Piezoelectric transformers for the production of low-voltage atmospheric-pressure gas discharges and electrohydrodynamic flows

Typically, atmospheric-pressure gas discharges are formed by the application of very high voltages, $\sim$ kV, to metal electrodes. However, for some applications, including hand-held devices, such voltages can be prohibitive from a design perspective. In this work, we explore using a piezoelectric transformer to amplify a relatively small voltage input ($\sim$ 10 V) to a sufficiently high potential to breakdown air. Analogous to classical magnetic transformers which convert between magnetic and electrical energy to produce a gain in voltage, piezoelectric transformers use the electromechanical coupling present within the piezoelectric to produce a similar voltage gain. As such, a high potential can be formed on the surface of a piezoelectric crystal that is sufficient to form a corona-like discharge. In this work, we demonstrate the generation of atmospheric air discharges off of the surface of piezoelectric transformers with input voltages as low as 7 Vamp. We use two different configurations, one with the piezoelectric surface acting as an electrode in a traditional two-electrode corona discharge configuration and the second using no second electrode to form a surface discharge. One potential application of these piezoelectric-driven discharges is as electrohydrodynamic flow sources, also called ionic wind generators. Using a combination of infrared thermography and anemometry, we measure the induced flows by piezoelectric-driven discharges, and explore how the external system and resonant frequency affect flow generation.