Medical Device Link.

Originally Published EMDM November/December 2004

Industry News

Researchers at Imperial College London are working on capacitors that convert energy from body movements. A prototype has been developed.

Advances in medical technology have made it possible for hospital personnel to be notified of sudden medical emergencies in their early stages, sometimes even before patients themselves are aware of them. But what if the equipment for collecting and transmitting that information were small enough to be implanted in the human body, and able to read individuals’ vital signs at any time or place? Better still, what if the sensors functioned without requiring conscious recharging?

Researchers are exploring the possibility of drawing energy for such devices from the most complicated machine of all: the human body. Eric Yeatman and his colleagues at Imperial College London (UK) are working on small capacitors that convert energy from even slight, irregular body movements into electricity that can power medical sensor nodes.

One problem with using batteries to power such sensors is that batteries would require periodic recharging, a variable that developers want to eliminate. “The idea is to replace batteries in very powerful, ultraminiature devices,” says Yeatman. His team’s efforts are part of a larger field of microelectromechanical systems (MEMS), which integrate multiple technologies on a common silicon substrate.

The prototype of the capacitor developed by the Imperial College team uses two electrically charged metal plates, one fixed and the other able to shunt back and forth. Since the plates tend to attract one another, forcing them apart generates electricity. A minimal voltage initially charges up the plates, and the voltage is subsequently amplified with each movement of the mobile plate.

Research on body-implanted sensor nodes takes an innovative approach to an established form of electricity generation: energy harvesting, examples of which include solar power and self-winding watches. “We wanted to look at using motion, like the movement of the body or the movement of internal organs, to provide energy for very small devices,” says Yeatman. Devices may eventually be capable of storing excess energy from periods of intense movement and using it to power a sensor during low points, such as when the user is sleeping.

Though Yeatman stresses that the technology will not be ready for the market for years to come, the prototype marks a noteworthy step forward in this field. Its plates currently measure just 1 cm2 and the entire generator is approximately 1 mm thick. The prototype’s developers look forward to even smaller proportions.

A viable final product could collect medical information, convert it into a communicable signal, and transmit the signal to trained medical staff. In this technology’s ongoing development, according to Yeatman, integration is a key factor in creating a device both effective and convenient. “Ideally,” he notes, “you’d like to put all of those functions on one chip, because that would make [the device] easier, smaller, and more readily useful in the body.”

For more information, contact Eric Yeatman, Department of Electrical and Electronic Engineering, Imperial College London, London SW7 2BT, UK; e-mail: e.yeatman@imperial.ac.uk.


Copyright ©2004 European Medical Device Manufacturer