Self-assembly of complex patterns by controlled mechanical instability in patterned polymer films

PMSE 151

Shu Yang, shuyang@seas.upenn.edu, Department of Materials Science and Engineering, University of Pennsylvania, 3231 Walnut Street, Philadelphia, PA 19104
Complex patterns play important roles in many technological applications. However, control of pattern formation and uniformity through self-assembly remains challenging. Much of the difficulty has been attributed to the instability at surface and interface on the pathway toward the thermodynamic equilibrium. Recently, there has been increasing interest to harness such instability to fabricate complex structures that are not possible by conventional methods. Here, I will discuss several approaches of manipulating the elastic instability in patterned polymer films. The combination of top-down process and bottom-up assembly offers an attractive way to maneuver the pattern formation in a controlled fashion, allowing us to create highly ordered herringbone wrinkles, superstructures of collapsed hydrogel pillars, and complex patterns of colloidal nanoparticles. In each example, we compare the experiments and theoretical modeling to elucidate the mechanism of pattern formation.