BULLETIN of the

POLISH ACADEMY of SCIENCES

TECHNICAL SCIENCES

 BULLETIN of the POLISH ACADEMY of SCIENCES: TECHNICAL SCIENCES
Volume 55, Issue 2, June 2007

Micro and Nano-scale mechanics
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pp 141 - 150

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Bio-inspired mechanics of bottom-up designed hierarchical materials: robust and releasable adhesion systems of gecko

H. YAO and H. GAO
To explore the basic principles of hierarchical materials designed from nanoscale and up, we have been studying the mechanics of robust and releasable adhesion nanostructures of gecko [1]. On the question of robust adhesion, we have introduced a fractal-like hierarchical hair model to show that structural hierarchy allows the work of adhesion to be exponentially enhanced as the level of structural hierarchy is increased. We show that the nanometer length scale plays an essential role in the bottom-up design and, baring fracture of hairs themselves, a hierarchical hair system can be designed from nanoscale and up to achieve flaw tolerant adhesion at any length scales. For releasable adhesion, we show that elastic anisotropy leads to orientation-dependent adhesion strength. Finite element calculations revealed that a strongly anisotropic attachment pad in contact with a rigid substrate exhibits essentially two levels of adhesion strength depending on the direction of pulling.
  
Key words: 

nanotechnology, nanoengineering, bio-inspired mechanics, bottom-up design, hierarchical materials, adhesion,
biological material, contact mechanics, anisotropic materials
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