Bubble inclusion and removal using PDMS membrane-based gas permeation for applications in pumping, valving and mixing in microfluidic devices

Abstract

Several advancements in fluid handling applications of a gas-permeable polydimethylsiloxane (PDMS) membrane are demonstrated. Devices for controlled pumping, bubble injection, bubble removal and mixing are demonstrated using a three-layered fabrication method. The ability of a gas-permeable membrane to control flow in glass channels is determined. Consistent flow rates ranging from approximately 1 to 14 µl min−1 were observed using control pressures from 100 to 700 mbar. Bubble injection and removal from microfluidic channels was performed in monolithic PDMS devices using several bubble trap geometries at fluid flow rates over 100 µl min−1. The rate of removal of the air in the bubble trap was determined as a function of the area of membrane exposed and the applied vacuum. The PDMS membrane was shown to be an effective tool for the injection and removal of air bubbles in a method of enhancing mixing using bubbles and branched microchannels. The amount of mixing was optically determined before and after bubbles entered the fluid channel. The ability to produce all of these compatible components using a single fabrication process is a step toward inexpensive, parallel, highly integrated microfluidic systems with minimal external controls.