Research paperInvestigation of a multistage micro gas compressor cascaded in series for increase pressure rise

•Multistage micro gas compressor gas pump is investigated to generate more pressure rise.•Maximum pressure rise is generated at the diaphragm resonance frequency.•2-stage microcompressor generated twice the pressure rise to a single stage.•Each stage is tuned independently to its resonance to achieve maximum pressure rise.

This paper discusses the fabrication, assembly, and testing of a single-stage and a two-stage micro gas compressor cascaded in series to demonstrate the effectiveness of a multistage serial configuration with the utilization of piezoelectric unimorph diaphragms and passive microvalves. Gas compression is enabled with the large stroke volume from the diaphragm resonance frequency of ∼4.5-5.8 kHz, generating pressure rise for the single and multistage microcompressors. The microcompressors consist of passive micro check valves fabricated with SU-8 using MEMS microfabrication method and a piezo disc integrated to the CNC micromachined housings. The microcompressor pressure-flow performance curves and its performance based on the dependent parameters such as the voltage and the drive frequency are presented in this paper. The single-stage and the two-stage microcompressors operate at a low max voltage of 60 Vpp and at the resonance of the piezo diaphragm to achieve maximum pressure rise. From experimental result, maximum pressure rise of 10 kPa and a maximum flow rate of 32 standard cubic cm per min (sccm) were achieved from the single-stage device. The two-stage microcompressor showed improvement over the single-stage by generating a maximum pressure rise of 18 kPa and maintained the same maximum flow rate of 32 sccm. This was achieved with each stage operating independently at the diaphragm resonance. Additionally, we provided test results of the microvalve pressure-flow curve and test characterization of the unimorph piezo disc.