Explosive Micro-Bubble Actuator

Explosive evaporation occurs when a thin layer of liquid reaches a very high temperature in a very short time. At these temperatures homogeneous nucleation takes place. The nucleated bubbles almost instantly coalesce forming a vapour film 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. In this case it will be utilised to deflect a 250 x 250 mum square and 1 mum thick low-stress silicon-nitride membrane. Within a few microseconds it can produce a pressure of several bar resulting in a membrane deflection of micrometers and a membrane speed of more than lm/s.