Repeated shape recovery of clustered nanopillars by mechanical pulling

High-aspect-ratio (HAR) nanopillars are of interest for wetting, adhesion, and energy harvesting due to their superior surface properties, including large surface area and high compliance. However, their intrinsically low mechanical stability has been a major obstacle for practical applications that require repeated use and in wet and humid environments. Herein, we show a method that can recover the clustered or deformed HAR nanopillars to their original shapes by taking advantage of the mechanical compliance of the nanopillars toward pulling during a demolding process. The pillars can be repeatedly clustered and recovered many times. Our method is simple yet powerful to recover the clustered nanopillars over a large area (7 × 10 cm²). By taking advantage of the different optical properties of the clustered pillars vs. the straight ones, we demonstrate display and erasing of patterns and tunable wettability by stamping the nanopillars to induce clustering, followed by shape recovery via demolding of the pillars.