Tech

A wireless antenna that channels signals along human skin could broadcast signals over your body to connect up medical implants or portable gadgets.

The new power-efficient approach could make more of established medical devices like pacemakers or help future implants distributed around the body work together.

Just one of the small hockey-puck-like antennas developed at Queen's University Belfast, Northern Ireland, would be able to connect to gadgets anywhere else on the body, says William Scanlon who made the design with colleague Gareth Conway.

The new design's ability to produce signals that creep along the skin makes it more efficient than existing battery-hungry technologies such as Bluetooth, says Scanlon - an important factor for medical devices which need long life-spans.

Signal stopper

Compact "patch" antennas that lie flat on the skin have been made before. But they make poor connectors because most of their signals travel away from the body, not along it.

Mast-style 'monopole' antennas like those on cars are better at transmitting laterally. But still transmit upwards too.

Now, Scanlon and Conway have designed a version that that channels much more of its signal sideways by taking advantage of the "creeping wave" effect that allows waves to travel along a surface. The same effect is responsible for both a person's ears hearing a sound only directed at one side of their head.

Flipped mast

Monopole antennas stand on a plate of conductive material - like a car roof - to reflect signals travelling downwards. But Scanlon and Conway have shown that turning the design upside down, putting the plate on top of the antenna and away from the body, helps channel signals along the skin.

"There is a mismatch between the air and the body tissue, which causes a reflection of sorts," says Scanlon.

Signals are channelled out sideways along the skin by this reflection and the conducting plate. That makes the antenna more efficient, which could double the battery life of body-worn gadgets, Scanlon says.

"The idea of inverting the antenna to encourage surface wave propagation around the body is worth patenting," John Batchelor, University of Kent, who is working on similar devices.

Scanlon and Conway have applied for a patent for their new antenna.

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