Electrostatically Driven Airborne Ultrasound Transducer with Perforated Backplate for Nonlinear Acoustic Applications
* Presenting author
We propose a thin transducer driven by an electrostatic force (ESF) for a high-intensity airborne ultrasound. A prototype transducer with 334µm-thickness emitted 392Pa (RMS) on the surface when driving at 51kHz. This value is large enough to apply for nonlinear acoustic applications. A generation of high-intensity ultrasound needs a several μm displacement of a diaphragm. Conventional ESF-driven parallel-plate transducers have not achieved it because a thin air layer between electrodes prevents the diaphragm from vibrating.We solved the problem by providing perforations at a backplate electrode. The air between the diaphragm and the perforated backplate can travel freely through the perforations when the diaphragm vibrates. In addition, we drove the transducer by controlling the amount of electrical charge accumulated in the diaphragm. This driving method can prevent a pull-in phenomenon. In the experiment, the diaphragm vibrated with an average amplitude of 3μm (RMS) at 51kHz.Our transducer can be fabricated by laminating flexible materials and can be formed in a sheet-shaped phased array device. Thus, our transducer can be an alternative to the piezoceramic transducers applied for the nonlinear applications.