Elastic contact induced self-organized patterning of hydrogel films

When a flat rigid stamp contacts the surface of a soft hydrogel film, a competition between the adhesive and elastic forces engenders an isotropic, labyrinth pattern on the length scale of similar to 3H, where H is the film thickness, We present here a very simple, self-organized technique for aligning and modulating these patterns by using a patterned stamp and by changing the film thickness and the stamp-film intersurface distance. Many complex structures such as an array of femtoliter beakers and doubly periodic channels are generated from a simple stamp. The elastic nature of the patterns allows in-situ tuning, manipulation, and reconfiguration of structures. The patterns can also be made permanent by drying of the hydrogel.