Silicon linear actuator driven by electrochemomechanical strain of polypyrrole film

A silicon linear microactuator driven by the electrochemomechanical strain of polypyrrole was fabricated using silicon microfabrication processes and galvanostatic electropolymerization of a polypyrrole thin film using a methyl benzoate electrolyte solution containing tetra- n-butylammonium bis(trifluoromethansulfonyl)imide (TBATFSI). The fabricated actuator consisted of a silicon microspring on which a polypyrrole film was deposited. The microspring was 15 mm long, 0.5 mm wide, and 60 μm thick; the polypyrrole film was 15 mm long, 7 mm wide, and 91 μm thick. The actuator exhibited a contraction and expansion ratio of nearly 12% under a load of 0.2 N in an aqueous solution of an electrolyte, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), within the potential range from −1 to 1 V with a sweeping rate of 10 mV/s. This structure may be suitable for the actuation of small microelectromechanical system (MEMS) structures that require a large displacement with a large driving force under a low driving voltage range.