The M13 virus is basically a single strand of DNA 880nm long and 6.6nm in diameter, with a coat of 2,700 charged proteins, “and large numbers of the rod-shaped viruses naturally orient themselves into well-ordered films, much the way that chopsticks align themselves in a box”, said the Berkeley Lab, where the work was done.
Already identified as piezoelectric because the helical proteins twist the microbe in an electric field, genetic engineering was used to boost the effect.
Four negatively charged amino acid residues were added to one end of the protein to increase the charge difference between its positive and negative ends.
The researchers “created the conditions for the genetically engineered viruses to spontaneously organise into a multilayered film that measures about one square centimetre”, said the lab. “This film was then sandwiched between two gold-plated electrodes, which were connected by wires to a liquid-crystal display.”
With around 20 layers, finger pressure generated 6nA at 400mV – enough to change the state of two segments of the LCD to display a ‘1’.
“More research is needed, but our work is a promising first step toward the development of personal power generators, actuators for use in nano-devices, and other devices based on viral electronics,” claimed scientist Dr Seung-Wuk Lee.
A paper, ‘Virus-based piezoelectric energy generation‘, appeared as an advance on-line publication on Nature Nanotechnology’s website.
M13 is a bacteriophage, a virus that attacks bacteria.
In research it has been engineered to make aligned carbon nanotubes for photocells, and to assemble cobalt oxide nanowires from lithium ion batteries.
Certain bacteriophages have been used to treat bacterial infections, and are now being investigated as alternatives to antibiotics.