Microelectroforming and evaluation of honeycomb-groove nozzle plates of piezoelectric actuators for microspray generation

Abstract. Microspray generation by microfluidic nozzles comprising piezoelectric actuators featuring honeycombed grooves for antistiction was investigated. Microfluidic nozzles with 15-μm diameter were fabricated by the electroforming of nickel (Ni) with an estimated total deposition thickness of 40  μm. These nozzles were formed on the Ni plate in arrays of 31, 61, and 151; all nozzles were surrounded by a network array of honeycombed grooves with a line width of 30  μm. The piezoelectric actuators were bonded to the nozzle plates and filled with water to generate microsprays. The actuators were driven at electrical voltages of 40 to 142 V at 94 to 103 kHz, in which spray jets with volumetric rates of 4 to 65  ml/h were simply achieved and analyzed, agreeing with the proposed theory in the study. The use of particle image velocimetry (1500 fps) revealed that the turbulent flow of droplets from the sprays created strong recirculating vortices for a short time (0 to 12 ms). In addition, we experimentally demonstrated turbulence of droplets created at an average speed of 2.9±0.3  m/s, illustrating instable vortex-like motion. Hence the influence of turbulence on a variety of applications such as printing and cooling should be further concerned and investigated in the future.

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