Pneumatically controlled multi-level microchannel for separation and extraction of microparticles

Most microfluidic devices are fabricated by using standard photolithography technology so that they are typically limited to a single, uniform microchannel depth. In this work, we employ a polydimethylsiloxane (PDMS) gray-scale photomask (PGSP) developed in our previous work for fabricating multi-level microchannels (MLMs) that hold a high potential for enhancing the separation performance and efficiency of microparticles. Since the PGSP provides a series of multiple, uniform and precise filter gaps in a microchannel, we describe an MLM-integrated microfluidic device that not only filters but also accumulates microparticles by size such as polystyrene beads and yeast cells. In addition, we integrate a pneumatic pressure controller that manually manipulates the filter gaps to enable sequential extraction of the separated, accumulated microparticles from the device for additional post-analysis. Since the PGSP-based soft-lithography technology provides a simple but powerful fabrication method for MLMs, we believe that both the fabrication method and the separation and extraction device can be widely used for micro total analysis systems that benefit from MLMs.