Fabrication and Adhesion Test of the Secondary Structure with Large End

Firstly, micrometer-sized silicone- and polyurethane- based primary structures of adhesive arrays are prepared
by injection molding in vacuum, then silicone-based viscous membrane is coated onto the end of the primary array, and thus
an adhesive array of secondary structure is formed. The tangent adhesion performance of those arrays is tested by microfriction
testing machine (UMT), and the results show that, the large end structure increases the effective contact area and
also improves the tangential adhesion properties; the tangent force firstly increases in a short sliding distance, then decreases,
finally keeps stable in the following slide; the maximum tangential adhesion force is generated in the sliding distance of 1 mm;
as the normal load increases, the adhesion force produced by the adhesive array increases, and decreases after the normal load
exceeds a certain range; under the preload of 15 mN, the generated maximum tangential adhesion force is 84.668 mN; the
maximum tangent adhesion strength of sliding along the seta is around 1.140 N/cm², which is significantly higher than that
of sliding against the seta, and in that direction, the maximum tangent adhesion strength is around 0.223 N/cm².