TY  - JOUR
A1  - Karageorgiev, Peter
A1  - Neher, Dieter
A1  - Schulz, Burkhard
A1  - Stiller, Burkhard
A1  - Pietsch, Ullrich
A1  - Giersig, Michael
A1  - Brehmer, Ludwig
T1  - From anisotropic photo-fluidity towards nanomanipulation in the optical near-field
N2  - 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
Y1  - 2005
SN  - 1476-1122
ER  - 
TY  - JOUR
A1  - Stiller, Burkhard
A1  - Karageorgiev, Peter
A1  - Geue, Thomas
A1  - Morawetz, Knut
A1  - Saphiannikova, Marina
A1  - Mechau, Norman
A1  - Neher, Dieter
T1  - Optically induced mass transport studied by scanning near-field optical- and atomic force microscopy
N2  - Some functionalised thin organic films show a very unusual property, namely the light induced material transport. This effect enables to generate three-dimensional structures on surfaces of azobenzene containing films only caused by special optical excitation. The physical mechanisms underlying this phenomenon have not yet been fully understood, and in addition, the dimensions of structures created in that way are macroscopic because of the optical techniques and the wavelength of the used light. In order to gain deeper insight into the physical fundamentals of this phenomenon and to open possibilities for applications it is necessary to create and study structures not only in a macroscopic but also in nanometer range. We first report about experiments to generate optically induced nano structures even down to 100 nm size. The optical stimulation was therefore made by a Scanning Near-field Optical Microscope (SNOM). Secondly, physical conditions inside optically generated surface relief gratings were studied by measuring mechanical properties with high lateral resolution via pulse force mode and force distance curves of an AFM
Y1  - 2004
SN  - 0204-3467
ER  -