Fig. 4. Physical experiments with 4 × 4 Kilobot Soft Robots that are programmed to move forward, first in a square lattice shape, then in a compressed shape, and finally relaxing to restore their original shape.

a Bird’s-eye view of the experimental area, generated by superimposing snapshots taken from a typical experimental trial. The vertical dotted lines represent the positions where shrinking and expanding procedures are externally triggered, respectively. b Distortion, measured as the root-mean-square deviation of all internal angles from 90° for each of the 11 trials. The reference value is shown as a grey dotted line: the deviation is 0° for the first 60 cm (square lattice), 50° from 60 cm to 140 cm (stretched lattice), and again 0° thereafter. The black dashed line represents the mean value.