An energy-saving method of heating for a chemomechanical poly(N-isopropylacrylamide) gel with Jouleʹs heat

Macroporous poly(N-isopropylacrylamide) gel, swollen in NaCl solution, showed electric conductivity inside the gel. Swollen gel could be heated electrically by the application of AC voltage (100 V, 50 Hz) through the inserted electrodes within both ends of the gel rod. Jouleʹs heat generated inside the gel was effective in bringing about a phase transition of gel. The gel swollen in 0.5 M NaCl solution at 22°C could generate the contractile stress with increasing temperature of gel after applying AC voltage. The deswelling rate and the maximum stress generated were 1.3 kPa s−1 and 8.0 kPa, respectively. The device of a bundle of 5 gel rods ( = 1.5 mm) could lift the weight (10 kPa as tensile strength) within 20 s, and work mechanically faster than the device of magnetic heating reported in our previous paper. The electric heating device gel could save more energy by reducing heat loss due to radiation.