A hybrid system of bacteria and nanowires (a kind of cyborg or biohybrid bacteria) that capture energy from sunlight and transfer it to bacteria to convert carbon dioxide and water into organic molecules and oxygen has been developed by chemical researchers from the University of California Berkeley and the Lawrence Berkeley National Laboratory.
The efficiency is higher than the photosynthetic efficiency of most plants.
One system for Earth and Mars
This system could be useful both for Earth (it could remove carbon dioxide from the atmosphere) and for Mars (it would provide colonists with raw materials to make organic compounds ranging from fuel to medicine). As the project leader Peidong Yang explains :
Mars, about 96% of the atmosphere is CO2. Basically all you need is these silicon semiconductor nanowires to absorb solar energy and pass it on to these insects to do the chemistry. For a mission in deep space, the weight of the payload is important, and biological systems have the advantage of self-replicating: you don’t need to send much. That is why our biohybrid version is so attractive.
We are therefore facing a milestone in the packaging of these bacteria ( Sporomusa ovata ) in a "nanowire forest" to achieve record efficiency: 3.6% of incoming solar energy is converted . It is comparable to the plant that best converts CO2 into sugar: sugar cane, which has an efficiency of 4-5%.
Nanowires are thin strands of silicon about one hundredth the width of a human hair, used as electronic components, and also as sensors and solar cells, but in this particular experiment, the nanowires were used only as conductive wires, not as solar absorbers. An external solar panel provided the power .
The system works like photosynthesis that plants use naturally to convert carbon dioxide and water into carbon compounds. The difference is that a two-carbon molecule called acetate is produced here : essentially acetic acid or vinegar. Acetate molecules can serve as building blocks for a variety of organic molecules, from fuels and plastics to medicines.
For now, the researchers continue to look for ways to increase the efficiency of the biohybrid, and are also exploring techniques to genetically engineer the bacteria to be more versatile.