Self-assembled Dynamic 3D Fingerprints in Liquid-Crystal Coatings Towards Controllable Friction and Adhesion

Authors

  • Dr. Danqing Liu,

    1. Laboratory of Functional Organic Materials & Devices (SFD), Department of Chemical Engineering & Chemistry, Eindhoven University of Technology, Den Dolech 2, 5612 AZ Eindhoven (The Netherlands)
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  • Dr. Dirk J. Broer

    Corresponding author
    1. Laboratory of Functional Organic Materials & Devices (SFD), Department of Chemical Engineering & Chemistry, Eindhoven University of Technology, Den Dolech 2, 5612 AZ Eindhoven (The Netherlands)
    2. Institute for Complex Molecular Systems (ICMS), P.O. Box 513, 5600 MB Eindhoven (The Netherlands)
    • Laboratory of Functional Organic Materials & Devices (SFD), Department of Chemical Engineering & Chemistry, Eindhoven University of Technology, Den Dolech 2, 5612 AZ Eindhoven (The Netherlands)===

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  • The results presented are part a research program financed by the Dutch Polymer Institute (DPI), project no 775.

Abstract

Chiral-nematic polymer network coatings form a “fingerprint” texture through self-assembly. For this purpose the molecular helix of the coating is oriented parallel to the substrate. The coating has a flat surface but when actuated by light in the presence of a copolymerized azobenzene compound, 3D fingerprint structures appear in the coating. The helix forms protrusions at the positions where the molecules are aligned parallel to the surface and withdraws at the positions where the orientation is perpendicular. This process proceeds rapidly and is reversible, that is, the fingerprint-shaped protrusions disappear when the light is switched off. The texture in the on-state resembles that of a human fingerprint and is used to manipulate the gripping friction of a robotic finger. The friction coefficient drops by a factor of four to five when the fingerprint switched on because of reduced surface contacts.

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