Water-Repellent, Surface-Adaptive, and Switchable Adhesive Patch Using Microstructured Shape Memory Polymers

Underwater pull-off adhesion and adhesion-switching performance were quantified using a CellScale UniVert with a custom fixture (substrate holder, sample holder, vertically movable jig). Substrates were mounted to the lower holder with double-sided tape and 1×1 cm^2 MSMP adhesive samples were mounted to the upper holder (adhesive facing down). For wet adhesion tests, the substrate was immersed in a small water bath placed on the sample holder. Contact was initiated by applying a 50 kPa preload using calibrated weights (preload chosen because pull-off force saturated at this level), after which the holder was connected to the UniVert jig via a fishing line and retracted upward at a constant speed of 2 mm/s until detachment while recording pull-off force. For the adhesion “ON” state, samples were pressed under 50 kPa while heated above Tm (≈65°C, monitored by type-K thermocouple; maintained in ~60–70°C rubbery regime) using a heat gun, then cooled to 30°C under preload to fix the adapted geometry before pull-off. For the adhesion “OFF” state, samples were reheated to 65°C without additional preload prior to detachment so that the glassy/rubbery transition governed switching rather than reloading conditions.