Fabrication of anisotropic and hierarchical undulations by benchtop surface wrinkling

This paper reports an electrical discharge assisted surface wrinkling process to produce hierarchical and anisotropic surface patterns on polymethylsiloxane (PDMS). Highly ordered sinusoidal wrinkles with tailored height (h) and wavelength (λ) are fabricated by surface modification of a uniaxially pre-strained PDMS using a hand-held corona discharger followed by strain relaxation. The resulting nanoscale wrinkles overlay on 1) microwrinkled substrate and 2) reflowed microstructures to create anisotropic and hierarchical surface topographies. This electrical discharge assisted wrinkling process for creating multi-scale roughness is accessible in general wet lab environments. Such structures have broad applications in optical gratings, cell mechanics studies, and micro/nanofluidics.