Here we reported temperature-controlled moisture responsive wrinkled patterns based on bilayer system, and explore its regulation mechanism and applications. The bilayer wrinkling system is comprising a copolymer P(IMAN-co-NIPAM-co-OEGMA) containing 1-vinyl-3-anthracenemethyl imidazolium chloride (IMAN), N-isopropylacrylamide (NIPAM) and poly(ethylene glycol) methyl ether methacrylate (OEGMA) as the skin layer and poly(dimethylsiloxane) (PDMS) as the substrate. After photodimerization of the AN group, the polymer network is crosslinked, and the modulus of the top film increases. According to the linear buckling theory, random wrinkles are formed under thermal treatment and subsequent cooling to room temperature owing to the mismatch in the moduli and thermal expansion coefficients between the stiff skin layer and the soft substrate. First, the photodimerization of AN group endows the system with the ability of region selective wrinkling. If the irradiation process is performed with a photomask, the exposed regions are rigid enough for wrinkles forming, while the unexposed areas are not. Furthermore, surface wrinkles caused strong light scattering while the flat surface limit it, which affects the visibility of an object. Thus, we could fabricate various images utilizing the selective wrinkled patterns. Second, the NIPAM-containing polymer chain endows the wrinkles with temperature-controlled moisture response. Under room temperature, the wrinkles can be eliminated by moisture, which is caused by the decreasing modulus and stress relaxation during absorbing moisture; while under a higher temperature, the wrinkles cannot be driven by moisture because the copolymer of top layer becomes hydrophobic, which is demonstrated by experimental results such as the laser scanning confocal microscope images. Furthermore, the wrinkled images and the transparence can be controlled by moisture and temperature during the switch between wrinkled and flat states. Besides, the poly(ethylene glycol) methyl ether methacrylate (OEGMA) is involved to tune the mechanical properties. The photosensitive and temperature- controlled moisture responsive wrinkled patterns may find potential applications in moisture sensing, smart display or smart windows.

Key words: dynamic wrinkle pattern, moisture response, temperature-regulation, regulation mechanism, moisture sensing