Nanotube Yarn

Harvesting energy from motion within the environment has met with limited success except in applications where there are high levels of vibration, such as mounted on a high-traffic bridge or railroad trestle. Known as piezoelectric sensors, these systems transform mechanical strain into electrical current that can be used to power relatively low-power devices. The same principle has been applied to sensors that harvest energy from movement of the human body to power things like watches.

One area in which harvesters would be extremely useful is in ocean-based, pollution-sensing buoys. The continual need for battery power often limits their practicality, and ocean waves simply do not supply enough energy for typical piezoelectric sensors to function efficiently. But researchers recently developed a new device called a “twistron harvester” that generates power at higher levels than any other harvesters to date.

The key is a twisted “yarn” made of carbon nanotubes and spun into a coil approximately one-twentieth of a millimeter in diameter. When submerged in an electrolyte, it generates enough energy to power a sensor from wave motion alone. Other applications could include sewing the yarn into a shirt to monitor respiration. The fibers are also capable of converting thermal energy into power, and the performance is scalable—that is, the larger the diameter, the more power they can generate. The next hurdle is to decrease the cost to the point where “twistrons” are commercially viable.