**3.2 Experimental procedure**

The polymerization of PPy films was carried out using a computer-controlled potentiogalvanostat (Hokuto Denko HZ-5000). A counter electrode (Ti), a reference electrode (Ag/AgCl), and a working electrode (Ti) were immersed into methyl benzoate solutions of 0.25 M pyrrole and 0.2 M N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethanesulfonyl)imide, and the potential voltage was controlled to keep a constant current of 0.2 mAcm-2 for 4 h at 20 oC between the counter electrode and the working electrode. The thickness of the PPy films was measured to be approximately 150 m using a micrometer. The obtained films were peeled off from the electrode, rinsed with acetone, and dried in air. The PPy films were cut into 20 x 5 mm2 strips to form the PPy actuators.

The actuator characterization system that utilizes a balance to measure the expansion and contraction ratios under load stress was described in Fig. 2.4. (Morita et al., 2010, Chida et al., 2010). The PPy actuator was used as the working electrode in the 1 M LiTFSI aqueous electrolyte solutions containing 2-propanol at various concentrations of 0, 20, 30, 40, 60, 80, and 100%. Both of the PPy actuator ends were clipped with two metal plates. The PPy actuator exhibited the expansion and contraction motions under the alternating potential with the triangular wave shape applied between the PPy actuator and the counter electrode. The potential voltage difference between the PPy actuator and the electrolyte solution was monitored using the Ag/AgCl reference electrode. The peak values of the potential voltage

to decrease within the voltage swing (-1 V to + 1 V) for 15 cycles. Thus, it may possible to conclude that the corrugated PPy actuator have better performances than those of the plane

**3. Effect of 2-propanol concentration in electrolyte solution on polypyrrole** 

Recently, it has been reported that some PPy actuators exhibit strains of more than 10%, and that some of those even achieved strains of up to 40% (Hara et al., 2004). The improved strain has been mostly achieved using an electrolyte of tetra-n-butylammonium bis(trifluoromethansulfonyl)imide (TBATFSI) during PPy electropolymerization. These

Hara et al. reported that their TFSI-doped porous PPy films exhibited increased deformation when their aqueous lithium bis(trifluoromethansulfonyl)imide (LiTFSI) electrolyte solutions contained propylene carbonate (Hara et al., 2004). They attributed those effects to the swelling of the PPy film caused by the penetration of propylene carbonate. The swelled PPy film could more easily pass TFSI anions. We also immersed TFSI-doped PPy films into several organic chemicals, and found that the PPy films showed notable swelling in 2 propanol (Hoshino et al., 2011). Therefore, it was interesting to investigate whether the PPy actuators show improved deformation behaviors in aqueous LiTFSI solutions containing 2 propanol. In this section, the electrochemical deformation characteristics of TFSI-doped PPy soft actuators in aqueous LiTFSI solutions with different 2-propanol concentrations are

The polymerization of PPy films was carried out using a computer-controlled potentiogalvanostat (Hokuto Denko HZ-5000). A counter electrode (Ti), a reference electrode (Ag/AgCl), and a working electrode (Ti) were immersed into methyl benzoate solutions of 0.25 M pyrrole and 0.2 M N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethanesulfonyl)imide, and the potential voltage was controlled to keep a constant current of 0.2 mAcm-2 for 4 h at 20 oC between the counter electrode and the working electrode. The thickness of the PPy films was measured to be approximately 150 m using a micrometer. The obtained films were peeled off from the electrode, rinsed with acetone, and dried in air. The PPy films were cut into 20 x 5 mm2 strips to form the PPy

The actuator characterization system that utilizes a balance to measure the expansion and contraction ratios under load stress was described in Fig. 2.4. (Morita et al., 2010, Chida et al., 2010). The PPy actuator was used as the working electrode in the 1 M LiTFSI aqueous electrolyte solutions containing 2-propanol at various concentrations of 0, 20, 30, 40, 60, 80, and 100%. Both of the PPy actuator ends were clipped with two metal plates. The PPy actuator exhibited the expansion and contraction motions under the alternating potential with the triangular wave shape applied between the PPy actuator and the counter electrode. The potential voltage difference between the PPy actuator and the electrolyte solution was monitored using the Ag/AgCl reference electrode. The peak values of the potential voltage

actuators generally function under a low potential voltage range less than 1 V.

PPy actuator.

**3.1 Introduction** 

reported.

actuators.

**3.2 Experimental procedure** 

**actuator performance** 

were -1 and +1 V, and the potential sweep rate was 10 mVs-1. The extension and contraction of the PPy actuator was measured by monitoring the displacement of the weight position using a laser displacement sensor (Keyence LE-4000). Moreover, a load stress of 0.3 MPa was applied on the PPy actuator by placing corresponding weights on the saucer of the balance.
