Fig. 4: Soft robots based on hybrid polymer-crystal materials.

a Crystals of P²//2,3 straighten when they are placed on a bare palm and bend when they are placed on a nitrile glove due to response to the variation in humidity. b A model “inflorescence” made of PDDA/PSS//2 and crystal 3. c An artificial model “inflorescence” of rain lily (Z. grandiflora) prepared from P²//2 and crystal 3. d A model of a plant tendril made of P²//3 which can curl by a change in temperature (Supplementary Movie 3). e, f Schematic diagram (e) and photographs (f) of a soft robot capable of performing a spider-like motion (Supplementary Movie 4). g, h Schematic diagram (g) and photographs (h) of a soft gripper made of P²//1 (Supplementary Movie 5). i Schematic representation of the mechanism of ‘walking’ of organic polymer-crystal hybrid materials across a surface induced by periodic changes in aerial humidity. j Snapshots of the ‘walking’ of a hybrid crystal of P²//3 (Supplementary Movie 6).