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From anisotropic photo-fluidity towards nanomanipulation in the optical near-field

Nature Materials volume 4, pages 699–703 (2005)Cite this article

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.

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Figure 1: Penetration curves of a silicon nitride tip in a spin-coated film of pDR1M under continuously increasing/decreasing load (|dF/dt|=1,200 nN s−1).
Figure 2: Response of the surface of a pDR1M film to a constant load for several minutes.
Figure 3: One-direction fluidity of a pDR1M film.
Figure 4: Photofluidization with a resolution of about 20 nm.
Figure 5: Trapping and transfer.

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Acknowledgements

We thank J. Stumpe for discussions, K. Morawetz and O. Henneberg for the preparation of samples, A. Kosiorek and W. Kandulski for the SEM images of the probe tips. P.K. thanks V. Karageorgieva for encouragement during the experimental work and assistance with preparing the manuscript, and S. Schrader for support. The Ministerium für Wissenschaft, Forschung und Kultur of Brandenburg funded this work.

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  1. Institute of Physics, University of Potsdam, Am Neuen Palais 10, 14469, Potsdam, Germany

    Peter Karageorgiev, Dieter Neher, Burkhard Schulz, Burkhard Stiller, Ullrich Pietsch & Ludwig Brehmer

  2. Center of Advanced European Studies and Research (CAESAR), Ludwig-Erhard-Allee 2, 53175, Bonn, Germany

    Peter Karageorgiev & Michael Giersig

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Karageorgiev, P., Neher, D., Schulz, B. et al. From anisotropic photo-fluidity towards nanomanipulation in the optical near-field. Nature Mater 4, 699–703 (2005). https://doi.org/10.1038/nmat1459

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