**2.2.1 Fabrication processes of PPy soft actuator**

The PPy thin film was fabricated by electropolymerization. The electropolymerization of PPy was done in a methyl benzoate solution with a volume of 50 ml in which pyrrole monomers with a concentration of 0.25 mol dm-3 and the electrolyte (N, N- Diethyl- Nmethyl-N-(2-methoxyethyl) ammonium bis (trifluoromethanesulfonyl) imide with a concentration of 0.2 mol dm-3 are dissolved.

The working electrode was a Au thin film sputtered on an acrylic board and the counter electrode was a Ti plate. The area of the electrodes immersed in the solvent was 30×25 mm2. The polymerization was done at a constant current of 0.2 mA cm-2 for 4 hrs at the room temperature. The PPy thin film was polymerized with the doped anions in the supporting

Polypyrrole Soft Actuators 165

Figure 2.3a. and 2.3b. show the scanning electron microscope (SEM) images for the PPy films formed on the corrugated working electrode and the plane working electrode, respectively. The surfaces of the both PPy films look like a sponge surface. However, no

notable differences were observed between the two films.

(a) (b)

**2.2.2 Characterization of PPy soft actuator** 

Working electrode

contraction ratio of PPy actuators.

Fig. 2.3. Scanning electron microscope images of the PPy surfaces formed on the corrugated working electrode (a), and the PPy surface formed on the plane working electrode (b).

Figure 2.4. shows the actuator characterization system which utilizes a balance to measure the expansion and contraction ratios. The PPy actuator was used as a working electrode in the LiTFSI solution of 1 mol dm-3, and the both of PPy actuator edges were suspended by

Counter electrode

Laser displacement sensor

Polypyrrole Weight

Fig. 2.4. Conceptual description of experimental setup for measuring the expansion and

electrolyte. The PPy thin film was then peeled off from the electrode, and it was used as an actuator.

A working electrode with a corrugated structure and a plane structure were used for fabricating PPy thin film having the corrugated structure and the plane structure. Figure 2.1. describes the process to fabricate the corrugated PPy actuator. The corrugated working electrode was made by the following methods. Firstly, an acrylic board was processed to form a corrugated structure which had the ditches of 1 mm in depth, and spacing between the ditches was 5 mm as seen in Fig. 2.1. Next, the Au thin film was coated on the processed surface of the acrylic board by sputter deposition. PPy was polymerized on the acrylic board covered by the Au thin film which worked as a working electrode. Then, the corrugated PPy thin film was peeled off from the electrode by dissolving the acrylic board in acetone. The PPy thin film was cut into slices with the width of 6 mm, and these were used as actuators. PPy films without the corrugated structure were also fabricated on the plane acrylic board with the Au film for comparison. The thicknesses of the PPy films were measured using a micrometer, and these are approximately 14.5 m for both of the corrugated PPy film and the plane PPy film.

Fig. 2.1. Conceptual description of the corrugated PPy actuator fabrication process.

Fig. 2.2. Optical microscope image of the surface of the corrugated acrylic board.

electrolyte. The PPy thin film was then peeled off from the electrode, and it was used as an

A working electrode with a corrugated structure and a plane structure were used for fabricating PPy thin film having the corrugated structure and the plane structure. Figure 2.1. describes the process to fabricate the corrugated PPy actuator. The corrugated working electrode was made by the following methods. Firstly, an acrylic board was processed to form a corrugated structure which had the ditches of 1 mm in depth, and spacing between the ditches was 5 mm as seen in Fig. 2.1. Next, the Au thin film was coated on the processed surface of the acrylic board by sputter deposition. PPy was polymerized on the acrylic board covered by the Au thin film which worked as a working electrode. Then, the corrugated PPy thin film was peeled off from the electrode by dissolving the acrylic board in acetone. The PPy thin film was cut into slices with the width of 6 mm, and these were used as actuators. PPy films without the corrugated structure were also fabricated on the plane acrylic board with the Au film for comparison. The thicknesses of the PPy films were measured using a micrometer, and these are approximately 14.5 m for both of the corrugated PPy film and

Acrylic board

Au film

PPy

Fig. 2.1. Conceptual description of the corrugated PPy actuator fabrication process.

Fig. 2.2. Optical microscope image of the surface of the corrugated acrylic board.

PPy actuator

actuator.

the plane PPy film.

Figure 2.3a. and 2.3b. show the scanning electron microscope (SEM) images for the PPy films formed on the corrugated working electrode and the plane working electrode, respectively. The surfaces of the both PPy films look like a sponge surface. However, no notable differences were observed between the two films.

Fig. 2.3. Scanning electron microscope images of the PPy surfaces formed on the corrugated working electrode (a), and the PPy surface formed on the plane working electrode (b).
