The existing antimicrobial water filters have a serious drawback - over time, those bacteria that could not penetrate through its membrane settle on it and accumulate. If such a filter is thrown into a landfill, it will still remain a source of hazardous contamination. Scientists at the University of Washington in St. Louis found an elegant solution to this problem - and used the bacteria themselves to do this.
The role of unintentional traitors was played by microorganisms of the type Gluconacetobacter hansenii, which, when absorbed by sugar substitutes, produce cellulose nanofibers. They became the basis for a new membrane, on which graphene particles were deposited to make it durable. This design turned out to be stronger and more resistant to aggressive media than analogs obtained by centrifugation of graphene oxide or vacuum filtration.
The scientists liked that the bacteria Gluconacetobacter hansenii could be fed different types of carbohydrates and thereby influence the quality of the resulting membrane. When it was ready, the traitor microbes were destroyed in boiling water, and the graphene was reduced with oxygen. He gained the ability to react to sunlight and heat the membrane to high temperatures.
In the course of the experiment, the membrane illuminated by the sun is passively heated to 70 ° C in 3 minutes, which is enough to destroy the E. coli deposited on it. Bacteria cease to accumulate on the surface of the membrane, and its permeability increases. It is expected that this development will form the basis of low-cost household filters for developing countries. In theory, they can even become a source of heat and electricity if water heated by graphene is immediately supplied to microgenerators.