AccScience Publishing / ESAM / Volume 2 / Issue 1 / DOI: 10.36922/ESAM026080004
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ORIGINAL RESEARCH ARTICLE

Dual-wavelength photoinhibition-aided vat photopolymerization (PinVPP) of bio-based polymers and functional hydrogels

Yousra Bensouda1 ,  Xiayun Zhao1*
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1 ZXY Intelligent Precision – Advanced Manufacturing (ZIP-AM) Laboratory, Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
ESAM 2026, 2(1), 026080004 https://doi.org/10.36922/ESAM026080004
Received: 20 February 2026 | Revised: 13 March 2026 | Accepted: 16 March 2026 | Published online: 31 March 2026
© 2026 by the Author(s). This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution 4.0 International License ( https://creativecommons.org/licenses/by/4.0/ )
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Abstract

Despite the widespread adoption of vat photopolymerization (VPP) in additive manufacturing, extending it to bio-based polymers and hydrogels remains challenging due to limited control over photopolymerization kinetics, which often leads to overcuring, surface roughness, and mechanically fragile structures—particularly in optically complex or highly fluidic materials. These issues arise largely from the intrinsic coupling of initiation and propagation in conventional single-wavelength exposure schemes. This work evaluates, for the first time, the feasibility and potential of dual-wavelength photoinhibition-aided VPP (PinVPP) as a strategy for two representative, yet fundamentally different, material classes. By spectrally decoupling visible-light initiation from UV-triggered inhibition, PinVPP enables independent regulation of radical generation and spatial confinement of curing. Using a lab-developed PinVPP platform, a bio-based polylactic acid/polyurethane acrylate (PLA–PUA) resin is investigated under independently controlled inhibition ratios, demonstrating suppression of excessive cure thickness and improved control over polymerization kinetics without compromising bulk integrity. Photo-differential scanning calorimetry, optical profilometry, and rheological analysis reveal that photoinhibition temporally redistributes polymerization, enhancing surface quality and mechanical consistency in a resin system prone to slow and uneven curing. Furthermore, applied to polyethylene glycol diacrylate (PEGDA)-based hydrogels, PinVPP reduces overcuring and shape distortion while improving surface smoothness and mechanical robustness under hydrated conditions. Raman spectroscopy quantifies local chemical conversion, and swelling, water uptake, and dimensional stability measurements confirm improved resistance to hydration-induced deformation. Overall, these results demonstrate that PinVPP expands the VPP processing envelope by introducing tunable kinetic control effective for traditionally challenging material systems, offering a scalable pathway for additive manufacturing of sustainable polymers and functional hydrogels with enhanced process stability and material performance.

Graphical abstract
Keywords
Vat photopolymerization
Photoinhibition
Bio-based polymer
Polymeric blend
Hydrogel
Digital light processing
Sustainable 3D printing
Funding
We acknowledge the fundings from the National Science Foundation under Faculty Early Career Development Award: CMMI-2238557. Any opinions, findings, and conclusions or recommendations expressed in this publication are those of the authors and do not necessarily reflect the views of the National Science Foundation.
Conflict of interest
The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Xiayun Zhao reports financial support provided by the National Science Foundation Faculty Early Career Development Program under Award ID CMMI-2238557. Xiayun Zhao is the inventor of a related patent (U.S. Patent No. 12,558,837; U.S. Application No. 17/437,343; International Application No. PCT/US20/21727), which covers aspects of two-wavelength digital light processing-based vat photopolymerization systems and methods described in this study.
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Engineering Science in Additive Manufacturing, Electronic ISSN: 3082-849X Published by AccScience Publishing
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