A Thermal-Expansion-Type Microactuator with Paraffin as the Expansive Material : Basic Performance of a Prototype Linear Actuator

Abstract

Our aim is to develop a microactuator for use in endoscopic-surgery. The purpose of this study was to construct cylinder-piston-type microactuators actuated by thermal expansion of paraffin. We use paraffin as the material for expansion because paraffin has a large coefficient of expansion in the temperature range of 35 to 45 degrees centigrade. For smooth actuation of the piston, we must prevent the paraffin from sticking 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 8mm against a load of 1 kg.