Thermal-expansion-type microactuator using paraffin as expansive material (Basic performance of a prototype linear actuator)

Our aim is to develop a microactuator to be used for endoscopic surgery. The purpose of this study was to construct cylinder-piston-type microactuators that are actuated by thermal expansion of paraffin. We use a paraffin as the material for expansion because paraffin has a large coefficient of expansion in the temperature range of 35 to 45 degrees of centigrade. For smooth actuation of the piston, we must prevent the paraffin from sticking on to the inside surface of the cylinder. Thus the paraffin is enclosed in a silastic tube. The cavity between the cylinder and the tube is filled with silicone oil for lubrication and prevention of expansion loss. The outer diameter of the actuator is 2.5 mm and its length is 130 mm. The actuator can generate a stroke of 8 mm against a load of 1 kg.