Navigation Links
Urban myth disproved: Fingerprints do not improve grip friction
Date:6/11/2009

Fingerprints mark us out as individuals and leave telltale signs of our presence on every object that we touch, but what are fingerprints really for? According to Roland Ennos, from the University of Manchester, other primates and tree-climbing koalas have fingerprints and some South American monkeys have ridged pads on their tree-gripping tails, so everyone presumed that fingerprints are there to help us hang onto objects that we grasp. This theory that fingerprints increase friction between the skin and whatever we grab onto has been around for over 100 years, but no one had directly tested the idea. Having already figured out why we have fingernails, Ennos was keen to find out whether fingerprints improve our grip, so he recruited Manchester undergraduate Peter Warman to test out fingerprint friction and publishes his results on June 12 2009 in the Journal of Experimental Biology at http://jeb.biologists.org.

Because the friction between two solid materials is usually related to the force of one of the materials pressing against the other, Ennos and Warman had to find a way of pushing a piece of acrylic glass (Perspex) against Warman's finger before pulling the Perspex along the student's finger to measure the amount of friction between the two. Ennos designed a system that could produce forces ranging from a gentle touch to a tight grip, and then Warman strapped his index finger into the machine to begin measuring his fingerprint's friction.

But after days of dragging the Perspex along Warman's fingers and thumbs, it was clear that something wasn't quite right. Instead of the friction between each finger and the Perspex increasing in proportion to the amount that the Perspex pushed against Warman's fingers, it increased by a smaller fraction than Ennos had expected. Ennos realised that instead of behaving like a normal solid, the skin was behaving like rubber, where the friction is proportional to the contact area between the two surfaces.

To check that skin behaves more like rubber than a normal solid, the duo varied the area of each fingerpad that came into contact with the surface by dragging narrow and wide strips of Perspex along Warman's fingerpads. They found that the friction did increase as more of the fingerprint came in contact with the surface, so the skin was behaving just like rubber.

Finally, the friction issue was clinched when Warman measured his fingerprints' surface area. The area of skin in contact with the Perspex was always 33% less than if the fingerpads were smooth resulting in the maximum contact area. Fingerprints definitely don't improve a grip's friction because they reduce our skin's contact with objects that we hold, and even seem to loosen our grip in some circumstances.

So if fingerprints don't tighten our grasp on smooth surfaces, what are they for? Ennos explains that our fingerprints may function in other ways. They might have evolved to grip onto rough surfaces, like tree bark; the ridges may allow our skin to stretch and deform more easily, protecting it from damage; or they may allow water trapped between our finger pads and the surface to drain away and improve surface contact in wet conditions. Other researchers have suggested that the ridges could increase our fingerpads' touch sensitivity. Whatever our fingerprints are for, it seems that the idea that they provide friction for grip is just another urban myth.


'/>"/>

Contact: Kathryn Knight
kathryn@biologists.com
44-122-342-5525
The Company of Biologists
Source:Eurekalert

Related biology news :

1. New pollution radar developed to provide unprecedented picture of urban smog
2. A win-win: U-pick pumpkin farms recycle urban leaves
3. The physics of star-forming clouds and the urban environment
4. Urban trees enhance water infiltration
5. Networks of small habitat patches can preserve urban biodiversity
6. UC Riverside scientist to explore how vegetation affects urban heat islands
7. Study: urban black bears live fast, die young
8. UMCES-led research team quantifies nutrient pollution reductions from urban stream restoration
9. Some migratory birds cant find success in urban areas, study finds
10. Influenza vaccine causes weaker immune response for children of rural Gabon than in semi-urban areas
11. Molecular fingerprints point the way to earlier cancer diagnosis and more targeted treatment
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:12/20/2016)... 2016 The rising popularity of mobility ... is stoking significant interest in keyless access systems. ... low energy (BLE), biometrics and near-field communication (NFC) ... of wireless technologies in the automotive industry. This ... access systems opens the market to specialist companies ...
(Date:12/16/2016)... Research and Markets has announced the addition ... to 2021" report to their offering. ... The biometric vehicle access system market, ... of 14.06% from 2016 to 2021. The market is estimated to ... 854.8 Million by 2021. The growth of the biometric vehicle access ...
(Date:12/15/2016)... ... has announced the addition of the "Global Military Biometrics Market 2016-2020" ... global military biometrics market to grow at a CAGR of 7.5% during ... on an in-depth market analysis with inputs from industry experts. The report ... The report also includes a discussion of the key vendors operating in ...
Breaking Biology News(10 mins):
(Date:1/19/2017)... , Jan. 18, 2017 The ... reach USD 92.9 billion by 2025, according to ... Pharmaceutical industry has been adaptive of the function ... early as 2002. Among the services outsourced, clinical ... For instance, Johnson & Johnson was the first ...
(Date:1/19/2017)... LAKES, N.J. , Jan. 18, 2017 BD (Becton, ... technology company, announced today that it will host a live webcast ... at 1 p.m. (ET). The webcast can be ... be available for replay through Tuesday, January 31, 2017. ... About BD BD ...
(Date:1/18/2017)... Jan. 18, 2017   Boston Biomedical , an ... to target cancer stemness pathways, will feature data from ... at the 2017 ASCO Gastrointestinal Cancers Symposium, held from ... Napabucasin is an orally-administered investigational agent ... i Cancer stem cells (CSCs) possess the property ...
(Date:1/18/2017)... ... January 18, 2017 , ... Executive search firm Slone Partners ... commitment to the advancement of the clinical trials segment. Hosted in Miami, this ... trial planning and management. , As executive talent specialists in the industries ...
Breaking Biology Technology: