Figure 8.

4D printed artificial scale two-phase shape deformation (a) compared with two-phase passive-nastic movement of the Bhutan pine scale (b). Both scales are clamped at the basal region and undergo two successive bending deformations upon desiccation. The two separate sequences indicate a different image registration timescale, highly variable due to environmental conditions, and therefore, comparative image sets were created to match the deformation stages as opposed to the time. Starting fully wet (t = 0, image set A) both scales present notable transversal curvature with negligible longitudinal curvature. At the first actuation stage (image sets A–C), transversal curvature alone has markedly decreased. This first stage is then followed by a significant change in longitudinal curvature until a maximum bending angle is reached (image sets C–F). (Online version in colour.)