TOMORROWS CELL PHONE

Making calls from a cell phone without a battery, using just the
Warmth of your hand? Perhaps that's no more than a pipe dream right
now. But new circuits being developed by researchers in Germany are
already making it possible to harness body heat for generating
electricity.

Numerous items of medical equipment are attached to a patient's body
in the intensive care ward. They monitor the heart rate, blood
pressure, body temperature, pulse and breathing rate. This tends to
produce quite a jumble of cables as all these devices require their
own electricity supply.

In future, medical sensors may be able to function without power from
a wall socket. Instead, they will draw all the power they need from
the warmth of the human body, say the German researchers. The data
will be sent by a radio signal to the central monitoring station.

Research scientists at the Fraunhofer Institute for Integrated
Circuits IIS in Erlanger, Germany, have developed a way of harnessing
natural body heat to generate electricity.

It works on the principle of thermoelectric generators, TEG for short,
made from semiconductor elements. The TEGs extract electrical energy
simply from the temperature difference between a hot and a cold
environment.

Normally, a difference of several tens of degrees would be required to
generate enough power, but the differences between the body's surface
temperature and that of its environment are only a few degrees.

A conventional TEG delivers roughly 200 millivolts, but electronic
devices require at least one or two volts. The engineers have come up with a solution to this problem: "They combined a number of components in a completely new way to create circuits that can operate on 200 millivolts,".

"This has enabled us to build entire electronic systems that do not
require an internal battery, but draw their energy from body heat
alone." The scientists are making further improvements to this system: