of multiple materials with varying properties. While our past studies have relied on these methods to fabricate millimeter-scale objects in a one-by-one fashion, we have recently focused on preparing micrometer-scale particles in a more scalable fashion using a commercial maskless lithography system. This enables production of particles with a wide variety of geometries, including cylindrical shells, spherical caps, saddles, and helical ribbons, that can be varied via changes in temperature. We are working to characterize how assembly and collective behavior of these particles are driven by changes in shape in a variety of contexts.

Aqueous PhotoATRP of Responsive Polymers from Structured Peptide Assemblies

Christopher Kloxin, University of Delaware

Photoinduced atom transfer radical polymerization (photoATRP) enables precise polymer growth under mild, aqueous conditions by generating radicals on demand with light. In this work, we used aqueous photoATRP to grow polymers directly from bundlemers, coiled-coil peptide assemblies that serve as structurally defined nanoscale scaffolds. Site-specific installation of bromoisobutyramide initiators allowed light-controlled polymerization without disrupting the native coiled-coil structure. This approach produced uniform, low-dispersity conjugates with tunable polymer lengths and responsive lower critical solution temperature (LCST) behavior. We further demonstrated sequential photoATRP and modular initiator placement to create bottlebrush-like architectures and explored their assembly using microscopy and simulations. Overall, this strategy showcases how aqueous photoATRP can combine the stability of protein nanostructures with the dynamic functionality of light-activated polymers, offering a versatile platform for designing adaptive hybrid materials.

3D printable, mechanically robust, nanostructured block copolymer hydrogels

Arkodip Mandal, University of Colorado Boulder

Tremendous advances over the past two decades in macromolecular design and network architecture and topology have led to the development of mechanically robust hydrogels, significantly expanding their applications to load-bearing implants, wearable sensors and patches, drug delivery systems, and soft-robotic actuators. Nevertheless, many of these hydrogel systems continue to suffer from key limitations, such as mechanical deterioration in physiological environments, poor fatigue resistance due to irreversible network damage, limited self-recovery at ambient conditions following deformation, lack of dissipation mechanisms, or incompatibility with advanced manufacturing techniques. Here, we overcome these limitations by designing nanostructured block copolymer (BCP) based hydrogels in a highly modular fashion from macromolecular building blocks that crosslink via thiol-ene based photoclick reactions. The hierarchical architecture of the BCP hydrogels at the nano- and meso-scales, comprising self-assembled domains and ordered grains, underpin their robust and complex mechanical response. This results in hydrogels exhibiting high modulus, high stretchability, high fracture toughness, high energy dissipation, high fatigue-resistance, and rapid, complete self-recovery under ambient conditions. Importantly, the precursors can be formulated as resins compatible with lithography-based additive manufacturing, enabling the rapid fabrication of complex 3D hydrogel architectures with high spatial resolution. This unique combination of mechanical performance, bottom-up tunability, and processibility make these BCP hydrogels attractive for diverse biomedical applications.

3D Printing of PolyHIPE Scaffolds with Bioactive Glasses: a Bio-Based Platform for Bone Tissue Regeneration

Matteo Bergoglio, Politecnico di Torino

PolyHIPEs are porous polymers fabricated using a technique known as high internal phase emulsion (HIPE) templating. This process involves polymerising monomers within an emulsion where the dispersed (internal) phase makes up at least 74% of the total volume. Polymerisation locks the emulsion structure in place, yielding a highly porous polymer with an interconnected network of voids, ideal for nutrient transport and cell infiltration in biomedical applications. This study presents the development, characterisation, and biological assessment of biobased thiol-ene polyHIPE scaffolds reinforced with bioactive glass (BG) particles for bone tissue engineering applications. The scaffolds were formulated using renewable monomers and processed via HIPE templating to achieve highly porous, interconnected structures. To enhance patient-specific adaptability, the materials were also successfully 3D printed, maintaining their porosity while introducing macroporosity into the architecture. Morphological analysis confirmed the formation of open-cell foams with interconnected pores, favourable for in situ nutrient transport and cell infiltration. Contact angle measurements showed a progressive increase in surface hydrophilicity with higher BG content, attributed to hydroxyl groups on the glass surface, an advantageous property for biological interactions. Gel content analysis indicated a highly crosslinked network, while thermogravimetric analysis (TGA) confirmed both the high thermal stability of the polymer matrix and the successful incorporation of BG. Dynamic Mechanical Thermal Analysis (DMTA) revealed a BG-dependent increase in glass transition temperature (Tg), suggesting reduced polymer chain mobility and improved stiffness. Compression testing demonstrated a substantial increase in elastic modulus with BG addition, without compromising shape-memory behaviour. Biological evaluations using MG-63 osteoblast-like cells confirmed excellent cytocompatibility for all formulations. Resazurin assays showed sustained metabolic activity and cell proliferation over 7 days. Phalloidin/DAPI staining revealed progressive cell spreading and adhesion, while OsteoImage assays conducted after 28 days indicated hydroxyapatite deposition that increased with BG content, demonstrating the osteoinductive potential of the scaffolds. Overall, the combination of 3D printability, high porosity, mechanical performance, and bioactivity makes these biobased thiol-ene polyHIPE scaffolds strong candidates for sustainable and effective bone regeneration strategies.

Production of Rare Earth Elements Using 3D Printed Ion Exchange Resins

Sophie Morton, University of Utah

Rare earth elements (REEs) are essential in a wide range of technologies from consumer electronics to medical and industrial-grade applications. Conventional solvent extraction techniques for REE recovery involve intense hydrometallurgical processing and leaching, require high solvent consumption, and generate significant chemical waste. Ion exchange resins have emerged as an alternative method in the extraction of REEs due to their durability, cost-effectiveness, and tunable selectivity. This work investigates methacrylate- and methacrylamide-based photopolymer resins synthesized with varying secondary monomers and crosslinkers to optimize ion selectivity and binding capacity. Formulations were designed to be compatible with stereolithography (SLA) 3D printing, which offers greater control over polymer architecture and lattice geometry as well as reduces curation time to seconds. Once the printed lattice structures were optimized, the samples underwent multi-cycle adsorption/desorption testing to evaluate reusability and long-term stability. The integration of customizable SLA-printed ion exchange resins demonstrates a more sustainable and efficient method for REE recovery systems.

High-Performance 3D-Printing Resins Based on Triazine Cores and Isocyanate-Free Urethane–Acid Networks

Sean Keyser, University of Colorado

Achieving both high stiffness and toughness in a single photopolymer remains a central challenge in additive manufacturing. Conventional urethane-linked networks have been used to address this, introducing hydrogen bonds that enhance toughness while retaining high modulus. However, their synthesis typically relies on toxic, petroleum-derived isocyanates. While scalable and widely used, isocyanates pose significant health and handling risks due to their reactivity and sensitization potential. Incorporating carboxylic acids alongside urethanes has been shown to further increase hydrogen bond density and improve mechanical performance, but still does not eliminate the reliance on isocyanates, limiting progress toward safer, more sustainable material platforms. This work introduces a new class of triazine-based resins that enable urethane–acid chemistry through an isocyanate-free carbonate–amine route. Rigid, multifunctional triazine cores support a modular, isocyanate-free synthetic route to urethane formation, enabling the synthesis of both homo- and hetero-functional monomers and oligomers with precise control over branching, molecular weight, and functionality. All reactions proceed under mild conditions using low-cost, scalable reagents in yields exceeding 90%, providing a flexible and tunable foundation for high-performance resin formulations. When combined with hydrogen-bonding carboxylic acid comonomers, these resins cure into photopolymer networks with dry-state moduli above 5 GPa, flexural strengths over 180 MPa, and toughness exceeding 10 MJ/m³, matching and surpassing the performance of leading commercial systems, without the use of isocyanates. This safer, tunable system advances resin design for vat and multimaterial printing, offering a viable path to high-performance additive manufacturing without isocyanates.

Surface-Initiated Photopolymerization: Exploring the Power of Germanium Photoinitiators

Christine Bandl, Technical University of Leoben

Applications and perspectives of Ge-based PI in surface initiated photopolymerization will be presented with a special focus on surface initiated free radical promoted cationic photopolymerization pathways. Ge-based photoinitiators (PI) offer several advantages over their P-based counterparts including low toxicity, high reactivity towards monomers and an extended absorption up to 480 nm enabling excitation of the PI in the visible range. Irradiation of these compounds initiates Norrish type I cleavage resulting in highly reactive germanium centered radicals (germyl radicals), which readily add to monomeric double bonds. Beyond this free radical polymerization, our latest results also show that free radical promoted cationic polymerization of monomers such as epoxides and vinylethers proceeds in the presence of iodonium salts. The respective photochemical reaction pathway was proved by chemically induced dynamic nuclear polarization spectroscopy. Both approaches are utilized for surface initiated grafting-from polymerizations, which are characterized by various techniques including FTIR, solid-state NMR, XPS, SEM, ToF-SIMS and TGA, proving the growth of polymer chains from the modified surfaces and assessing the structure of these polymers as well as the grafting densities. Due to their low toxicity, strong absorption in the visible range, and versatile reaction mechanisms, the investigated Ge-based photoinitiators (PIs) represent highly promising photoreactive systems. These properties make them well-suited for advanced applications such as dental nanocomposite resins, controlled drug release systems, cancer therapy, dye-doping, silica-coated quantum dots, and many more.

Hierarchically structured, functional coatings from photo-based processes

Caroline Szczepanski, Michigan State University

Hierarchical topography, meaning a surface with features of multiple length scales, can enhance coating performance. Specifically, hierarchical topography impacts optical properties (matte appearance, structural color), adhesion, and even allows for unique wettability regimes such as guided fluid transport or fog collection. While complex, multi-scale topography can be engineered via machining, lithography and additive manufacturing, these strategies can be limiting in terms of time, energy, and excess material waste. In this talk, I will highlight recent efforts from our team using straight-forward photopolymerizations to engineer surface topography and chemical patterning. This includes introducing heterogeneous polymerizations so multiple scales of topography form during a single UV-curing step: (1) traditional wrinkling patterns resulting from depth-wise gradients in cross-link density due to oxygen inhibition and (2) macro-scale features due to phase domains of differing stiffness. Taking this one step further, I will highlight our recent efforts at achieving transient and on-demand topographies, mainly via the use of coumarin functionalities within a coating network. We take advantage of the photo-responsive nature of coumarin (dimerization upon exposure to long wave UV (365 nm) and cleavage when exposed to short wave UV (254 nm)) to manipulate coating cross-link density, and thus the scale of surface instabilities (e.g. wrinkles) that form. I will discuss how these hierarchical, and potentially dynamic structures are of interest for smart coatings and devices.

Photo + ROMP: Using light in unique ways to control ring-opening metathesis polymerizations

Leah Appelhans, Sandia National Laboratories

Photoactivated catalysts have been extensively investigated for the initiation of ring-opening metathesis polymerization. However, much less work has been done on using light to enable active control of ROMP. Our group is investigating multiple approaches to use light to control both reaction rates and polymer composition. With catalyst-based photocontrol we demonstrate control over the front velocity and direction of propagation of a frontal ring-opening metathesis polymerization (FROMP). Frontal reactions continue propagation after initiation through a self-sustaining thermal front, and the speed and direction of a propagating front cannot be easily controlled. Using the photobase generator NPPOC-TMG and different photosensitizers we have demonstrated both acceleration and deceleration of FROMP. In addition, we can control the direction and shape of FROMP propagation in a sheet of resin. We will also share initial results on monomer-based photocontrol approaches which utilize photoisomerizable monomers to control the composition and thermomechanical properties of a FROMP copolymer, and show applications in photolithography and DIW 3D printing. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525

Molecularly engineered, light-responsive building blocks for the creation of well-defined bioinspired cellular microenvironments

April Kloxin, University of Delaware

The microenvironments of cells in the human body are known to direct cellular responses, including in healthy versus maladaptive wound healing upon injury. Accordingly, soft materials are being designed are inspired by these microenvironments, particularly the extracellular matrix (ECM) that surrounds cells, for probing and controlling cellular responses both in vitro and in vivo, from controlled multidimensional culture models for mechanistic studies to injectable materials for therapeutic delivery. In this talk, I will highlight some of our recent efforts in this arena. For example, through the design of molecularly engineered polymer and peptide building blocks, we have established synthetic ECMs that allow us to probe the response of barrier tissue cells (e.g., epithelial cells, fibroblasts, immune cells) to injury triggered upon the application of light or other stimuli. Integration of physically assembling peptides within such covalently crosslinked networks further imparts designed hierarchical, bioactive nano- and micro-structures and physiologically relevant viscoelasticity. We collaboratively are using bioprinting for the creation of well-defined 3D cultures built upon such materials with high-throughput for the evaluation of therapeutic approaches. Additionally, we are utilizing these types of bottom-up, molecularly engineered synthetic ECMs in conjunction with top-down, flow-based systems for the production of injectable delivery vehicles and cell-based therapies.

Photopolymerization of Liquid Crystalline Phases for Structurally Programmed Optical Materials

Timothy White, University of Colorado Boulder

The self-organizing behavior of liquid crystalline phases offers a powerful framework for fabricating optical materials with periodic structures on the scale of visible and near-infrared light. In this presentation, I will describe photopolymerization-based strategies to prepare solid-state optical elements from cholesteric and blue phase liquid crystals, as well as nematic phases patterned via photoalignment. These materials exploit the intrinsic periodicity and birefringence of liquid crystalline order to produce reflection, diffraction, and polarization-selective properties in thin, photopolymerized films. Cholesteric liquid crystals, with their helical supramolecular organization, serve as tunable Bragg reflectors whose reflection bandwidth, handedness, and angular response can be precisely controlled through composition and polymerization conditions. Blue phase liquid crystals, which form three-dimensional cubic structures with nanoscale periodicity, offer isotropic yet diffractive behavior suitable for fast-switching photonic applications. Additionally, photoalignment of nematic phases provides a route to encode spatially varying director fields prior to polymerization, enabling the fabrication of polarization gratings and other diffractive optical elements with high fidelity. Emphasis will be placed on UV-curable reactive mesogens and polymer-stabilization strategies that lock in delicate liquid crystal architectures while preserving their optical function. These approaches support scalable, mask-based fabrication of flat, flexible, and responsive optical films. The resulting photopolymerized materials have applications in reflective displays, laser beam shaping, AR/VR optics, and tunable filters—highlighting the role of photopolymerization as a tool for translating soft molecular order into robust optical function.

TBD

Stephanie Bryant, University of Colorado Boulder

Development of polyamide in photo-curable materials

Chen Wang, University of Utah

Photopolymers are ubiquitous materials for coatings, adhesives, 3D printing, and many other rapidly growing applications. Today’s photopolymer market is calling for improved materials performance, as well as enhanced sustainability such as adopting renewable chemicals. In this talk, we demonstrate amides as a performance-advantaged functional group over urethanes, in the design of rapidly photopolymerizable resins. Our crosslinked polyamides synthesized from step-growth photopolymerization exhibited high toughness, e.g. >100% elongation-at-break, > 1GPa Young’s modulus, and >40 MPa tensile yield strength, a performance typically only attainable from semicrystalline thermoplastics. Further, we discuss achieving semicrystallinity in the network photopolymers. By incorporating amide groups and hydrogen bonding, the enhanced backbone rigidity raised glass transition temperatures by 35-40 °C compared to a polyester control group. In the crystalline domain, the hydrogen bonding raised equilibrium melting temperatures by 60 °C, but reduced melting enthalpy. We also find that hydrogen bonding did not alter the threshold of chain length between crosslinks for crystallization (>2,500 g/mol).

Kinetic Control of Photochemical Reactions Enables the Fabrication of Reprogrammable Gels

Manuela Garay-Sarmiento, University of Colorado Boulder, BioFrontiers

Native tissues undergo dynamic changes in shape and mechanical properties, particularly during tissue development and disease progression. Gels capable of recapitulating such dynamic properties (e.g., local stiffness, shape morphology) are gaining significant interest to understand and guide cellular behavior. Light-responsive materials are of particular interest since light can be delivered remotely and with high precision, enabling spatiotemporal control during reprogramming. Furthermore, Digital Light Processing (DLP) has emerged as a promising technique to fabricate gels with complex 3D structures that more accurately mimic the structural complexity and heterogeneity of native tissues. To avoid consumption of photosensitive groups during DLP printing, we leverage the kinetic specificity of methacrylate homopolymerizations and dithiolane (DL)-ene reactions. This allows the formation of objects from photoreactive resins via DLP with methacrylate crosslinking and preservation of photoresponsive DL groups for subsequent light-based stiffening on demand. DLP printed gels can be reproducibly post stiffened up to 10-fold, dynamically replicating the mechanical properties of a broad range of healthy and diseased tissues. Such precise spatial control over stiffness enables the creation of complex shape transformations—such as bending and twisting—based on how the stiffness gradients are designed across the material. Importantly, the post stiffening process occurs under mild conditions, without the need for photoinitiators or high light intensities, making it ideal for future live-cell studies and advanced mechanobiology applications.

Effect of Functional Groups on Acrylate Photopolymerization Kinetics during UV Cure

Robin Crownover, US Army DEVCOM AC

It has been previously shown that monoacrylate secondary functionalities have a profound effect on the photopolymerization kinetics of these materials. While the previous research showed a polymerization rate increase with the addition of specific secondary functionalities, we have identified alternative secondary functionalities that reduce the polymerization kinetics. Based on their electron density and degree of electronegativity, it would be expected that these functional groups would have increased photopolymerization rates. This study therefore investigates these functional groups in comparison with other well-studied functional groups in an attempt to understand the mechanistic reasons these functional groups reduce photopolymerization kinetics. By slowing photoinitiation, all differences in photopolymerization rates are exaggerated, allowing for subtle differences in kinetics to be observed and further insight into the effects of the functional groups on polymerization to be seen. In addition to comparing ethyl spaced functional groups, the spacing between the acrylate group and secondary functionality was increased, which further slowed polymerization rate to a degree beyond what was expected from other functional groups.

Type III Photopolymerization as a new Paradigm for Light-Based 3D Printing

Zachariah Page, The University of Texas at Austin

Light has revolutionized the creation of polymers, enabling groundbreaking technologies in imaging, lithography, adhesives, and 3D printing. Its effectiveness stems from the unmatched precision in controlling chemical reactions both in time and space. Traditional methods, however, rely on high-energy ultraviolet (UV) light (wavelengths below 400 nm), which is ubiquitously absorbed and scattered, which can lead to degradation and a loss in spatial resolution. These issues limit the range of materials compatible with UV-based polymer creation techniques. Excitingly, the recent commercialization of affordable light emitting diodes (LEDs) has paved the way for exploring gentler, visible light-triggered reactions in polymer production. This presentaton will focus on how the ZAP Research Group has contributed to the development of rapid photopolymerization chemistry from a fundamnetal perspective. The discussion will cover the “evolution” of visible light-induced polymerizations from the following mechanisms: 1) Type I: One component photoinitiation РDirect light absorption leading to bond scission to 2) Type II: Two component photo-redox catalysis РLight-driven electron transfer processes and finally 3) Type III: Three component triplet fusion upconversion РConverting lower-energy photons to higher-energy ones. One of our primary objectives with these processes is to enable projection-based 3D printing that require rapid photopolymerizations (curing in less than 60 seconds), good shelf stability in the absence of light (temporal control), and high sensitivity to react with low-intensity LED exposure (less than 50 mW/cm²). These advancements aim to make visible light polymerization more practical, efficient, and widely applicable in various industries.

