title: Phototaxis of Oil Droplets Comprising a Caged Fatty Acid Tightly Linked to Internal Convection.
abstract: We found that novel sub-millimeter-sized photoactive oil droplets of oleic acid bearing a photolabile protecting group, 2-nitrobenzyl oleate (NBO), in basic water exhibited unidirectional motion toward a UV light source. This unidirectional motion can be explained by anisotropic photolysis on a surface of the NBO droplet with low permeability for UV light. Time-dependent changes of the movement under UV irradiation occurred in a cascade manner (still-standing, induction, and active stages). The velocity of the UV-irradiated droplet in the induction stage was small, but it was accelerated sixteen times by the presence of an inner convection structure, which was created by continued photolysis. This characteristic dynamics, which is derived from a supramolecular machinery system towards the external stimulus, may be similar to the phototaxis of a living cell.
authors.affiliation: Department of Chemistry, Faculty of Science, Kanagawa University, 2946 Tsuchiya, Hiratsuka, Kanagawa, 259-1293, Japan. suzuken@kanagawa-u.ac.jp.
authors.forename: Kentaro
authors.identifier: http://orcid.org/0000-0003-0966-3532
authors.initials: K
authors.lastname: Suzuki
authors.affiliation: Department of Chemistry, Faculty of Science, Kanagawa University, 2946 Tsuchiya, Hiratsuka, Kanagawa, 259-1293, Japan.|Toyota Physical and Chemical Research Institute, 41-1, Yokomichi, Nagakute, Aichi, 480-1192, Japan.
authors.forename: Tadashi
authors.initials: T
authors.lastname: Sugawara
mesh_terms: D018481:Convection; D007700:Kinetics; D009038:Motion; D009578:Nitrobenzenes / Q000737:chemistry*; D019301:Oleic Acid / Q000737:chemistry*; D009829:Oleic Acids / Q000737:chemistry*; D010316:Particle Size; D010782:Photolysis; D000071444:Phototaxis; D014466:Ultraviolet Rays; D014867:Water / Q000737:chemistry*
chemical_list: C000625980:2-nitrobenzyl oleate; D009578:Nitrobenzenes; D009829:Oleic Acids; D014867:Water; D019301:Oleic Acid
keywords: active matter; droplets; photolysis; phototaxis; self-assembly