Responsive wrinkles

Responsive wrinklesWrinkling, buckling, and creasing phenomena in synthetic and natural materials represents an opportunity to guide the placement of nanostructures that enhance the optical, mechanical, and/or electronic properties of materials.  Working in the Materials Research Science and Engineering Center on Polymers at UMass Amherst, Crosby discovered that reversible wrinkling can guide colloidal and nanoparticle assembly into well-ordered patterns across macroscopic length scales. Due to the sinusoidal shape of top-constrained, swelling-induced wrinkling, the deposition of fluorescent polystyrene (PS) colloids  occurs selectively in the wrinkle patterns during solvent evaporation. After complete evaporation of solvent, these colloidal assemblies are embossed as the surface snaps back to the smooth state (top schematic).  A key advantage of this process is the ability to tune the assembly pattern by the solubility of the dispersing solvent in the wrinkled substrate.  Solvent choice controls the applied strain that causes wrinkling, and the extent of strain beyond the critical value dictates the specific morphology obtained (bottom schematic).