By TINA CASEY
Researchers are finding new sources of clean energy in the strangest places. In the latest development, a team at the Lawrence Berkeley National Laboratory has engineered a tiny device coated with viruses that generate electricity when stimulated by the touch of a finger.
The postage stamp-sized device could lead to the development of a new class of “viral electronics” that run on clean energy harvested from the everyday movements of people such as walking across a floor or opening doors.
The device is based on the principles of piezoelectricity, which refers to the ability of certain materials to generate electricity when put under stress.
Piezoelectricity was discovered in the 1880’s and is used to strike a spark in ordinary devices like electric cigarette lighters, microphones and quartz watches. It also has applications in high tech fields including scanning microscopy.
Until recently, crystal and ceramic materials have been the foundation of piezoelectric devices, but biological materials including bone, protein and DNA are starting to join the mix.
New research is also leading to a new class of flexible applications. In the U.K., a team at the University of Bolton is developing a lightweight, flexible piezoelectric fiber that could be woven into a fabric. The fabric could generate an electric charge from a wide variety of forces including wind, rain, and human activity.
One factor that is enabling the piezoelectric field to expand is the development of safe substitutes for lead and other toxic materials that are used in conventional piezoelectric devices.
The virus-powered device is based on the M13 bacteriaophage, which attacks bacteria but is harmless to humans.
As a “building block” for fabricating low cost electronic devices, M13 dovetails perfectly with the nanotechnology concept of self-assembly. It replicates itself rapidly, and it naturally aligns into an orderly film, similar to the way that toothpicks pack into a box.
The first step of the research involved searching for signs of a piezoelectric effect, which the team observed by coating helical proteins (proteins that curve in three dimensions) over M13 viruses and exposing them to an electrical field.
To increase the voltage, they added amino acid residues to one end of the proteins, which increased the difference between the positive and negative ends.
Adding even more punch, the team coaxed the viruses into self-assembling into a multilayered film about one centimeter square. With gold-plated electrodes placed on each side to form a micro-sandwich, the piezoelectric generator was complete.
The initial tests yielded about a quarter the voltage of an AAA battery, which was sufficient to make an attached liquid-crystal display flash the number “1.
Scaled up, such a device could be built into a shoe insert, for example, and used to power cell phones and other mobile devices.
With a low cost, non-toxic foundational material at hand, shoe inserts could be just the tip of the piezoelectric iceberg, and opportunities for piezoelectric energy harvesting are already broadening into large-scale applications as the research field matures.
Things began to heat up in 2008, when a Dutch nightclub made waves with a piezoelectric floor that harvested energy from late-night dancers and the East Japan Railway Company announced that it would test a piezoelectric floor at a Tokyo railway station.
A few years ago, the U.S. company New Energy Technologies began testing piezoelectric harvesters installed as speed bumps in the drive-through lanes at Burger King in New Jersey, and just last year it debuted a full scale version of the system at a convention center in Virginia.
In addition to the virus research, a team at Berkeley has also been developing a new lead-free piezoelectric material based on thin films of an inorganic crystalline material called bismuth ferrite, which is commonly used in cosmetics and pharmaceuticals. Bismuth ferrite is just one member of a class of non-toxic materials that exhibit magnetic-electric phenomena and have a potential use in large-scale piezoelectric devices.
For those of you dreaming of an entire electric highway, you might not have long to wait. Last year, California Assemblyman Mike Gatto introduced a bill authorizing the state to embark on a research and development project similar to ones already under way in Italy and Israel.
