ERI: Improving the Vat Photopolymerization 3D-Printing of Soft Elastomers Through a Deeper Understanding of Process Dynamics

This Engineering Research Initiation (ERI) award supports fundamental research on improving the additive manufacturing of soft elastomers. While better performing soft materials are being developed for additive manufacturing, the quality and fidelity of the printed parts remains extremely poor which prevents their use in functional applications such as biomedical devices and soft robotics. The lack of quality arises from a critical knowledge gap in understanding the fundamental additive manufacturing process dynamics. This project seeks to address this knowledge gap by developing two novel experimental techniques to uncover these fundamental process dynamics. Establishing the foundational science behind the additive manufacturing of soft elastomers intends to help achieve high-fidelity printing of soft elastomers, reduce printing failures, eliminate part warping, and reliably produce fine features. This interdisciplinary work looks to help advance additive manufacturing as a whole and enable the fabrication of many technologically important structures and devices. Specifically, customized parts that match the stiffness of tissue for biomedical applications such as patient-specific implants, soft prosthetics, and surgical models, can be developed to improve patient outcomes and help address real world health challenges. Beyond the scientific advancements, this project looks to provide valuable hands-on research opportunities for students, integrate research findings into the curriculum, and engage K-12 students through interactive workshops on additive manufacturing and soft materials. These activities will foster a new generation of engineers and scientists enthusiastic about advanced manufacturing in an EPSCoR jurisdiction and contribute to a globally competitive STEM workforce. The main objective of this research is to elucidate the fundamental process dynamics governing the Vat Photopolymerization Additive Manufacturing of soft elastomers through the development of two new experimental approaches. The central hypothesis is that the printing quality of soft elastomers is based on two related factors- (1) the curing rate (i.e. the development of modulus over time during photocuring) and (2) the adhesion forces during the recoating process. The first research aim looks to develop a photorheology-based experiment to quantify the adhesion forces and investigate their relationship with printing parameters and resin formulation. The second aim seeks to develop an in-situ X-ray photon correlation spectroscopy experiment to characterize the spatially localized material evolution during photocuring, providing new insights at a microscale resolution. Finally, the third aim looks to synthesize the data and relationships discovered with the new experimental methods to construct processing maps that identify printing parameters and material properties that result in high-fidelity printing. These maps intend to guide the selection of optimal printing parameters and inform resin design to produce functional soft parts that will help address real world health challenges. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.