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Fast liquid-crystal elastomer swims into the dark

Nature Materials volume 3, pages 307–310 (2004)Cite this article

Abstract

Liquid-crystal elastomers (LCEs) are rubbers whose constituent molecules are orientationally ordered. Their salient feature is strong coupling between the orientational order and mechanical strain1. For example, changing the orientational order gives rise to internal stresses, which lead to strains and change the shape of a sample. Orientational order can be affected by changes in externally applied stimuli such as light. We demonstrate here that by dissolving—rather than covalently bonding—azo dyes into an LCE sample, its mechanical deformation in response to non-uniform illumination by visible light becomes very large (more than 60° bending) and is more than two orders of magnitude faster than previously reported2,3,4. Rapid light-induced deformations allow LCEs to interact with their environment in new and unexpected ways. When light from above is shone on a dye-doped LCE sample floating on water, the LCE 'swims' away from the light, with an action resembling that of flatfish such as skates or rays. We analyse the propulsion mechanism in terms of momentum transfer.

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Figure 1: The chemical structures of the nematic LCE and dye.
Figure 2: The optomechanical response of an LCE sample.
Figure 3: The interaction of a dye-doped LCE sample with a liquid.
Figure 4: Illustration of the mechanism underlying the locomotion of the dye-doped LCE sample.

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Acknowledgements

This work was supported by the US National Science Foundation and the Department of Energy. We thank T. Toth-Katona for his help with Fig. 4a.

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Authors and Affiliations

  1. Liquid Crystal Institute, Kent State University, Kent, 44242, Ohio, USA

    Miguel Camacho-Lopez & Peter Palffy-Muhoray

  2. School of Physics and Astronomy, University of St Andrews, St Andrews, KY16 9SS, UK

    Miguel Camacho-Lopez

  3. Institute für Macromoleculare Chemie, Albert-Ludwigs Universität, Freiburg, D-79104, Germany

    Heino Finkelmann

  4. Courant Institute of Mathematical Sciences, New York University, New York, 10012, New York, USA

    Michael Shelley

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  1. Miguel Camacho-Lopez
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Correspondence to Peter Palffy-Muhoray.

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Camacho-Lopez, M., Finkelmann, H., Palffy-Muhoray, P. et al. Fast liquid-crystal elastomer swims into the dark. Nature Mater 3, 307–310 (2004). https://doi.org/10.1038/nmat1118

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