Locally and Dynamically Controllable Surface Topography Through the Use of Particle-Enhanced Soft Composites

A new class of soft composite materials with dynamically tunable and reversible surface topographies is introduced that allows a wide diversity and local positioning of surface features. The particle-enhanced soft composites are comprised of a soft elastomeric matrix with relatively stiff particles embedded below the surface. Upon application of external stimuli, a surface that is originally smooth and flat (or of other initial topology) transforms to engineered surface topographies. Finite element based micromechanical simulations are used to design and study the hybrid material structures that govern the evolution in surface topographies. Physical prototypes are fabricated using multimaterial 3D-printing, and then experimentally evaluated to validate the accuracy of our simulations. It is demonstrated that a rich variety in periodic and random surface features including variable waves, crease-like features, flat apexes, and valleys can be attained by changing different dimensionless geometric parameters (e.g., relative particle size, shapes, spacing, and distributions). Furthermore, these surface features can be locally controlled by positioning of particles and do not rely on instabilities. The material design depends primarily on the geometry of the particles and the arrays, making this approach to on-demand custom and reversible surface patterning applicable over a wide range of size scales.