Wax micro actuator with semiconductor heating element

摘要

An actuator comprises a cavity 2 containing a working medium (wax) 3 that reversibly expands as it undergoes a phase change from a solid to a liquid state, a diaphragm 4 closing the cavity such that expansion and contraction of the wax causes the diaphragm to deflect. The heater is a semiconductor element such as a diode 6 disposed in the cavity. The actuator may be used in a pump for a medical infusion system (figure 6). The diode 6 and its connecting leads 7 may be positioned close to the diaphragm 4 to provide rapid, controlled response, and so that not all of the wax 3 is melted.