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Physics of suction cups

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We have developed a theory of air leakage at interfaces between two elastic solids with application to suction cups in contact with randomly rough surfaces. We present an equation for the airflow in narrow constrictions which interpolates between the diffusive and ballistic (Knudsen) air-flow limits. To test the theory, we performed experiments using two different suction cups, made from soft polyvinylchloride (PVC), in contact with sandblasted polymethylmethacrylate (PMMA) plates. We found that the measured time to detach (lifetime) of the suction cups was in good agreement with theory, except for surfaces with a root-mean-square (rms) roughness below ≈1 μm, where diffusion of plasticizer from the PVC to the PMMA surface caused blockage of critical constrictions. The suction cup volume, stiffness, and elastic modulus have a huge influence on the air leakage and hence the failure time of the cups. Based on our research we propose an improved biomimetic design of suction cups that could show improved failure times with varying degrees of roughness under dry and wet environments.

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The article was received on 19 Aug 2019, accepted on 16 Oct 2019 and first published on 17 Oct 2019

Article type: Paper
DOI: 10.1039/C9SM01679A
Soft Matter, 2019, Advance Article

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    Physics of suction cups

    A. Tiwari and B. N. J. Persson, Soft Matter, 2019, Advance Article , DOI: 10.1039/C9SM01679A

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