Responsive Wrinkles

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Responsive Wrinkles
Wrinkling, 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).