Wearable computers and devices are being hailed as the next generation of mobile electronics, from smart watches to smart glasses to smart pacemakers. However, for these devices to be worn by the user, they need to be light, flexible and equipped with a power source.
Their power source could be a long-lasting battery or even a generator in place of a battery. One of the most critical issues to commercializing wearable devices is how to supply power in a stable and reliable manner.
A team of researchers from Korea Advanced Institute of Science and Technology (KAIST), headed by Byung Jin Cho, a professor of electrical engineering, proposed a solution to this problem by developing a glass fabric-based thermoelectric (TE) generator that is extremely light and flexible and produces electricity from the heat of the human body.
In fact, it is so flexible that the allowable bending radius of the generator is as low as 20 mm. There are no changes in performance even if the generator bends upward and downward for up to 120 cycles.
There have been two types of TE generators developed, to date, based on organic or inorganic materials. The organic-based TE generators use polymers that are highly flexible and compatible with human skin, ideal for wearable electronics. The polymers, however, have a low power output. Inorganic-based TE generators produce a high electrical energy, but they are heavy, rigid and bulky.
Professor Cho came up with a new concept and design technique to build a flexible TE generator that maximizes thermal energy loss but maximizes power output. His team synthesized liquid-like pastes of n-type (Bi2Te3) and p-type (Sb2Te3) TE materials and printed them onto a glass fabric by applying a screen printing technique. The pastes permeated through the meshes of the fabric and formed films of TE materials in a range of thickness of several hundreds of microns. As a result, hundreds of TE material dots (in combination of n and p types) were printed and well arranged on a specific area of the glass fabric.
“Our technology presents an easy and simple way of fabricating an extremely flexible, light, and high-performance TE generator. We expect that this technology will find further applications in scale-up systems such as automobiles, factories, aircrafts, and vessels where we see abundant thermal energy being wasted,” stated professor Cho.