Writing Wrinkles on Poly(dimethylsiloxane) (PDMS) by Surface Oxidation with a CO₂ Laser Engraver

Surface wrinkles formed by the buckling of a strained stiff layer attached to a soft elastomer foundation have been widely used in a variety of applications. Micropatterning of wrinkled topographies is, however, limited by process/system complexities. In this article, we report an approach to write surface wrinkles with desired pattern geometries on poly(dimethylsiloxane) (PDMS) elastomers using a commercial infrared laser engraver with a spot size of 127 μm. Wrinkled micropatterns with wavelength from <50 to >300 μm were obtained in minutes without using special facilities or atmospheres. The minimal achievable pattern sizes of one-dimensional and two-dimensional patterns and the change of the minimal achievable pattern size with wrinkle orientation were investigated under a given set of operating parameters. Sub-spot size patterning was also demonstrated. To reduce surface cracking, a typical problem in large-area wrinkle patterning, a patterning scheme that separates neighboring laser exposure areas by nonexposure gaps was developed. In addition, micropatterns with gradient wrinkles were created on the surface. This is the first report that patterns microscale surface wrinkles on elastomer surfaces using infrared laser irradiation. The simple and versatile approach is expected to provide a fast yet controllable way to create wrinkled micropatterns at low cost to facilitate a broad array of studies in surface engineering, cellular biomechanics, and optics.