It should stand to reason that as electronic devices become smaller, so too should the sources that provide their power.
Less than a generation ago, computers were unwieldy behemoths that took up an entire room. Likewise, calculators and telephones have evolved from large boxes to tiny contraptions that slip into a shirt pocket with barely a wrinkle. Now, nanotechnology has taken the concept of downsizing to a whole new level.
In March, a team of scientists at MIT reported the discovery of a new way to generate electricity that would go undetected even to the microscopically aided eye.
The phenomenon, described as thermopower waves, was discovered in experiments with carbon nanotubes that were coated with a layer of a reactive fuel. The fuel was ignited at one end of the nanotube using either a laser beam or a high-voltage spark. Heat from the fuel goes into the nanotube, where it travels thousands of times faster than in the fuel itself. As the heat feeds back to the fuel coating, a thermal wave is created that is guided along the nanotube. With a temperature of 3,000 kelvins, this ring of heat speeds along the tube 10,000 times faster than the normal spread of the chemical reaction. More importantly, the heating produced by that combustion also pushes electrons along the tube, creating a substantial electrical current.
This process “opens up a new area of energy research, which is rare,” said Michael Strano, an associate professor of chemical engineering at MIT, who authored the paper along with Wonjoon Choi, a doctoral student in mechanical engineering.
After further development, the system now puts out energy, in proportion to its weight, about 100 times greater than an equivalent weight of lithium-ion battery.
It may be too soon to tell the practical applications of this new source of power, but Strano suggests one possible application would be in enabling new kinds of ultra-small electronic devices the size of grains of rice or treatment devices that could be injected into the body. While the individual nanowires are tiny, he also suggests that they could be made into large arrays to supply significant amounts of power for larger devices.