Researchers at the University of Massachusetts Amherst recently announced that they have developed a biofilm that harvests evaporation energy and converts it to electricity. This biofilm, described in Nature Communications, has the potential to revolutionize the world of wearable electronics by powering everything from personal medical sensors to personal electronics.
“This is a very exciting technology,” says Xiaomeng Liu, the paper’s lead author and a graduate student in electrical and computer engineering at UMass Amherst’s College of Engineering. “It is true green energy, and unlike other ‘green-energy’ sources, its production is completely green.”
This is due to the fact that this biofilm, which is a thin sheet of bacterial cells about the thickness of a sheet of paper, is produced naturally by an engineered version of the bacteria Geobacter sulfurreducens. G. sulfurreducens is known to produce electricity and has previously been used to power electrical devices in “microbial batteries.” However, such batteries necessitate the proper care and feeding of G. sulfurreducens. In contrast, because it is dead, this new biofilm, which can supply as much, if not more, energy than a comparable sized battery, works and works continuously. It also doesn’t need to be fed because it’s dead.
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. This cuts the energy inputs, makes everything simpler and widens the potential applications.
Derek Lovley
“It’s much more efficient,” says Derek Lovley, Distinguished Professor of Microbiology at UMass Amherst and one of the paper’s senior authors. “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. This cuts the energy inputs, makes everything simpler and widens the potential applications.”
The key to this new biofilm’s success is that it generates energy from the moisture on your skin. Despite the fact that we hear about solar power on a daily basis, at least 50% of the solar energy that reaches the earth is used to evaporate water. “This is a massive, untapped source of energy,” says Jun Yao, a UMass professor of electrical and computer engineering and the paper’s other senior author. Because the surface of our skin is constantly wet with sweat, the biofilm can “plug in” and convert the evaporation energy into enough energy to power small devices.
“The limiting factor of wearable electronics,” says Yao, “has always been the power supply. Batteries run down and have to be changed or charged. They are also bulky, heavy, and uncomfortable.” But a clear, small, thin flexible biofilm that produces a continuous and steady supply of electricity and which can be worn, like a Band-Aid, as a patch applied directly to the skin, solves all these problems.
What makes this all work is that G. sulfurreducens grows in colonies that look like thin mats, and each of the individual microbes connects to its neighbors through a series of natural nanowires. The team then harvests these mats and uses a laser to etch small circuits into the films. 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.
“Our next step is to increase the size of our films to power more sophisticated skin-wearable electronics,” Yao says, adding that one of the goals is to power entire electronic systems rather than individual devices.
The Institute for Applied Life Sciences (IALS) at UMass Amherst fostered this research, which combines deep and interdisciplinary expertise from 29 departments to translate fundamental research into innovations that benefit human health and well-being.
