Abstract: A microdevice in the form of a microactuator or micropump. A microdevice for providing reciprocating motion at a high repetition rate, including a cell having an output wall with at least a portion movable, such as a diaphragm or inlet and outlet valves. A charge of gas in the cell and a source for cyclicly and directly heating the gas to increase the gas pressure in the cell and move the diaphragm or control the valves, the source for heating including a pulsed source for generating transient gas pressure increases in the cell at cycle times of not more than about 50 microseconds, with the cell including an arrangement for cooling the gas for reducing the gas pressure in the cell. In one embodiment, the source for heating includes a source of photons and an arrangement for directing the photons into the cell to the gas or to the cell inner surface.