Figure 2.

The 4D functional model of the bi-axial curvature deformation. An initial set of 3D printed scales using differentiated bilayer regions composed of a constraint layer of oriented TPU and an oriented hygroscopic layer of WPC. (a) Fully wet 4D printed samples show different double curvature deformations in response to localized bilayer structure. (b) Localized WPC raster pattern regions in relation to global shape of scale. (c) The direction of hygroscopically induced expansion on WPC layer shown in relation to dominant axis of oriented TPU constraint. (Online version in colour.)