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Asymmetric Complementary Interface for Enhanced Directional Adhesion

  • Author / Creator
    Yang, Zhen
  • Inspired by nature, structured interfaces have been shown to enhance adhesion by trapping crack propagation along the interface. To propagate the trapped crack, more energy input is required externally and therefore the effective fracture toughness is increased. In many applications, directional adhesion is desired where interface separation along different directions requires different fracture energy. One such example is climbing robot: it needs strong adhe- sion to stick their feet on vertical surfaces and weak adhesion to detach the feet while walking. In this work, we investigate a strategy to attain enhanced and directional adhesion using a complementary interface that contains an asymmetric pattern. In particular, the pattern consists of right triangles sep- arated by flat regions. As the crack propagates from left to right, it travels upwards along the vertical side of the triangle, and then downwards along the hypotenuse; as it propagates from right to left, it travels upwards along the hypotenuse, and then downwards along the vertical side. Finite element anal- yses were performed in which the length of the crack tip was extended step by step and the energy release rate G was calculated at each crack length. The G values were compared to that of a flat interface to determine the adhesion enhancement. Our result shows that the fracture toughness of the interface is enhanced by approximately four times, compared with the flat control, for crack propagation from left to right, and the enhancement is larger for crack propagation in the opposite direction. In addition, parametric analyses revealthat the adhesion enhancements in the two opposite directions have differ- iient sensitivities to the changes in the aspect ratio of the triangular pattern. The proposed strategy allows us to achieve enhanced and directional adhesion without modifying the interface chemistry. More importantly, different degree of adhesion asymmetry can be achieved by modulating the aspect ratio of the pattern on the interface, bearing great potential in applications where different levels of adhesion are desired for different purposes.

  • Subjects / Keywords
  • Graduation date
    Spring 2019
  • Type of Item
    Thesis
  • Degree
    Master of Science
  • DOI
    https://doi.org/10.7939/r3-2kjs-tj57
  • License
    Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.