Smart UV/Visible light responsive polymer surface switching reversibly between superhydrophobic and superhydrophilic

Smart surface which can reversibly switch between hydrophobic and hydrophilic state has great potential application in areas such as microfluidic, sensor, medical devices, etc. In this study, one approach for chemically grafting nanoporous layer of azobenzene based polymer nanoparticles on cyclic olefin co-polymer (COC) substrates has been realized via plasma and UV induced surface grafting polymerization of inverse microemulsion containing 7-[(trifluoromethoxyphenylazo)phenoxy] acrylic acid (TFMPAA), 1-vinyl-2-pyrrolidinone (NVP), and cross-linker N,N′-methylenebis (acrylamide) (MBA). During the surface initiated grafting polymerization of the inverse microemulsion, polymer nanoparticles is generated and accumulated on surface, forming a porous photosensitive layer which enhances the surface roughness at the same time. In our study, maximum static water contact angle (WCA) of 150° was observed at trans state of grafted TFMPAA, which transformed to cis state under 365nm UV illumination. At cis state, due to the higher free energy of TFMPAA, superhydrophilic surface (WCA less than 5°) was achieved and can switch back to superhydrophobic state by 440nm light illumination. Also, the grafted layer showed good adhesive strength and durability in our air and water exposure tests. The positive results suggest that porous TFMPAA grafted plastic substrates is a promising new material for microfluidic, cell culture, intelligent membranes and biosensor devices. A photo responsive polymer surface was fabricated via plasma and UV induced surface grafting polymerization of a new azobenzene based monomer (TFMPAA) in microemulsion form. The grafted layer can endows the polymer surface with photo responsive property which can reversibly switch between superhydrophobic and superhydrophilic upon UV and visible light irradiation. The positive results suggest that porous TFMPAA grafted plastic substrates is a promising new material for microfluidic, cell culture, intelligent membranes and biosensor devices. [Display omitted] •A new method was proposed for fabrication of polymer surface with light-triggered reversibly switchable wettability.•The modified surface showed stable and robust photo-responsive property in more than 30days.•Applications in microfluidic devices was demonstrated in this research