Evidence for capillarity contributions to gecko adhesion from single spatula nanomechanical measurements

We report only pull-off forces of single spatulae; in cases where two spatulae detached simultaneously, the force value was halved

G. Huber

2005

Scholarcy highlights

  • The hairy attachment system on a gecko‚Äôs toes, consisting of one billion spatulae in the case of Gekko gecko [Ruibal, R. & Ernst, V. J
  • This report details measurements of the adhesion force exerted by a single gecko spatula for various atmospheric conditions and surface chemistries
  • The method is the same as described in our previous paper. It is based on detachment experiments with an atomic force microscopy of spatulae isolated by micromachining with a focused ion beam
  • Our study demonstrates that humidity influences gecko adhesion on the spatular level
  • Its relative contribution depends on air humidity and substrate hydrophilicity
  • Such an effect can be explained, at least semiquantitatively, by considering water monolayers adsorbed between spatula and substrate. The implications of these findings have potentially high relevance in biology and engineering: studies of bioadhesive mechanisms must account for the possible influence of humidity, and capillary effects should be optimized in the biomimetic design of artificial attachment systems
  • The detachment force in the presence of water is almost six times smaller than for the same experiment at ambient humidity and is independent of contact angle of the substrate

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