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We Can Hold on to Glass Thanks to Sweat

Although it may seem small, our very fingerstips have evolved to be better. Our fingers have ridges to allow for a better grip on rough surfaces like wood and cloth. These ridges are not designed to increase the grip on something more smooth. This is where the sweat glands come to play. The sweat glands shown in the video produce sweat roughly 20 seconds after your skin comes into contact with a glass surface. This sweat softens the keratin in the skin and allows for the ridges that make up your fingerprint to flatten out. This allows for a better grip on the smooth glass surface. The research done on this included a glass prism and a camera which allowed for the researchers to actually see the sweat being produced. When tested with rubber, the production of sweat was so quick that it could not be seen on camera. All of this has to do with friction and how our body uses friction for our benefit. The formula for friction at the bottom includes the value μk which represents the amount of friction between two objects depending on their texture. For instance, the value for μk would be greater if it was between two two rough objects than if it was between two smooth ones. This analysis of the fingers has practical applications to technology and prosthetics. If scientists know how our fingers react to glass, they could improve the touchscreen experience for smartphone users. In addition, knowing this can improve the capabilities of prosthetic arms while making prosthetics more and more human-like. 
​k

F​k​​=μ​k​​F​n​​

The friction coefficient μk is helpful in understanding the amount of friction between two given objects. The higher the number, the more friction there is between two objects. Some objects that are expected to be slippery like ice sliding on ice do in fact have a low friction coefficient. The coefficient for ice on ice is the low number of 0.02-0.09. On the other hand, two objects with an expected high friction is rubber with rubber. This has a friction coefficient of 1.16. Despite these being somewhat obvious, other friction coefficients are less obvious such as silver with silver. These two substance sliding would seem to be an easy glide, but these have a high coefficient of 1.4. With this in mind, it can be concluded that the friction between skin and glass is increased with the recreation of sweat making the skin less rough. 


http://blogs.discovermagazine.com/d-brief/2017/09/25/sweat-enhanced-grip/#.We5Qoa3MyRs

https://www.khanacademy.org/science/physics/forces-newtons-laws/inclined-planes-friction/a/what-is-friction

http://www.pnas.org/content/114/41/10864.full

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