Micro-pumps are very important for advanced micro fluidic systems such as Lab-on-a-Chips and micro cooling systems, which have been well investigated during the last decades. We developed a valve-less micro-pump with one diffuser/nozzle shaped channel and a variable volume chamber which produces an oscillating flow. One-way flow of the micro-pump was realized in an asymmetric channel by an oscillating flow. Micro-pumps require at least total pump head of 40 kPa to apply micro fluidic devices. In order to achieve above pump head, improvement of original pump is required. In this study, the effect of channel geometry on the pump head of a valve-less micro-pump with a diffuser/nozzle shaped channel was investigated. The micro-pump channels of various angles of 30, 60, 90 degrees between main channel and connecting channel to the chamber with actuator were prepared. The cross section dimensions of the micro-pump channel were 500 microns × 500 microns. The spread angle of the diffuser shape was 50 degrees. The measured pump heads were rearranged using dimensionless numbers as head coefficient to compare for various pump channels. As a result, larger head coefficient was obtained at the angle of 30 degrees which had higher junction loss from the chamber to the inlet channel. The maximum pump head 10.2 kPa was obtained by improved micro-pump, and the value was 1.5 times higher than original pump. The pump head for various drive conditions and channels were estimated using simplified analysis for unsteady operation of the pump based on Bernoulli’s theorem. The calculated pump characteristics agreed with the measured ones.

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