Nearly all our electricity comes from mechanical energy; a flow of liquid or gas passes a propeller or similar device, which spins magnets in a coil of wire to produce an electrical current. This is the basic technology behind hydroelectric, coal, gas, nuclear, and even wind power generation. What if we could harness the power of very tiny flows, such as blood passing through arteries in the body?

That’s the concept behind the work of a team of scientists from Fudan University in Shanghai, China. They have come up with a way to use nanomaterials to harvest energy from blood flow. They have created a thin filament that is less than a millimeter in diameter. Instead of using a mechanical device, such as a propeller, the system relies on the flow of salt solution past the fiber. They started with a plastic core and then wrapped it with carbon nanotubes (CNTs) to create what they call a “fiber-shaped fluidic nanogenerator” (FFNG). The relative motion of the fiber and the solution creates an asymmetrical electrical charge; when connected to electrodes, the fiber produces a current.

The system has been shown to have a power conversion efficiency greater than 20%, which is much higher than other miniature energy harvesting devices. The fiber is small and flexible, and could be woven into textiles that could be suspended in ocean currents to generate power. One intriguing application, however, is to draw energy from a person’s bloodstream. This could provide a continuous source of electricity for devices implanted deep within the body, which would make it more difficult to apply energy from external sources. The FFNG technology could lead to bionic implants that would last a lifetime.