Scientists at Lawrence Berkeley National Laboratory have been responsible for many discoveries over the years, but this February they published a piece that I found particularly fascinating. Seung-Wuk Lee and his coworkers have created a device that uses a single layer of viruses to generate enough electric current to run small, simple devices (like screens or sensors.) This breakthrough is exciting not only because of the device itself, but also because of its implications for the cost and environmental impact of future generations of widely adopted technologies.
This layer functions based on a principle called piezoelectricity. Piezoelectric materials are special because of their ability to convert pressure into a voltage, and vice-versa. All molecules are made up of positively charge nuclei surrounded by a cloud of negatively charged electrons. This means that certain areas of any given molecule may be generally more positive or more negative.
Now, if pressure is placed on the molecule, it will deform and change shape. In some molecules, this means that the overall distribution of positive and negative charges changes significantly; this movement of electrons around their nuclei, a bit like the electrons moving in a battery, and result in current and voltage. This is only half of the magic of piezoelectric materials, though. The reverse of this “power generation” application also works—that is, if a voltage is applied to a piezoelectric material, it will change size. This has allowed for highly sensitive adjustments—in fact, the finest direct measurements ever made have been accomplished with this approach. More generally
The earliest piezoelectric materials (and the most widely-adopted) were inorganic crystals, but these have the disadvantage of often being expensive or toxic to handle when manufacturing. Still, a host of modern scientific techniques and technologies could not exist without piezoelectricity. The phenomenon was first discovered at the end of the 19th century, and was integral to the development of the first sonar devices during World War I. In the present, technologies including atomic force microscopes, loudspeakers, and even inkjet printers all take advantage of the piezoelectric effect.
This work is not the first time that piezoelectric materials have been developed from organic-based systems. A variety of materials, including collagen fibrils (that form the structure of skin) and even bone, have worked. However, the work from LBNL, based upon harmless viruses, is particularly relevant for actual technology applications. Compared to other protein-based piezomaterials, viruses can be very easily produced by current biotechnological techniques. Beyond the production of the viruses themselves, they have to be coated onto a surface so that the individual effects of a single virus under pressure can be amplified by trillions of other viruses aimed in the same direction. In the case of the viruses in this particular experiment, the M13 bacteriophage, they exhibit self-assembly; this means that even if the viruses are initially disordered on the surface, they will quickly form up into a highly-ordered structure that works perfectly for device manufacture.
In the future, piezoelectric systems would work perfectly as “personal generators” for electronics integrated into clothing and personal technology. It will be exciting to follow the progress of the team at LBNL as they investigate future developments of this approach.