Navigation Links
Humidity makes gecko feet stickier
Date:10/14/2010

Human adhesives are famed for their fallibility. Gooey glues soon lose their grip, are easily contaminated and leave residues behind. But not gecko feet. Geckos can cling on repeatedly to the smoothest surfaces thanks to the self-cleaning microscopic spatula-shaped hairs (setae) that coat the soles of their feet. Back in 2002, Kellar Autumn found that these dry hairs are in such intimate contact with surfaces that the reptiles 'glue' themselves on by van der Waals forces with no need for fluid adhesives. More recent studies had suggested that geckos might benefit from additional adhesion in humid environments through capillary action provided by microscopic droplets of water sandwiched between setae and the surface. But Autumn wasn't so sure, so he and his lab at Lewis and Clark College and the University of Washington, USA, began testing gecko grip to find out how increasing humidity helps them hold tight Autumn publishes his team's discovery that humidity helps geckos grip tighter by softening the surface of their feet on 15 October 2010 in The Journal of Experimental Biology at http://jeb.biologists.org.

Knowing that geckos replace lost setae when they moult, Autumn, his postdoc Jonathan Puthoff, and Matt Wilkinson collected patches of the 'sticky' hairs from gecko feet and attached them to a mechanical testing device, known as 'Robotoe', that reproduces the way the reptile drags its foot as it contacts a surface. Dragging the setae across two surfaces (one that repelled water and another that attracted water) at different velocities and in environments ranging from 10% to 80% humidity, the team tested whether microscopic water bridges formed in high humidity were helping the geckos hang on. They reasoned that if the reptiles were using microscopic water bridges then the setae would bond more tightly to the surface that attracted water than the surface that repelled water. But when they measured the setae's adhesion and friction it was essentially the same on the two surfaces. And when the team compared the adhesion of setae that were moving too fast to form water bridges with that of slowly moving feet that could possibly form water bridges, there was no difference. The geckos were not supplementing their van der Waals attachment forces with capillary forces from water bridges. So how were they holding on tighter?

Graduate student Michael Prowse decided to take a closer look at the material properties of the reptile's feet. Knowing that setae are composed of keratin and keratin is softened by high humidity, Autumn wondered whether having softer setae could improve the reptiles' contact with surfaces and increase their van der Waals adhesion. The team decided to measure the setae's softness and how it changed as the humidity rose.

Repeatedly stretching and releasing a strip of setae at three different rates (0.5, 5 and 10 Hz) in environments ranging from 10% to 80% humidity, Autumn's team measured the force transmitted through the strip to calculate the strip's elastic modulus how much elastic energy is stored to see how it changed. As the humidity rose, the elastic modulus decreased by 75% and the strip of setae became softer. So the strip of setae became more deformable as the humidity rose, but could the increased softness explain the gecko's improved attachment under damp conditions?

Puthoff built a mathematical model to see if softer, more deformable, setae could explain the gecko's improved attachment at high humidity and found that it did. Not only did increased softness strengthen the contact between the setae and the surface but also it made it easier for the reptile to peel its foot off. So instead of improving gecko's attachment through microscopic bridges, higher humidity softens the setae that coat the reptile's feet to help them hold fast and peel free with ease.


'/>"/>

Contact: Kathryn Knight
kathryn@biologists.com
44-787-634-4333
The Company of Biologists
Source:Eurekalert

Related biology news :

1. Genomic haircut makes worlds tiniest genome even smaller: UBC research
2. Pitt/Iowa team finds cellular structural molecule can be toxic: Makes pneumonia worse
3. Neuronal diversity makes a difference, says Carnegie Mellon study
4. What makes a good egg and healthy embryo?
5. Selenium makes more efficient solar cells
6. Why (smart) practice makes perfect
7. New retrieval method makes studying cancer proteins easier
8. Wellcome-Wolfson partnership makes £30 million investment in UK scientific infrastructure
9. Flower power makes tropics cooler, wetter
10. ESA makes first GOCE dataset available
11. Innovative MSU research makes lake and stream conservation more effective
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:3/30/2017)... -- Trends, opportunities and forecast in this market to ... AFIS, iris recognition, facial recognition, hand geometry, vein recognition, ... industry (government and law enforcement, commercial and retail, health ... and by region ( North America , ... , and the Rest of the World) ...
(Date:3/28/2017)... 2017 The report "Video Surveillance ... Servers, Storage Devices), Software (Video Analytics, VMS), and Service ... Forecast to 2022", published by MarketsandMarkets, the market was ... projected to reach USD 75.64 Billion by 2022, at ... base year considered for the study is 2016 and ...
(Date:3/24/2017)... The Controller General of Immigration from Maldives Mr. Mohamed Anwar ... the prestigious international IAIR Award for the most innovative high security ePassport ... ... Maldives Immigration Controller General, Mr. ... on the right) have received the IAIR award for the "Most innovative ...
Breaking Biology News(10 mins):
(Date:6/23/2017)... ... June 23, 2017 , ... Ken Hanson, a medical imaging ... Instrumente USA, have been selected as this year’s recipients of two top awards from ... been invited along with other honorees to accept their awards at a banquet in ...
(Date:6/22/2017)... ... 21, 2017 , ... Beaker, the industry’s pioneer in developing ... sciences industry, today announces a strategic partnership with Alcami Corporation, a leading global ... Beaker’s expertise in executive recruitment solutions, providing Alcami with access to the best ...
(Date:6/22/2017)... ... June 22, 2017 , ... AESKU.GROUP, ... DST Diagnostische Systeme & Technologien GmbH, thereby expanding its product portfolio to include ... hay fever, urticaria, asthma, atopic eczema or a food allergy. Allergies are escalating ...
(Date:6/22/2017)... King of Prussia, PA (PRWEB) , ... June ... ... bringing industry knowledge and superior results to clients throughout the biopharma and life ... the rapid changes the industry is seeing. Tunnell’s Kip Wolf will be speaking ...
Breaking Biology Technology: