title: From anisotropic photo-fluidity towards nanomanipulation in the optical near-field.
abstract: An increase in random molecular vibrations of a solid owing to heating above the melting point leads to a decrease in its long-range order and a loss of structural symmetry. Therefore conventional liquids are isotropic media. Here we report on a light-induced isothermal transition of a polymer film from an isotropic solid to an anisotropic liquid state in which the degree of mechanical anisotropy can be controlled by light. Whereas during irradiation by circular polarized light the film behaves as an isotropic viscoelastic fluid, it shows considerable fluidity only in the direction parallel to the light field vector under linear polarized light. The fluidization phenomenon is related to photoinduced motion of azobenzene-functionalized molecular units, which can be effectively activated only when their transition dipole moments are oriented close to the direction of the light polarization. We also describe here how the photofluidization allows nanoscopic elements of matter to be precisely manipulated.
authors.affiliation: Institute of Physics, University of Potsdam, Am Neuen Palais 10, 14469 Potsdam, Germany. karageorgiev@caesar.de
authors.forename: Peter
authors.initials: P
authors.lastname: Karageorgiev
authors.forename: Dieter
authors.initials: D
authors.lastname: Neher
authors.forename: Burkhard
authors.initials: B
authors.lastname: Schulz
authors.forename: Burkhard
authors.initials: B
authors.lastname: Stiller
authors.forename: Ullrich
authors.initials: U
authors.lastname: Pietsch
authors.forename: Michael
authors.initials: M
authors.lastname: Giersig
authors.forename: Ludwig
authors.initials: L
authors.lastname: Brehmer
mesh_terms: D016880:Anisotropy; D003460:Crystallization / Q000379:methods*; D008027:Light; D008422:Materials Testing; D044085:Microfluidics / Q000379:methods*; D008846:Micromanipulation / Q000379:methods*; D036103:Nanotechnology / Q000379:methods*; D010777:Photochemistry / Q000379:methods*; D011108:Polymers / Q000032:analysis / Q000737:chemistry* / Q000528:radiation effects*; D012996:Solutions
chemical_list: D011108:Polymers; D012996:Solutions