Mechanics of bio-inspired attachment systems contacting with rough surface: effect of spring orientation angle on hierarchical spring model

It is known that due to the asymmetrically designed structure of seta, gecko makes an attachment at 30° and detachment at 90° and achieves its detachment by changing orientation angle of seta from 30° to 90°. In this study, it is shown how pulling orientation affects pull-off force for gecko hierarchy using spring model during detachment from rough surface and then how to achieve easy and quick switch between attachment and detachment. This study adds the change of spring orientation angle to hierarchical spring model and extends it for determining the effect of orientation angle on the pull-off force. One-, two-, and three-level hierarchical models for gecko lamella consisting of seta, branches, and spatula contacting with the rough surface have been used. This study will provide us information about pull-off forces from rough surfaces and help to imitate and produce in particular gecko-like devices, reusable products and in general nanomaterials and nanodevices.