Interface-engineered carbon nanotube-coated polyurethane for electro- and photo-responsive applications

Shape-memory polyurethane (SMPU) requires integrated multi-stimuli responsiveness and reliable electrical readout to advance beyond reliance on external heaters or slow environmental triggers. Here, we report a polyurethane/carbon nanotube (PU/CNT) system in which interface modification dictates coating quality, electrical continuity, and device performance. Acid oxidation of CNTs generates hydroxyl, epoxide, and carboxyl functionalities, enhancing dispersion stability, while oxygen plasma treatment of PU transiently increases surface energy to enable continuous spin-coating within the activation window. Using ethanol as the medium, serial spin coating forms uniform percolated networks with sheet resistance suitable for Joule heating and electrical readout. Thermal analysis confirms favorable crystallization behavior that supports rapid shape fixation and recovery. The elastomer exhibits excellent shape-memory performance (R_f = 99.5%, R_r = 95.2%), with the conductive layer enabling both electro- and photo-active recovery as well as bending, tensile, and humidity/temperature sensing. Collectively, these results establish a reproducible pathway for manufacturable SMPU devices through the convergence of CNT oxidation, plasma activation, and network morphology control.