Fig. 2: Positive training of double network agarose/PNIPAm hydrogel.

a The swelling ratio change in response to heating-cooling cycles, showing the increase in response by training above the threshold temperature. b Effect of agarose concentrations on the training and response ratios. c Effect of training temperature on the training and response ratios. Green arrows indicate a change in response ratio after training. Red dashed lines are to guide the eye. d Swelling ratio change of hydrogels undergoing training at different temperatures. e Stepwise training of the hydrogel. Insets show photographs and SEM images of the hydrogel before and after training. Scale bar: 10 mm (black) for the photograph and 1 µm (red) for SEM images. Error bars represent standard deviations of measurement from four samples. Training cycle consists of 5 min at HT and 30 min at RT.