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GEN News Highlights : May 14, 2012

Scientists Create Piezoelectric Generators from Bacteriophage Thin Films

Modified M13 bacteriophages set stage for design of virus-based microelectronics.

Scientists have created bacteriophage-based microelectronic devices that can generate enough electricity to power a liquid-crystal display (LCD) when subjected to mechanical force. The prototype piezoelectric devices are composed of engineered M13 bacteriophages that self-assemble into thin films.

Scientists from the University of California, Berkeley demonstrate the use of the thin films to generate power by layering multiple 1cm2 films between two electrodes and connecting the setup to an LCD. When pressure was repeatedly applied and released, the microgenerator produced up to 6 nA of current and 400 mV of potential, equivalent to about a quarter of the voltage of an AAA battery.

Seung-Wuk Lee, Ph.D., and colleagues say they hope that the proof-of-concept prototype will pave the way to the development of cheap virus-based microelectronic devices that generate power from everyday activities such as shutting doors or climbing stairs. They report their achievement in Nature Nanotechnology in a paper titled “Virus-based piezoelectric energy generation.”

Piezoelectric devices (i.e., those that accumulate a charge in response to an applied mechanical force such as pressure) have already been developed from inorganic and some organic polymers. The concept is integral to devices ranging from electric cigarette lighters to scanning probe microscopes. However, producing these materials can require toxic starting materials and complex or harsh procedures.

It has more recently been shown that biological materials such as bones, collagen, and peptide nanotubes can also display piezoelectric properties. The latest work by Dr. Lee’s team extends these findings to demonstrate the feasibility of generating environmentally friendly piezoelectric devices from viruses that, importantly, will self-assemble into thin films.

The team first used piezoelectric force microscopy to confirm that M13 bacteriophages demonstrate inherent piezoelectric properties. These properties are down to the structure of the viruses and, in particular, their coat proteins. The researchers were then able to optimize the peizoelectric strength of the viruses even further by modifying pVIII coat protein. This was achieved using recombinant DNA techniques to effectively add negatively charged amino acids to one end of the helical pVIII protein and increase the charge difference between the protein’s positive and negative ends, boosting voltage.  “This indicates that our phage-based piezoelectric devices can be scaled up to generate a higher energy output,” the team states.

Encouragingly, when two devices of the same polarity and similar electromechanical response were combined in parallel or in series, the resulting current or voltage, respectively, could be increased even further. “Because biotechnology techniques enable large-scale production of genetically modified phages, phage-based piezoelectric materials potentially offer a simple and environmentally friendly approach to piezoelectric energy generation,” the authors write. “Additional levels of control and optimization may come from exploring different viral particles and their diverse structural proteins.”