Microchip Coulter particle counter

This paper presents a micro device employing the Coulter principle for counting and sizing of living cells and particles in liquid suspension. The microchip Coulter particle counter (μCPC) has been employed in a planar silicon structure covered with glass, which enables detailed observation during operation. By sheathing of a nonconductive liquid on either side of an electrolyte, it is possible to optimize the sensitivity to a specific cell-size. A method for measuring the relative flow-rates between liquid phases with different conductivity is presented. The method utilizes the laminar flow and short contact time of liquids in microchannels. As a result, the width of the liquids can be controlled without knowing the actual flow rates. The μCPC has been fabricated by standard microfabrication techniques, including RIE, wet silicon etching, metalization and anodic bonding