A fast and strong microactuator powered by internal combustion of hydrogen and oxygen

The development of fast and strong microactuators that can be integrated in microdevices is an essential challenge due to a lack of appropriate driving principles. In this paper, a membrane actuator powered by internal combustion of hydrogen and oxygen in a chamber with a volume of 3.1 nanoliters is demonstrated. The combustion in such a small volume is possible only for an extremely high surface-to-volume (S/V) ratio on the order of 10^7 1/m. The fuel with this S/V is prepared electrochemically in a special regime that produces only nanobubbles. A cloud of nanobubbles merges, forming a microbubble, which explodes, increasing the volume 500 times in 10us. The actuator generates an instantaneous force up to 0.5N and is able to move a body 11,000 times more massive than itself. The natural response time of about 10ms is defined by the incubation time needed to produce an exploding bubble. The device demonstrates reliable cyclic actuation at a frequency of 1Hz restricted by the effect of electrolyte aging. After 40,000 explosions, no significant wear in the chamber is observed. Due to record-breaking acceleration and standard microfabrication techniques, the actuator can be used as a universal engine for various microdevices including micro-electro-mechanical systems, microfluidics, microrobotics, wearable and implantable devices.