Ichiroh Takeuchi

Expansion and contraction of polymer electrodes under applied voltage

The authors developed a scheme for characterizing the expansion and contraction of polymer electrodes when voltage is applied by coupling a symmetry analysis, the elasticity theory, and the experimental measurements. This scheme was applied to the bucky-gel electrodes and the expansion and contraction rates for the cathode and the anode were determined separately. For the case of the bucky-gel electrodes, it was found that the cathode expands and the anode contracts as voltage is applied. The stress exerted inside the electrode layers was also determined and the mechanical efficiency of the actuator composed of the bucky-gel electrodes is discussed.The authors developed a scheme for characterizing the expansion and contraction of polymer electrodes when voltage is applied by coupling a symmetry analysis, the elasticity theory, and the experimental measurements. This scheme was applied to the bucky-gel electrodes and the expansion and contraction rates for the cathode and the anode were determined separately. For the case of the bucky-gel electrodes, it was found that the cathode expands and the anode contracts as voltage is applied. The stress exerted inside the electrode layers was also determined and the mechanical efficiency of the actuator composed of the bucky-gel electrodes is discussed.

Li ion/vapor grown carbon fiber polymer actuators show higher performance than single-walled carbon nanotube polymer actuators

The effects of Li tetrafluoroborate (Li[BF4]) and lithium bis(trifluoromethanesulfonyl)imide (Li[TFSI]) salts on the electrochemical and electromechanical properties of an actuator using a poly(vinylidene fluoride-co-hexafluoropropylene)-supported vapor grown carbon fiber (VGCF)/ionic liquid (IL) gel electrode formed without ultrasonication were investigated. At a slow sweep rate of 1 mV s−1, the measured double-layer capacitance values for the VGCF/Li[X]/IL actuator were in the range of 20.0–42.3 F g−1, and were larger than that for an IL-only actuator. The capacitance was found to increase with the Li[BF4] content, but was independent of the Li[TFSI] content. All of the VGCF/Li[X]/IL actuators exhibited a larger amount of strain than IL-only actuators, and for a VGCF/Li[TFSI]/EMI[TFSI] actuator with a Li[TFSI]/EMI[TFSI] molar ratio of 1.0, the maximum strain was greater than that for an IL actuator containing single-walled carbon nanotubes. Moreover, the frequency dependence of the displacement response for the VGCF/Li[X]/IL actuators was successfully simulated using an electrochemical kinetic model, similar to the case for SWCNT and VGCF based actuators containing metal oxide. The results yielded the strain in the low-frequency limit in addition to the time constant of the response.

A mesoporous carbon polymer actuator with superior performance to that of single-walled carbon nanotube polymer actuators

The electrochemical and electromechanical properties of poly(vinylidene fluoride-co-hexafluoropropylene) actuators prepared using a nongraphitized mesoporous carbon black (MCB)–ionic liquid (IL) gel electrode formed without ultrasonication were compared with those of actuators prepared using carbon black (CB), multi-walled carbon nanotubes (MWCNTs) and single-walled carbon nanotubes (SWCNTs). The double-layer capacitances for the MCB/IL electrodes were larger than that for the CB/IL electrode. In particular, the double-layer capacitance for the MCB/EMI[BF4] electrode was larger than that for other MCB-based electrodes. Over a wide frequency range of 0.005–1.0 Hz, the strain produced by the MCB/EMI[BF4] actuator was larger than that of the other MCB-based actuators. This suggests that there is a relationship between the pore size in the MCB and the IL anion size. The maximum strain value for the MCB/EMI[BF4] actuator was larger than that for the non-MCB-based actuators, and in particular, was about 1.5 times larger than that for the SWCNT-based actuators. Thus, an MCB-based actuator formed without ultrasonication exhibited a performance that surpassed those of the CB- and SWCNT-based actuators. Consequently, it could generate sufficient strain for real-world applications without the need for specialized SWCNTs.