Material-Efficient Multimaterial Projection Micro-stereolithography Using Droplet-Based Resin Supply

This paper presents a material-efficient multimaterial projection micro-stereolithography (PμSL), a digital light processing (DLP) additive manufacturing process for printing microstructures. We present a droplet-based resin supply system to address the issue of excessive material waste of the multimaterial PμSL. By depositing droplets of different liquid resins, 3D printing of a microstructure can still be performed without the need for a traditional vat while printing materials can be switched with minimal material consumption. Precise control of small droplet volume is obtained by pressure control of the resin injection nozzles, exact opening times of fluid valves, and appropriate surface coatings in order to portion droplets so that just enough material is brought to the build area. Since PμSL enables micro 3D printing (in-plane resolution of 76 μm), PμSL using droplet-based resin supply module provides multimaterial micro 3D printing with low material consumption. Also reported is that material bleeding, which degrades the printing resolution during multimaterial printing, can be minimized by using a cleaning droplet system. We present 3D printing of highly complex multimaterial 3D microstructures using three different photocurable polymers, demonstrating a material efficiency of 11.4%, which is 500 times higher than that of a previously reported PμSL process using dynamic fluidic control.