Arts and crafts by photopolymerization: programming complex actuation in liquid crystalline elastomers

Tayler Hebner, Purdue University

Liquid crystalline elastomers (LCEs) are stimuli-responsive polymers that are often programmed to undergo reversible, large-magnitude deformations. The deformations exhibited by these materials are a result of an order disruption between liquid crystalline mesogens incorporated in the polymer network. Programming complex modes of deformation in LCEs requires patterning of the alignment of the liquid crystalline mesogens, and crosslinks in the polymer network are often used to retain this alignment in the freestanding LCE. Notably, the properties of the crosslinked network are also correlated to actuation properties such as phase transition temperatures and deformation magnitude. Therefore, control of network topology in the crosslinking step enables control over the functional properties of the LCE. As such, photopolymerization is often used as a crosslinking step in LCE fabrication as it enables spatiotemporal control and many combinations of initiator and monomer components are available to tune final network structure. In this work, we specifically focus on thiol-acrylate photopolymerization for crosslinking in LCEs, which produces networks with pendant thiol groups and creates opportunities for post-functionalization of the material. We demonstrate that a secondary spatially-controlled photopolymerization step that leverages these pendant thiols enables patterning of complex deformations based on spatial discrepancies in crosslink density. In another instance, we show that secondary photopolymerization leveraging the pendant thiols enables lamination of LCEs with contrasting properties to produce snap-through actuation. Overall, these studies demonstrate that fundamental understanding and control over network formation via photopolymerization are powerful tools for complex and creative programming of LCE actuators.

Design and Properties of Controlled Liquid Crystal Elastomer Networks

Emily Davidson, Princeton University

We study a series of liquid crystal elastomers photopolymerized from precursor oligomers to understand the coupling between LCE network structure and material properties. The results elucidate the intrinsic competition that arises between network composition and crosslink density in tuning the nematic-to-isotropic transition temperatures of these materials. We also examine how both the sharpness of the transition and soft elasticity are controlled by the structure of the network itself. Finally, we examine networks polymerized from fractionated liquid crystalline oligomers with narrow molecular weight distributions.

Photo-responsive Dynamic Networks

Stuart Rowan, University of Chicago

The dynamic bond can be defined as any class of bond that selectively undergoes reversible breaking and reformation, usually under equilibrium conditions. The incorporation of dynamic bonds (which can be either covalent or non-covalent) allows access to structurally dynamic polymers and composites. These materials can exhibit macroscopic responses to environmental stimuli due to the rearrangement of their polymeric architecture. The nature of the dynamic bond not only determines the stimulus the material responds to but also influences the response itself. This design concept represents a molecular-level approach to developing new stimuli-responsive/adaptive materials. We have been exploring photo-responsive dynamic bonds to access new material platforms and have developed a range of mechanically stable, structurally dynamic polymer and nanocomposite films that change their properties in response to light. These adaptive materials have potential applications in healable plastics, responsive liquid crystalline polymers, adhesives, chemical sensors, shape memory materials, and ion conducting systems. Our latest results in these areas will be discussed.

Dithiolane (Co)polymers and Their Potential Applications

Christopher Bowman, University of Colorado Boulder

As additive manufacturing technologies continue to advance, the challenge of recycling printed components persists. Crosslinked polymers remain the material of choice in light-based additive manufacturing due to their fast gelation kinetics and shape stability after crosslinking. However, their permanently crosslinked structure hinders recycling or remolding unless dynamic bonds are present. Covalent adaptable networks (CANs) address this limitation through the incorporation of dynamic bonds at the crosslinks, enabling facile reprocessability. Recently, 1,2-dithiolanes, a five-membered cyclic disulfide, have emerged as a promising dynamic chemistry in polymer. Dithiolanes undergo a ring-opening polymerization, resulting in linear disulfides and enabling the formation of dynamic bonds directly through the crosslinking reaction. Here, we introduce a tetrafunctional dithiolane monomer, lipoic acid pentaerythritol ethoxylate, which can be photopolymerized and is compatible with high-resolution light-based additive manufacturing across multiple length scales. Additionally, this monomer can depolymerize back to its original ring-closed form through heating and solvent dilution, allowing for repolymerization. Furthermore, through a post-polymerization disulfidation reaction with a monofunctional vinyl, the dynamic character of these materials can be modulated. This work represents an advancement in the development of multifunctional dithiolane monomers and recyclable resins for additive manufacturing.