Precise Controlling of Friction and Adhesion on Reprogrammable Shape Memory Micropillars.

Microstructured surfaces with stimuli-responsive performances have aroused great attention in recent years, but it still remains a significant challenge to endow surfaces with precisely controlled morphological changes in microstructures, so as to get the precise control of regional properties (e.g., friction, adhesion). Herein, a kind of carbonyl iron particle-doped shape memory polyurethane micropillar with precisely controllable morphological changes is realized, upon remote near-infrared light (NIR) irradiation. Owing to the reversible transition of micropillars between bent and upright states, the micro-structured surface exhibits precisely controllable low-to-high friction transitions, together with the changes of friction coefficient ranging from ∼0.8 to ∼1.2. Hence, the changes of the surface friction even within an extremely small area can be precisely targeted, under local NIR laser irradiation. Moreover, the water droplet adhesion force of the surface can be reversibly switched between ∼160 and ∼760 μN, demonstrating the application potential in precisely controllable wettability. These features indicate that the smart stimuli-responsive micropillar arrays would be amenable to a variety of applications that require remote, selective, and on-demand responses, such as a refreshable Braille display system, micro-particle motion control, lab-on-a-chip, and microfluidics.