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Shear Adhesion of Tapered Nanopillar Arrays
journal contribution
posted on 2018-03-23, 20:06 authored by Younghyun Cho, Helen K. Minsky, Yijie Jiang, Kaiyang Yin, Kevin T. Turner, Shu YangTapered nanopillars with various
cross sections, including cone-shaped, stepwise, and pencil-like structures
(300 nm in diameter at the base of the pillars and 1.1 μm in
height), are prepared from epoxy resin templated by nanoporous anodic
aluminum oxide (AAO) membranes. The effect of pillar geometry on the
shear adhesion behavior of these nanopillar arrays is investigated
via sliding experiments in a nanoindentation system. In a previous
study of arrays with the same geometry, it was shown that cone-shaped
nanopillars exhibit the highest adhesion under normal loading while
stepwise and pencil-like nanopillars exhibit lower normal adhesion
strength due to significant deformation of the pillars that occurs
with increasing indentation depth. Contrary to the previous studies,
here, we show that pencil-like nanopillars exhibit the highest shear
adhesion strength at all indentation depths among three types of nanopillar
arrays and that the shear adhesion increases with greater indentation
depth due to the higher bending stiffness and closer packing of the
pencil-like nanopillar array. Finite element simulations are used
to elucidate the deformation of the pillars during the sliding experiments
and agree with the nanoindentation-based sliding measurements. The
experiments and finite element simulations together demonstrate that
the shape of the nanopillars plays a key role in shear adhesion and
that the mechanism is quite different from that of adhesion under
normal loading.
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Tapered Nanopillar Arrays Tapered nanopillarsnanopillar arraysAAOFinite element simulationsshear adhesion increasespencil-like nanopillar arraypencil-like nanopillars exhibitexperimentnanoporous anodic aluminum oxideindentation depthshear adhesion strength1.1 μ mshear adhesion behaviorcone-shaped nanopillars exhibit
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