A micro-sheath flow chamber for a particle analyzer was developed using micro-machining. Sheath flow geometry is formed in a two-dimensional passage configuration. A viscous flow analysis using the finite element method helps to examine the inside flow of a small passage and design the passage configuration. The micro-sheath flow chamber consists of bent passages for sheath fluid, a constricted passage, and a capillary tube. The height of these passages is 300 mu m. The viscous flow analysis reveals that swirl flow is generated at the constricted passage, causing the sample flow to scatter. This result suggests that a sample flow guide plate is needed to eliminate the swirl flow and induce a flow to envelope the sample fluid. Experimental measurement of the sample flow using a guide plate shows that smooth constricted sheath flow is obtained and that the velocity reaches 3.0 m/s, nearly the same speed as the value obtained by the viscous analysis.
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