title: Photoswitchable ratchet surface topographies based on self-protonating spiropyran-NIPAAM hydrogels.
abstract: In this work, self-protonating spiropyran-based poly(N-isopropylacrylamide) polymer networks are prepared. These photoresponsive hydrogel coatings can change their surface topography upon exposure with visible light in a neutral environment. Photoresponsive surface-constrained films have been fabricated for which the swelling behavior can be controlled in a reversible manner. In a first step, symmetrical switchable surface topologies with varying cross-link density are obtained by polymerization-induced diffusion. Under light exposure, the areas with low cross-link density swell more than the areas with high cross-link density, thus forming a corrugated surface. Asymmetric ratchet-like photoresponsive surfaces have been prepared on prestructured asymmetric substrates. As a result of thickness variation of the surface-confined hydrogel layer, an asymmetric swelling behavior is obtained. Depending on the cross-link density of the hydrogel, it is possible to switch between a ratchet and flat surface topography or even an inverse ratchet surface by light.
authors.affiliation: Department of Functional Organic Materials and Devices, Chemical Engineering and Chemistry, Eindhoven University of Technology , Den Dolech 2, 5612 AZ Eindhoven, The Netherlands.
authors.forename: Jelle E
authors.initials: JE
authors.lastname: Stumpel
authors.forename: Bartosz
authors.initials: B
authors.lastname: Ziółkowski
authors.forename: Larisa
authors.initials: L
authors.lastname: Florea
authors.forename: Dermot
authors.initials: D
authors.lastname: Diamond
authors.forename: Dirk J
authors.initials: DJ
authors.lastname: Broer
authors.forename: Albertus P H J
authors.initials: AP
authors.lastname: Schenning
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D001578:Benzopyrans / Q000737:chemistry*; D004058:Diffusion; D020100:Hydrogels / Q000737:chemistry*; D007211:Indoles / Q000737:chemistry*; D007536:Isomerism; D008027:Light; D009574:Nitro Compounds / Q000737:chemistry*; D058105:Polymerization; D013499:Surface Properties
chemical_list: D000180:Acrylic Resins; D001578:Benzopyrans; D020100:Hydrogels; D007211:Indoles; D009574:Nitro Compounds; C548873:merocyanine; C088184:spiropyran; C052970:poly-N-isopropylacrylamide