An electrostatic microactuator system for application in high-speed jets

The development of an electrostatic microactuator system for the study and control of high-speed jet flows is presented. The electrostatic actuator is 1.3 mm wide, 14 mum thick and has a head that overhangs a glass substrate, intruding into the flow by 200 mum. The actuator has been fabricated using a bulk-silicon dissolved-wafer process to increase device thickness for increased stiffness in the flow direction. Characterization of the new actuators demonstrated their ability to oscillate with amplitudes of up to 70 mum peak-to-peak at resonant frequencies of 5 and 14 kHz. This is a very large motion at such high frequencies when compared to existing macro or micro mechanical actuators. The full actuator system was mounted around the exit of a high-speed jet using several sector-shaped PC boards. This enabled detailed examination of the ability of the actuators to withstand the flow environment and generate substantial flow disturbances. The results showed that the micro actuators functioned properly up to jet speeds of 300 m/s while generating disturbances in the shear layer surrounding the jet comparable to those produced by other macro-scale methodologies.