Some bacteria are known to produce their own electricity, which could make them useful in making up batteries and fuel cells. Until yesterday, however, the attempts had been inefficient and inflexible.
Today, good news in the field of innovative batteries. Researchers from the Karlsruhe Institute of Technology (KIT) have created a 'biohybrid' structure built around a hydrogel that can support microbes while efficiently harvesting their energy. The bacteria at the center of this system are known as exoelectrogenic bacteria: this family of microbes can produce electrons, transfer them across their outer membrane and thus away from their cell. If we can capture these electrons, exoelectrogenic bacteria can essentially help build a living battery.
But there is a delicate balance, and evidently previous attempts had failed to respect it. Conductive materials are needed to deflect electrons on an electrode, but most of these are not ideal for bacteria survival. Those who are more welcoming to life, on the other hand, are not efficient conductors. In summary: if there was a good conductor, it killed bacteria and therefore no energy. No living battery. If the conductor was not good, the bacteria remained alive but not enough energy was produced.
The new study for the living battery
For the new study, the researchers developed their own material that aimed to solve this impasse and save "goat and cabbage", or rather "conductor and bacteria". It consists of a hydrogel made of carbon nanotubes and silica nanoparticles, which conduct electricity. All of this is held together by strands of DNA. Exoelectrogenic bacteria are then added to this infrastructure along with a nutrient-rich culture medium to keep them alive.
The researchers say the recipe could be modified to modify some properties of the material, in particular by changing the size and sequences of the DNA strands.
The team found that the bacteria grew well on the material, penetrating deep into the hydrogel's pores. The hydrogel also did a good job of conducting electricity. The researchers also built a way to turn off the battery. When energy is no longer needed, an enzyme can be added that "cuts" the DNA strands and collapses the material.
The research was published in the journal ACS Applied Materials & Interfaces .
Photos: American Chemical Society