Optofluidic maskless lithography technique that can dynamically synthesize free-floating polymeric microstructures inside microfluidic channels by selectively polymerizing photocurable resin with high-speed two-dimensional spatial light modulators. The combination of programable optical projection and microfluidic devices allows one to precisely control the timing and location of the photopolymerization process for microstructure fabrication. Real-time generation of microparticles with various shapes, sizes, ordering, and material contents are experimentally demonstrated. Long polymeric structures of which size is not limited by the exposure field of view can also be fabricated. 

Highly programmable marangoni microswimmers driven by the Marangoni effect that can self-propel on the surface of water. Previous studies on Marangoni swimmers have shown the advantage of self-propulsion without external energy source or mechanical systems, by taking advantage of direct conversion from power source materials to mechanical energy. However, current developments on Marangoni microswimmers have limitations in their fabrication, thereby hindering their programmability and precise mass production. By introducing a photopatterning method, we generated Marangoni microswimmers with multiple functional parts with distinct material properties in high throughput. Furthermore, various motions such as time-dependent direction change and disassembly of swimmers without external stimuli are programmed into the Marangoni microswimmers.

Sophisticated three-dimensional (3D) structures found in nature are self-organized by bottom-up natural processes. To artificially construct these complex systems, various bottom-up fabrication methods, designed to transform 2D structures into 3D structures, have been developed as alternatives to conventional top-down lithography processes. We present a different self-organization approach, where we construct microstructures with periodic and ordered, but with random architecture, like mazes. For this purpose, we transformed planar surfaces using wrinkling to directly use randomly generated ridges as maze walls. Highly regular maze structures, consisting of several tessellations with customized designs, were fabricated by precisely controlling wrinkling with the ridge-guiding structure, analogous to the creases in origami. The method presented here could have widespread applications in various material systems with multiple length scales.

The 3D printing apparatus in conventional inkjet and stereolithography systems is limited to continuous fabrication of a microsized three-dimensional hydrogel composed of multiple substances. We present a micro three-dimensional printing system by combining a polydimethylsiloxane microfluidic channel through which various fluids can flow into a micro two-dimensional particle generation system, and a single-axis stepper motor to control the thickness of each layer. The optimal channel designs for micro three-dimensional printing were set up through a physics simulation program and using the simulation analysis, the optimal microfluidic channel was fabricated. Through the system and channel, three-dimensional micropatterns and particles could be fabricated and the generated microparticles automatically collected by the washing flow in the channel. Zinc oxide nanoparticle materials transparent, biocompatible, and capable of absorbing ultraviolet light were added to the premixed photocurable solution used for the microparticle production, and thereby precise micro three-dimensional patterns and particles could be fabricated. In addition, by transporting a variety of fluids into the microfluidic channel, it was possible to create micro three-dimensional particles composed of heterogeneous materials.