Recharging your devices at your fingertips

INA – SOURCES  
 
A new wearable device turns the touch of a finger into a source of power for small electronics and sensors. Engineers at the University of California San Diego developed a thin, flexible strip that can be worn on a fingertip and generate small amounts of electricity when a person's finger sweats or presses on it.
 
What's special about this sweat-fueled device is that it generates power even while the wearer is asleep or sitting still. This is potentially a big deal for the field of wearables because researchers have now figured out how to harness the energy that can be extracted from human sweat even when a person is not moving.
 
This type of device is the first of its kind, said co-first author Lu Yin, a nano engineering Ph.D. student at the UC San Diego Jacobs School of Engineering. "Unlike other sweat-powered wearables, this one requires no exercise, no physical input from the wearer in order to be useful. This work is a step forward to making wearables more practical, convenient and accessible for the everyday person."
 
The device also generates extra power from light finger presses--so activities such as typing, texting, playing the piano or tapping in Morse code can also become sources of energy.
 
"We envision that this can be used in any daily activity involving touch, things that a person would normally do anyway while at work, at home, while watching TV or eating," said Joseph Wang, a professor of nano engineering at the UC San Diego Jacobs School of Engineering and the study's senior author. "The goal is that this wearable will naturally work for you and you don't even have to think about it."
 
The device derives most of its power from sweat produced by the fingertips, which are 24-hour factories of perspiration. It's a little-known fact that the fingertips are one of the sweatiest spots on the body; each one is packed with over a thousand sweat glands and can produce between 100 to 1000 times more sweat than most other areas on the body.
 
"The reason we feel sweatier on other parts of the body is because those spots are not well ventilated," said Yin. "By contrast, the fingertips are always exposed to air, so the sweat evaporates as it comes out. So rather than letting it evaporate, we use our device to collect this sweat, and it can generate a significant amount of energy."