High-speed air microjet arrays produced using acoustic streaming for micro propulsion

This paper reports a new generation of micro air jet arrays, consisting of electrostatic micro actuators generating high-speed micro air jets using acoustic streaming for eventual application in chip cooling, gas pumping, and propulsion of micro-platforms. The microjet array is developed using a simple fabrication process and assembly method. The array contains 24 actuators with a volume of 0.9 × 0.9 × 0.1 cm³ and weighs 0.09g including wires and mounts. Several improvements have been achieved in this generation of devices, including: (1) light weight (smaller by >5×), (2) large diaphragm displacement (~10 μm), and (3) high operating frequency (~100 kHz). A 3.5× improvement in thrust-per-weight ratio is obtained with an average thrust of 0.75 μN per actuator. Diaphragm velocity is measured using a laser vibrometer and a peak jet speed of 7 m/s through the exit throat holes is estimated.