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A micromixer using direct ultrasonic vibration is first reported in this paper. The ultrasonic vibration was induced by a bulk lead‐zirconate‐titanate (PZT; 5 × 4 × 0.2 mm), which was excited by a 48 kHz square wave at 150 V (peak‐to‐peak). Liquids were mixed in a chamber (6 × 6 × 0.06 mm) with an oscillating diaphragm driven by the PZT. The oscillating diaphragm was in the size of 6 × 6 × 0.15 mm. Ethanol and water were used to test the mixing effectiveness. The laminar flows of ethanol (115 μL/min) and water (100 μL/min) were mixed effectively when the PZT was excited. The entire process was recorded using a video camera.

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Disruption of microbial cells by pressurized carbon dioxide at both subcritical and supercritical temperatures has been previously investigated. This method differs in principle from other disruption techniques and was found to have potential applications for rupture of a variety of microorganisms. However, it is not as effective for some of the microbial cells, including yeast, of which the cell walls are extremely robust and rigid. This work suggests an alternative operation to improve the disruption rates of cells by repeatedly releasing the applied fluid pressure within the cells in the midst of a disruption process. The improvement is substantial at all the experimental conditions studied.

No abstract