An integrated electrostatic peristaltic gas micropump with active microvalves.

Abstract

A high-performance micro gas pump for high-speed micro gas chromatography (muGC) as well as several microfabrication technologies used to build the proposed micropump, are reported. A high-flow, high-pressure, low-power, and small micro gas pump is needed for sample collection and transportation in a micromachined gas chromatography. Previous micro gas pumps have suffered from low flow-rate, low pressure, large volume, and high-power dissipation. The developed micropump utilizes a number of techniques to achieve low-power electrostatic pumping in a compact module: (1) a multi-stage configuration that creates a small pressure in individual stages, and accumulates these pressures to obtain a high pressure differential across the entire pump; (2) a fluidic resonance-based operation to achieve high flow rate despite the tiny volume displacement of each pump; (3) active timing control of microvalves to regulate pump operation; and (4) several new designs including checkerboard microvalves, dual curved electrodes, and dual pumping chambers. The micropump is fabricated by using new microfabrication technologies. First, a Parylene-assisted wafer bonding technology, performed at a low-temperature of &sim;230C&deg;, constructs enclosed pumping chambers without damaging polymer structures, and provides a bond strength of 3.6MPa. Second, a wafer-level Parylene membrane transfer technique constructs pumping and valve membranes between two pumping chambers. The membranes are thin (0.8mum-thick), flexible, freestanding, and cover a shallow (&sim;5mum deep) and wide (&sim;2000mum long) recess. Third, an electrode buckling technology forms a smooth out-of-plane curved electrode using only one mask by buckling the thin films under built-in stress with a uniformity of 95% across a 100mm wafer. The fabricated 18-stage pump operates at 14 kHz and produces an air flow rate of 4.0cc/min and a pressure of 17500Pa, using a total power of &sim;57mW. It has operated over a 6-month period for a total of &sim;300 minutes and has a volume of 25.1x19.1x1mm<super>3</super>. Four- and two-stage pumps demonstrated flow rates of 3.0 and 2.1cc/min and pressures of 7000 and 2500Pa. The 4-stage pump is combined with a microcolumn and a chemiresistor to form a functioning muGC where 4 vapors are separated within 7 seconds. This is the first MEMS-GC analysis featuring an integrated micropump.