Surface Free Energy Regulation Enabling High-Efficiency Material Utilization in Surface Tension-Confined DLP Technology.

Enhancing material utilization in digital light processing (DLP) technology is crucial for cost reduction and efficiency gains when employing photosensitive hydrogel inks containing functional materials. This study focuses on pushing the limits of material utilization in surface tension-confined DLP technology by regulating surface free energy. By thoroughly analyzing the interfacial properties among substrates, release films, and hydrogel samples, we established a comprehensive interfacial optimization strategy through surface energy modulation, solid/liquid interface adhesion optimization, and model-based structural design. Results demonstrated that locally hydrophobic treatment of the 1060 aluminum substrate to reduce its surface free energy, coupled with locally hydrophilic treatment of the release film to increase its surface free energy, effectively confined hydrogel solution inside the printing area and significantly improved material utilization. For rectangular structures, the optimized printing system achieves 85.4% material utilization at a solution volume of 0.6 mL, representing an 38% improvement over previous approaches. Lower volumes (0.01-0.4 mL) showed improvements ranging from 10% to 24%. This work provides both a theoretical foundation and a feasible technical solution for DLP printing of hydrogels with high material utilization.