Explosive micro-bubble actuator

Explosive evaporation occurs when a liquid is exposed to extremely high heat-fluxes. Within a few microseconds a bubble in the form vapour film is generated, followed by rapid growth due to the pressure impulse and finally the bubbles collapse. This effect, which already has proven its use in current inkjet printer technology, can be used to produce mechanical work. Here it will be utilised to deflect a 1 μm thick low-stress silicon-nitride membrane. Bubble nucleation and growth are studied with stroboscopic microscopy and membrane deflection is measured with a laservibrometer. Within a few microseconds the bubbles can produce a pressure of several bar resulting in a membrane deflection of micrometers and a membrane speed of more than 1 m/s.