Engineering 101

Are You a Couch Potato? You Can Still Be Useful

Ever been called a couch potato? Now you have a comeback: “I’m busy creating energy!” A wearable device turns the touch of a finger into a source of power for small electronics and sensors. Engineers at the UC San Diego developed a thin, flexible strip that can be worn on a fingertip to generate small amounts of electricity when a person’s finger sweats or presses on the strip.

It generates power even while the wearer is asleep or sitting still, leaving the wearer additional “nap” options.  Seriously, this is cool. Researchers figured out how to harness energy extracted from human sweat even when a person is still.

Co-first author Lu Yin, a nanoengineering Ph.D. student at the UC San Diego Jacobs School of Engineering claims the innovation is a first as it requires no exercise or physical input from the wearer. The energy harvester is described in a paper published July 13 in Joule.

The device is a thin, flexible strip that can be worn like a Band-Aid. A padding of carbon foam electrodes absorbs sweat and converts it into electrical energy. Electrodes are equipped with enzymes that trigger chemical reactions between lactate and oxygen molecules in sweat to generate electricity. Underneath the electrodes is a chip made of piezoelectric material, which generates additional electrical energy when pressed. When used, electrical energy gets stored in a small capacitor and is discharged to other devices when needed.

The researchers had a subject wear the device on one fingertip while doing sedentary activities. From 10 hours of sleep, the device collected almost 400 millijoules of energy–enough to power an electronic wristwatch for 24 hours. From one hour of casual typing and clicking on a mouse, the device collected almost 30 millijoules.

In other experiments, the researchers connected their energy harvester to an electronic system consisting of a chemical sensor connected to a small low-power display, which shows a numerical reading of the sensor’s data. Either pressing the energy harvester 10 times every 10 seconds or simply wearing it on the fingertip for two minutes was enough to power both the sensor and the display

The team is making further improvements for greater efficiency and durability.. Future studies will include combining it with other types of energy harvesters.

Original Release: Eureka Alert

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