Investigation of sheath flow chambers for flow cytometers - (Micro machined flow chamber with low pressure loss)

A new type of sheath flow chamber with low pressure loss was developed using micro-machining. The chamber was formed by laminating three 100-mu m-thick, photo-etched, metal plates. The device uses sheath-flow geometry : particles in suspension, which enter the chamber via an axial specimen nozzle, are enveloped by a buffering sheath flow and transported to a square capillary tube with cross-section of 300 mu m x 300 mu m. Finite element viscous-flow analysis is used to examine the flow behavior in the quasi-two-dimensional passage configuration which produces the fluid-dynamic focusing flow. Experimental measurement showed a smooth constricted sheath flow, and pressure loss was reduced to one-tenth of that which occurs with conventional glass flow chambers.