Photo: Pixabay/yellowcat

Wearable electronics like personalized fitness trackers and medical sensors are already a part of life for many people and soon they could become even more appealing. That is because scientists in the US have engineered a biofilm that harvests the energy from its wearer’s sweat and converts it to electricity.

The biofilm, which is about as thick as a sheet of paper, is made with a bioengineered version of the bacteria Geobacter sulfurreducens, well known for its capacity to produce electricity.

In previous applications of the bacteria for producing electricity by way of “microbial batteries” to power electrical devices, however, there was a drawback, which was that they needed to be kept alive and fed a constant diet. The new biofilm engineered by a team of researchers at the University of Massachusetts Amherst has done away with that requirement by using dead microbes.

Better yet: the new biofilm battery “can supply as much, if not more, energy than a comparably sized battery,” according to the scientists. “It’s much more efficient,” explains Derek Lovley, a distinguished professor of microbiology at UMass Amherst and one of the senior authors of a paper on the research.

“We’ve simplified the process of generating electricity by radically cutting back on the amount of processing needed. We sustainably grow the cells in a biofilm, and then use that agglomeration of cells,” Loveley says. “This cuts the energy inputs, makes everything simpler and widens the potential applications,” the scientist adds.

The new biofilm generates energy from the perspiration on skin by harvesting evaporating water through a mechanism for creating enough energy to power small electronic devices. “This is a huge, untapped source of energy,” stresses Jun Yao, a professor of electrical and computer engineering at UMass.

“The limiting factor of wearable electronics has always been the power supply. Batteries run down and have to be changed or charged. They are also bulky, heavy, and uncomfortable,” Yao says.

Their solution to that problem involves a clear, thin and flexible biofilm that can be worn like a Band-Aid on the skin so it can produce a steady supply of electricity. That is thanks to G. sulfurreducens bacteria, which grow in colonies that resemble thin mats with each microbe connects to its neighbors through a series of natural nanowires.

The new technology harvests these mats and etches small circuits into the films with a laser. “Once the films are etched, they’re sandwiched between electrodes and finally sealed in a soft, sticky, breathable polymer that you can apply directly to your skin. Once this tiny battery is ‘plugged in by applying it to your body, it can power small devices,” the scientists explain.

“Our next step is to increase the size of our films to power more sophisticated skin-wearable electronics,” Yao says.

In future the biofilm could power entire electronic systems rather than wearable single devices, the scientists note.

“This is a very exciting technology,” says Xiaomeng Liu, a graduate student in electrical and computer engineering at the university’s College of Engineering who helped lead the research. “It is real green energy, and unlike other so-called ‘green-energy’ sources, its production is totally green.”

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