Characterizing the separation behavior of photocurable PDMS on a hydrogel film during vat photopolymerization: A benchmark study

The separation between printed part and vat floor in constrained surface vat photopolymerization (VP) is a long-standing challenge, which limits the printability of soft materials like polydimethylsiloxane (PDMS). This study aims to characterize the separation behavior of a photocurable PDMS resin on a hydrogel film whose high-water content is expected to minimize the separation force. For this benchmark study, a commercially available polytetrafluoroethylene (PTFE) and an acrylate-based photopolymer are used as the baselines. Along with two printing speeds, a total of eight cases (two films, two resins, and two speeds) are used in the design of the experiment. A modified digital light processing (DLP) printing with a built-in force sensor is used to sample the force profile during the printing. The results show that PDMS has a lower separation force but longer separation distance than those of the acrylate-based resin. The hydrogel film can further minimize the separation force and distance; those values are under 0.5 N in PDMS printing. A lower speed can further reduce the separation force, but increase separation distance, likely due to the rate-dependent material properties. These results suggest a potential solution to print PDMS fast with small and fragile features.