Abstract
This paper presents a power-free, self-contained microfluidic device in which a number of nanoliter-sized droplets can be parallelly and accurately metered and mixed for high-throughput analysis and/or portable systems. In this system, the absorption of air by pre-degassed PDMS and the change of capillary force due to sudden narrowing of the channel cross-section provide the mechanism for actuating, metering and mixing the flow of fluid in the microfluidic channels and chambers. With an array of channels and capillary valves combined with an array of pre-degassed PDMS pump chambers, the device can perform multiple liquid dispensing and mixing in parallel, and its performance and reproducibility are also evaluated. As a practical application, the proposed device is used to screen crystallization conditions of lysozyme. This device needs neither external power nor complex instruments for fluid handling. Thus, it offers an easy-to-use, inexpensive and power-free way to perform multiple nanoliter-volume distinct reactions in parallel format and should be ideally suitable for individual laboratories for various applications such as enzyme assay, protein crystallization, drug discovery, and combinatorial chemistry.