It is the dream of many: to have a renewable energy source available, free or almost, without ever interrupting one’s supply. What if we were ourselves to produce it to power our cell phone, we could make ourselves independent from power banks and electrical sockets and also from fossil fuels. A group of researchers from the Electrical Computer and Engineering Department of the University of Massachusetts managed to achieve this result. They have developed a dermal patch that produces electricity from our sweat. They started with a consideration: about 50 percent of the solar energy that reaches our planet causes water evaporation, a process that removes heat from the external environment. This change of state according to many experts it could be used to produce electricity cleanly. However, not all materials used in the experiments developed so far are produced in a sustainable way and often also require large surfaces.
Instead, scientists have shown that it is It is possible to obtain adhesive and flexible biofilms by engineering some bacteria that allow a continuous production of energy that can be used for example for the telephoneor for one glucose sensor of those worn by diabetics.
Microorganisms are widespread everywhere, there are millions of species. Many are able to generate electricity starting from the oxidation of organic matter, but some are also able to do so by exploiting the evaporation of water. One of these is the Geobacter sulfurreducens which works even when it is no longer alive, so it does not need to be fed and it is not necessary to take care of it. It is raised in colonies as thick as a sheet of paper, in which the various individuals are connected to each other via nanowires. Using the laser they were used as a matrix in which to thread a circuit.
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The whole is then placed in a breathable polymer patch that can be used for produce electricity from sweat or moisture on the skin even when we don’t sweat.
Just 40 microns thin, it produces 1 micro Watt per square centimeter, much more than other thicker materials. And lasts about 18 hours. What you need for a whole working day, and even more. The system is much more efficient than the other wearable generators available at the moment. Some use the heat, others the movement. However, they need to be recharged from time to time and their portability is not always ideal. Evaporation through the biofilm, on the other hand, also has the characteristic of being much faster than that which could occur on a generic surface of water.
In the case of the patch, interruptions cannot occur because our skin is constantly covered with a veil of sweat and the film does not need activators.
On very hot days we can sweat even more than 2 liters per hour, until we lose 10-12 liters of water a day because we have between 2 and 4 million sweat glands. If you do sports, the value goes up. In short, the biofilm never fails to have the raw material it needs.
The next goal of the researchers is to increase the size of the patch to power larger electrical appliances. It would be interesting to be able to load the computer as well. The invention could also go beyond the confines of wearable devices. If remodeled over large areas, it could serve to achieve the objectives of reducing greenhouse gases for productive and social activities.
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