Generating Electricity with Body Temperature
The Korea Institute of Science and Technology (KIST) announced on March 3 that its research team led by Dr. Kim Jin-sang developed a flexible thermoelectric element capable of semi-permanently generating electricity by using body temperature. The element is characterized by containing polydimethylsiloxane (PDMS) in a sponge form and efficiently blocking heat with the flexible silicone compound and is expected to facilitate the use of various wearable devices such as smart bands by reducing the necessity of charging.
In most thermoelectric elements, a hard ceramic substrate supports a thermoelectric semiconductor. As such, it is not easy to use the elements for a bent or curved part. A flexible thermoelectric element, however, lacks a ceramic substrate and its flexible polymer material surrounds a thermoelectric semiconductor for the element to be easily bendable.
When the element is on the human body, semi-permanent electricity generation is possible along with use as a portable air conditioner. In this regard, this technology has drawn much attention in the field of electronic devices for use on the human body. However, the polymer material as a flexible substrate has a high level of heat conductivity, the heat of the material cannot be blocked and its performance is problematically limited as compared with hard substrate-based thermoelectric elements.
The research team made a sponge-like polymer material by pouring a liquid silicone compound onto sugar cubes, hardening it, and then removing the sugar by melting it in water. As a result, fine air bubbles took the sugar part, the thermal barrier capacity improved by more than 50 percent and heat transfer was effectively blocked. This substrate was used as a frame supporting the thermoelectric element so that its flexibility and performance can be guaranteed at the same time.
The flexible thermoelectric element developed by the team outperforms existing flexible thermoelectric elements by at least 20 percent. The team succeeded in turning on an LED light with body temperature by using its element.
“We boosted the efficiency of flexible thermoelectric elements to the efficiency levels of existing commercial thermoelectric elements simply through the pouring and hardening process, which is very simple and economical,” the team explained, adding, “It is expected that a smart band will be usable with nothing but body temperature if a sufficient number of the thermoelectric elements are used.” Details of the research are available in this month’s edition of the Nano Energy journal.