The current research
on gecko-inspired dry adhesives is focused
on micropillar arrays with different terminal shapes, such as flat,
spherical, mushroom, and spatula tips. The corresponding processing
methods are mostly chemical methods, including lithography, etching,
and deposition, which not only are complex, expensive, and environmentally
unfriendly, but also cannot completely ensure microstructural integrity
or performance stability. The present study demonstrates a high-precision,
high-efficiency, and green method for the fabrication of a gecko-inspired
surface, which can promote its application in dexterous robot hands
and mechanical grippers. Based on the bendable lamellar structures
of the gecko, annular wedge adhesive surfaces that stick to the finger
surfaces of dexterous robot hands to improve their load capacity are
proposed and fabricated via a suitable combined processing method
of ultraprecision machining and replica molding. The greater the width,
the higher the replication integrity, and when the minimum width is
20 μm, the replication error is less than 5.5% due to the superior
processing performance of the nickel–phosphorus (Ni–P)
plating of the master mold. The fabricated annular wedge structures
with an optimized width of 20 μm not only exhibit a strong friction
force of up to 35.48 mN under a preload of 20 mN in the GCr15/poly(dimethylsiloxane)
(PDMS) friction pair but also demonstrate an obviously improved anisotropic
friction characteristic of up to λ = 1.36, as the molecular
force exhibits a stronger increase as compared to the decrease of
the mechanical force of the structure with a small width.
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