ABSTRACT
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.
ABSTRACT
Recent advances achieved in triboelectric nanogenerators (TENG) focus on boosting power generation and conversion efficiency. Nevertheless, obstacles concerning economical and biocompatible utilization of TENGs continue to prevail. Being an abundant natural biopolymer from marine crustacean shells, chitosan enables exciting opportunities for low-cost, biodegradable TENG applications in related fields. Here, the development of biodegradable and flexible TENGs based on chitosan is presented for the first time. The physical and chemical properties of the chitosan nanocomposites are systematically studied and engineered for optimized triboelectric power generation, transforming the otherwise wasted natural materials into functional energy devices. The feasibility of laser processing of constituent materials is further explored for the first time for engineering the TENG performance. The laser treatment of biopolymer films offers a potentially promising scheme for surface engineering in polymer-based TENGs. The chitosan-based TENGs present efficient energy conversion performance and tunable biodegradation rate. Such a new class of TENGs derived from natural biomaterials may pave the way toward the economically viable and ecologically friendly production of flexible TENGs for self-powered nanosystems in biomedical and environmental applications.
