Physical Sciences

Honorable Mention: Andre Paredes and Wei Xu, University of California, Irvine
Polymer Based Micro Flow Regulator

Lab-on-a-chip is a growing technology that incorporates microfluidics. Microfluidics can be controlled and regulated through microvalves and microflow regulators. Currently very little polymer based microvalves exist.This paper presents a functional polymer, polydimethylsiloxane or PDMS, based microflow regulator that can readily be applied and transformed into a microvalve. The device integrates "air cavities" protruding outward from the sides of the microchannel to establish the flow regulator and valve. Due to the polymer's hydrophobic properties, the "air cavities" are created as liquid travels down the microchannel. Upstream from the "air cavities," a thermal gradient is applied to evaporate liquid as it passes by, creating air within the microchannel. A segment of reduced width channel immediately following the "air cavities" increases flow resistance and forces air to condense into the "air cavities." The thermal gradient dictates the air concentration, and the air concentration dictates the fluidic flow. Thus, correct manipulation of the thermal gradient can result in regulation of microflow down the microchannels, functioning as a microflow regulator. In addition, with a specific thermal gradient the air can be manipulated to build up, until a bubble blockade is formed, functioning as a microvalve. Our experiment, therefore, shows a simple and cheap device that forms a functioning microflow regulator that can readily be transformed into a microvalve.