Producing Electricity from Your Sweat
By William Huang
Today, climate change is constantly in the news. From rising global temperatures to increases in natural disasters, we are constantly reminded of the detrimental effects of greenhouse gasses. As the global temperature shifts, so will the need for energy? But what does that exactly mean? Demands for cooling may grow as summer heat waves arrive. In addition,renewable energy sources like hydropower may be affected, temperatures increase the demand for cooling in the summer and heating in the winter. Therefore, energy is extremely valuable, and scientists are exploring many possible avenues today to harness it. One recent study leverages the almost 8 billion people on Earth.
Biofilms, thin sheets of bacterial cells about the thickness of a sheet of paper, are produced naturally by an engineered version of the bacteria
Geobacter sulfurreducens.
G. sulfurreducens is known to produce electricity and has been used previously in "microbial batteries" to power electrical devices. But such batteries require that
G. sulfurreducens are properly cared for and fed a constant diet. By contrast, a new biofilm produced by the University of Massachusetts Amherst can supply as much energy as a comparably sized battery, and doesn't need to be fed.
The biofilms are much more efficient, and simpler because the bacteria generating electricity cuts back on the amount of processing needed. They sustainably grow the cells in a biofilm, and then use that agglomeration of cells. With this process, they cut the energy input, making the overall process simpler.
The secret behind this new biofilm is that it makes energy from the moisture on your skin. Though we daily read stories about solar power, at least 50% of the solar energy reaching the earth goes toward evaporating water. Because it is a huge source of untapped energy, professors believed that since the surface of our skin is constantly moist with sweat, the biofilm can "plug-in" and convert the energy locked in evaporation into enough energy to power small devices.
One limiting factor of wearable electronics is the power supply. Batteries run down and have to be changed or charged. They are also often uncomfortable and bulky. But a clear, small, thin flexible biofilm that produces a continuous and steady supply of electricity and can conveniently be worn like a Band-Aid 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 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.
Their next step is to increase the size of the films to power more complicated skin-wearable electronics, with the hopes that one day, they can power entire electronic systems, rather than single devices.
Citations:
https://www.nature.com/articles/s41467-022-32105-6
https://www.sciencedaily.com/releases/2022/08/220802153311.htm
Image Credit:
https://ganamod.com/news/biofilm-that-generates-electricity/
