a miniature flow controller housing a fluid inlet and a fluid outlet , with the inlet pressure exceeding the outlet pressure . the outlet has orifices defined in a crystalline silicon membrane , along crystal planes of the silicon so that the geometry of the orifices is precisely known . the inlet and outlet are throttled by poppets which can seal the orifices on command of a device controller . the poppets are driven by shape retentive membranes which have two states , an open state and a closed state with a state change caused by application of small amounts of current to a resistive element in contact with the membrane . rapid actuation of the poppets causes operation of the valve in a pulse mode . where the fluid is a gas , pressure and temperature transducers measure conditions inside of the housing for application of gas law principles . by recording instantaneous pressure and temperature in the chamber , as the poppets are actuated , mass flow through the outlet orifices of the chamber is computed .