Investigating the normal and tangential peeling behaviour of gecko spatulae using a coupled adhesion-friction model
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The present work investigates the normal and tangential peeling behaviour of a gecko spatula computationally using a coupled adhesion-friction model. The objective is to explain the strong attachment and easy detachment behaviour of the spatulae as well as to understand the principles behind their optimum design. Using a computational model, it is shown that the "frictional adhesion" behaviour, until now only observed from seta to toe levels, is also present at the spatula level. The model also shows that there is an optimum range of spatula pad thickness for which, irrespective of the peeling angle, the spatula detaches at a constant angle known as critical detachment angle. It is shown that the spatula readily detaches from the substrate by changing its shaft angle and then peeling vertically like a tape. Additionally, it is found that friction increases the attachment forces, while the detachment forces are fairly unaffected. Since the present computational model is not limited by the geometrical, kinematical, and material restrictions of theoretical models, it can be employed to study and analyse the adhesion behaviour of many similar biological adhesive systems.
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