Electricity from fungi and bacteria
Bacterial solar panels were printed on mushrooms
Grigory Kopiev, N+1
American researchers have proposed using mushrooms as the basis for biological solar panels that generate electricity thanks to photosensitive cyanobacteria. Experiments with 3D-printed prototypes have shown that fungi increase the survival of bacteria after printing, say the authors of the article in Nano Letters (Joshi et al., Bacterial Nanobionics via 3D Printing).
Scientists have already created quite a lot of variants of such a biological solar panel, but so far they all remain only laboratory prototypes. One of the reasons for this is that the lifetime of bacteria is short for real use due to insufficient biocompatibility of the remaining panel elements, unsuitable conditions or other factors. Manu Mannoor and his colleagues from Stevens University of Technology proposed to increase the lifetime of cyanobacteria in biophotovoltaic devices by using another organism as a substrate — a fungus. Thanks to this carrier, the bacteria get the necessary moisture from the soil through small channels in the fungus. In addition, it provides bacteria with optimal temperature and acidity of the medium.
Layers of hydrogel with bacteria and graphene conducting tracks on a real mushroom and polymer model (drawings from the article in Nano Letters).
In addition to classical technologies for creating solar panels, there is also a less popular direction — biofotovoltaics. It uses bacteria capable of photosynthesis as a converter of sunlight into electric current. As a rule, scientists use cyanobacteria — blue-green algae for this. In the presence of water and light, they split water molecules into molecular oxygen, a hydrogen ion and an electron. This electron can be captured by one electrode, and then used on another electrode to reverse the conversion of oxygen and hydrogen into water.
The researchers created two types of "ink" for printing on a mushroom (in this case, it was a mushroom). One of the materials is based on a sodium alginate hydrogel, which contains a nutrient medium for bacteria and the bacteria of the genus Anabaena themselves. The second printing material is a conductive mixture of two PEDOT:PSS ionomers, to which graphene nanofilms were added. During printing, the 3D printer first creates a current collector from a graphene mixture, and then prints a spiral strip from a mixture with cyanobacteria on top of it.
The survival of bacteria on a real mushroom (green) and an artificial mushroom (red), as well as in the form of separate films from a mixture of two materials.
To test the characteristics of phototrophic bacteria as a solar energy converter, the researchers conducted several experiments. The measurement of electrical characteristics showed that the maximum current generated is about 67 nanoamps, and 3D printing of organized structures increases the amount of current compared to evenly distributed bacteria. In addition, the authors investigated the effect of the fungus on bacterial survival compared to printing on a polysiloxane model of the fungus. It turned out that using a real mushroom as a substrate significantly increases survival compared to using an artificial substrate, but even in this case, the number of live bacteria drops to about ten percent after three days.
Last year, British scientists presented a method that allows using an inkjet printer to print biofotovoltaic panels on paper. The researchers printed several prototypes and were able to use them to power a simple clock with a liquid crystal screen and an LED.
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