alexa Why are so many adhesive pads hairy?


Journal of Physical Chemistry & Biophysics

Author(s): Federle W, Federle W, Federle W, Federle W

Abstract Share this page

Abstract Many arthropods and vertebrates possess tarsal adhesive pads densely covered with setae. The striking morphological convergence of ;hairy' pads in lizards, spiders and several insect orders demonstrates the advantage of this design for substrate adhesion. Early functional explanations of hairy adhesive organs focused on the performance on rough substrates, where flexible setae can make more intimate contact. Recent theoretical and experimental work shows that the hairy design can also help to achieve self-cleaning properties, controllable detachment and increased adhesion. Several arguments have been proposed to explain why adhesive forces are maximised. First, the ;Force scaling' hypothesis states that when adhesive forces scale linearly with the dimensions of the contact, adhesion is increased by dividing the contact zone into many microscopic subunits. Second, the ;Fracture mechanics' argument implies that adhesion is maximised when the size of adhesive contacts is smaller than the critical crack length. Third, the ;Work of adhesion' model suggests that adhesion increases due to the bending and stretching of setae and associated energy losses during detachment. Several morphological traits of hairy adhesive pads can be explained by the need to maximise the work of adhesion, while avoiding the sticking of setae to each other (self-matting). Firstly, if setae are oblique and convex toward the foot tip as typical of most hairy pads, arrays should achieve greater adhesion. Secondly, a branched seta morphology not only confers the advantage that setae can adapt to roughness at different length scales but also prevents self-matting and increases the work of adhesion. It is predicted from the ;Work of adhesion' model that adhesion of pads with unbranched setae cannot be increased by subdividing the contact zone into ever finer subcontacts, because this would increasingly cause self-matting. However, contact splitting can increase adhesion if setae are branched. The greater density of setae in large animals has been interpreted by ;Force scaling'. However, the existing data can be explained by the effect of seta branching and by a fundamental difference between ;wet' and ;dry' adhesive systems. As insects employ adhesive fluids, they can cope with small-scale surface roughness even with relatively blunt seta tips, whereas the dry systems of lizards and spiders require extremely fine endings. This article was published in J Exp Biol and referenced in Journal of Physical Chemistry & Biophysics

Relevant Expert PPTs

Relevant Speaker PPTs

Recommended Conferences

  • 5th International Conference and Exhibition on Physical Medicine & Rehabilitation
    Aug 14-16, 2017 Los Angeles, USA
  • 2nd International Conference on Physics
    Aug 28-30, 2017 Brussels, Belgium
  • 5th Global Chemistry Congress
    September 04-06, 2017 London, UK
  • 3rd World Chemistry Conference
    September 11-12, 2017 Dallas, USA
  • Global Conference on Physical Chemistry
    September 18-19, 2017 Dublin, Ireland
  • 2nd International Conference on Applied Chemistry  
    October 16-17, 2017 Toronto, Canada
Peer Reviewed Journals
Make the best use of Scientific Research and information from our 700 + peer reviewed, Open Access Journals
International Conferences 2017-18
Meet Inspiring Speakers and Experts at our 3000+ Global Annual Meetings

Contact Us

© 2008-2017 OMICS International - Open Access Publisher. Best viewed in Mozilla Firefox | Google Chrome | Above IE 7.0 version