Generation of 3D microparticles in non-rectangular cross-section microchannels

Abstract

3D microparticles have been expected to apply in various fields including tissue engineering, MEMS, and optics. Despite the arduous research, it is still difficult to change the shapes regarding the z-axis due to rectan-gular cross-section channels. We replaced morphology of microchannels in a different manner compared to previous rectangular cross-section microchannels. Microchannels with non-rectangular cross-section were fabricated by a variety of microfabrication techniques. Semi-circular cross-section microchannels were made by using reflow phenomena characteristics of positive photoresist(PR) at high temperatures. KOH solution etched silicon anisotropically and triangular cross-section were made. To manage the angles of cross-section and form varied shapes, tilted UV lithography was used. These methods enabled the microchannels to gener-ate various shapes of 3D particles with high resolution. Microfluidic pneumatic control system was used to guarantee high throughput in the methods referred to in the past. Optofluidic lithography maskless system was used to alter the shapes of UV exposure in real time. In this study, patterned UV light was illuminated to fit width of channels in order to utilize the most of the channel morphology. We confirmed how and where particles were generated by comparing generated particles with results of modeling. And Multi-functional Janus particles were generated in a Y-shaped channel to prove broad availability of 3D shaped microparticles. Tilted UV lithography technique have a potential to figure out dynamics of microparticles in microchannels with various shaped cross-section. Also 3D microparticles can be applied to on drug delivery system and barcodes for diagnosis.