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Wearable electronics are becoming more and more commonplace, driving the need for more durable and more energy-efficient technologies. One persisting limitation for these gadgets, however, is the need to charge them - and new technology could soon overcome this restriction.

According to the Korea Institute of Science and Technology (KIST), a research team led by Director Jin-Sang Kim from the Jeonbuk Institute of Advanced Composite Materials was able to develop a "high-efficiency flexible thermoelectric device" capable of autonomously capable of generating a part of the electricity it needs to run from the wearer's body heat.

The Korean research team published their findings in the report titled "Porous organic filler for high efficiency of flexible thermoelectric generator" appearing in the latest Nano Energy journal.

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Thermoelectric Generators in Wearable Electronics

The new device that could revolutionize wearables electronics features improved thermal insulation characteristics that were achieved by fabricating flexible silicone compounds (Polydimethylsiloxane, or PDMS) into a porous, sponge-like configuration. It is then used as the framework to enhance the device's performance.

It will serve as a new type of thermoelectric generator. Thermoelectric devices are those that generate electricity from the temperature difference, often from two different ends of a device - a cold side and a hot side. The use of the thermoelectric effect for energy generation has been tapped as a more environmentally friendly source of alternative power, as well as a means of utilizing heat as a byproduct of other processes such as those from vehicle engines or from power plants.

On the other hand, applying electricity to thermoelectric devices allows it to use one end for cooling and the other for heating, leading to its use in temperature control systems such as refrigerators, cooling sheets, and semiconductors in electronics.

While existing conventional thermoelectric devices often use a rigid ceramic substrate to support the conducting semiconductor surface, this rigidity makes it difficult to apply these devices on curved or uneven surfaces. Meanwhile, flexible thermoelectric devices contain the thermoelectric semiconductor instead of installing it on a ceramic substrate, making the resulting device more flexible and be bent easier.

In wearable electronics, it allows the autonomous generation of electricity when worn by a user, and it also has the potential as a portable air conditioner. It made flexible thermoelectric devices 

A New Class of Miniature Thermoelectric Generator

While flexible thermoelectric generators are more flexible in their potential applications, most of these materials are not capable of performing at the same level as their more rigid counterparts. To work around this limitation, the Korean research team created a porous sponge-like configuration for the polymer. First, they poured a solution of the silicon compound onto a sugar cube. As the silicon hardened, researchers dissolved the sugar in water, creating gaps in the solidified silicon structure from the dissolved sugar.

The new porous silicon structure was found to offer as much as 50 percent more thermal insulation compared to conventional materials, effectively making it a good material to block heat flow. Researchers used the new substrate material as the support frame for a stable yet flexible thermoelectric device free from usual performance losses.

 

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