Handling of picoliter liquid samples in a poly(dimethylsiloxane)-based microfluidic device

Transportation, metering, and mixing of picoliter-sized liquid samples were realized in a microfluidic device with a main working area of one square millimeter. The device was constructed by sealing microfabricated grooves on a chip made of poly(dimethylsiloxane) (PDMS). Two different samples were segmented into 600-pL droplets in a microchannel with a cross section of W (100 mu m) x H (25 mu m), and the droplets were merged together. For acceleration of the mixing, the merged droplet was shuttled back and forth. Recirculation in a moving droplet was proven to be effective for high-speed mixing in this diffusion-dominated scale. All the handling operations were carried out using air pressure transferred through microfabricated vent valves which have been newly developed. The demonstrated strategy, including fabrication, leads to high-performance and low-cost micro total analysis systems (mu TAS).