**5.5 Conclusion**

Two kinds of PPy thin film actuators with or without the silicon MEMS microspring were fabricated and compared. The polypyrrole thin films with the thickness of 91 m were deposited by galvanostatic electropolymerization of a polypyrrole thin film using a methyl benzoate electrolyte solution of tetra-n-butylammonium bis(trifluoromethansulfonyl)imide (TBATFSI). One of the actuators was inserted with the silicon MEMS microspring with the length of 15 mm, the width of 0.5 mm, and the thickness of 60 m. The MEMS PPy actuator exhibited nearly 12% of the electrochemical strain under the load of 0.2 N in a water solution of an electrolyte, lithium bis-trifluoromethane sulphonyl imide (LiTFSI) at the bias sweep rate of 10 mVs-1 in the voltage range between –1 and 1V. The load stress was approximately 0.3 MPa. Although the performances of the MEMS actuators showed some degradation compared to the PPy actuator without the MEMS microspring, the MEMS PPy actuator may be beneficial to drive MEMS structures, which require a large strain and a large stress with a low voltage actuation.
