Low-power electrostatic microthruster for propulsion based on helmholtz-resonance

This paper reports the development of a low-power electrostatic microthruster based-on Helmholtz resonance. This fluidic resonance phenomenon is utilized to create high-speed jets of air for thrust generation. The microthruster contains a curved-electrode (~8.8 mum deep) and provides high force to, and large deflection of a vibrating membrane thus resulting in twice higher thrust performance than previously reported devices with a flat-electrode design. The out-of-plane curved electrode is formed on a silicon wafer through the controlled buckling of stressed thin films of oxide, poly silicon, and nitride. The fabricated device contains 25 microthrusters, has a footprint of 1.6 times1.6 times 0.1 cm³ , and weighs about 0.35 g. It operates using a 140 V and 70 kHz sinusoidal signal and produces: 1) thrust of 55.6 muN, 2) maximum air velocity of 1.2 m/s, and 3) average velocity of 1.0 m/s across the whole chip. The average power consumption of the 25 micro thruster array is 3.1 mW. The generated jet was visualized by pumping ethanol clouds into a vertical gas stream up to 12 cm.