by Staff Writers
San Diego CA (SPX) Aug 23, 2017
A team of engineers has developed stretchable fuel cells that extract energy from sweat and are capable of powering electronics, such as LEDs and Bluetooth radios. The biofuel cells generate 10 times more power per surface area than any existing wearable biofuel cells. The devices could be used to power a range of wearable devices.
The epidermal biofuel cells are a major breakthrough in the field, which has been struggling with making the devices that are stretchable enough and powerful enough. Engineers from the University of California San Diego were able to achieve this breakthrough thanks to a combination of clever chemistry, advanced materials and electronic interfaces. This allowed them to build a stretchable electronic foundation by using lithography and by using screen-printing to make 3D carbon nanotube-based cathode and anode arrays.
The biofuel cells are equipped with an enzyme that oxidizes the lactic acid present in human sweat to generate current. This turns the sweat into a source of power.
Engineers report their results in the June issue of Energy and Environmental Science. In the paper, they describe how they connected the biofuel cells to a custom-made circuit board and demonstrated the device was able to power an LED while a person wearing it exercised on a stationary bike.
Professor Joseph Wang, who directs the Center for Wearable Sensors at UC San Diego, led the research, in collaboration with electrical engineering professor and center co-director Patrick Mercier and nanoegnineering professor Sheng Xu, both also at the Jacobs School of Engineering UC San Diego.
Islands and bridges
The basis for the islands and bridges structure was manufactured via lithography and is made of gold. As a second step, researchers used screen printing to deposit layers of biofuel materials on top of the anode and cathode dots.
Increasing energy density
"We needed to figure out the best combination of materials to use and in what ratio to use them," said Amay Bandodkar, one of the paper's first authors, who was then a Ph.D. student in Wang's research group. He is now a postdoctoral researcher at Northwestern University.
To increase power density, engineers screen printed a 3D carbon nanotube structure on top the anodes and cathodes. The structure allows engineers to load each anodic dot with more of the enzyme that reacts to lactic acid and silver oxide at the cathode dots. In addition, the tubes allow easier electron transfer, which improves biofuel cell performance.
Researchers equipped four subjects with the biofuel cell-board combination and had them exercise on a stationary bike. The subjects were able to power a blue LED for about four minutes.
Also, the concentration of lactic acid in a person's sweat gets diluted over time. That is why subjects were able to light up an LED for only four minutes while biking. The team is exploring a way to store the energy produced while the concentration of lactate is high enough and then release it gradually.
Mexico City (AFP) Aug 17, 2017
The prickly pear cactus is such a powerful symbol in Mexico that they put it smack in the middle of the national flag. It was considered sacred by the ancient Aztecs, and modern-day Mexicans eat it, drink it, and even use it in medicines and shampoos. Now scientists have come up with a new use for the bright green plant: producing renewable energy. Instantly recognizable with its jum ... read more
University of California - San Diego
Bio Fuel Technology and Application News
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