Tunable surface morphology via patterned cavities in soft materials

There is a rich diversity of surface topologies controllably engineered by patterning cavities embedded beneath the surface of soft materials. Upon external compression, the surface undergoes the reversible transformation from the flat surface to various surface topographies, including a periodic checkerboard pattern with alternate convex and concave features. To design the surface features, both two- (2D) and three-dimensional (3D) finite element based simulations are performed. It is demonstrated that the periodic surface features with controllable morphology, such as one-dimensional waves, checkerboard pattern, and mutually perpendicular apexes, etc., can be realized through varying cavity geometries (e.g., relative intercavity distance, shapes, and biaxial or uniaxial load). Additionally, a simple model for plate buckling is used to elucidate the effect of cavity aspect ratio on the surface pattern. Based on 3D printed prototypes, we further conduct experiments to validate the simulation results of 2D morphologies. The patterned cavities in soft materials make designing a variety of reversible surface features possible, offering an effective fabrication approach for wide application across multiple scales.