Prof. Sangsig Kim’s team develops nanocrystal thin films that generate electricity using body heat

▲ Prof. Sangsig Kim, School of Electrical Engineering, College of Engineering

A research team led by Professor Sangsig Kim of the School of Electrical Engineering under the College of Engineering succeeded in developing flexible thermoelectric nanocrystal thin films that generate electricity using body heat. The results were published on July 18 under the title “Large Voltage Generation of Flexible Thermoelectric Nanocrystal Thin Films by Finger Contact” in the online version of

Advanced Energy Materials (IF=16.7, top 2.7% in the field of energy).

Thermoelectric modules are recognized as a next-generation source of energy as they convert body heat or industrial waste heat into electricity. They have been utilized in military and aerospace-related fields, but require more extensive integration for use in everyday life. While existing nanomaterial thermoelectric modules consist of micro-sized thin films, the nanocrystal thermoelectric modules developed by Prof. Kim’s team have a thickness in nano units and length and width in micro units. The team fabricated a nanocrystal thin film thermoelectric module with a 40pn array in an area of 1 mm2. The proposed device accelerates the everyday use of thermoelectric modules as it is able to derive a large voltage of 0.65V from an atmospheric temperature difference of ten degrees.

The ultra-thin nanocrystal thermoelectric module is an innovative device capable of generating a voltage of 0.17V from body heat, and can convert small traces of heat energy in the surroundings into electrical energy. The ability to generate electricity from body heat implies that wearable medical sensors and IoT-based sensors can be utilized as a semi-permanent source of power. 

Prof. Kim said, “The proposed nanocrystal thin films, which convert waste heat from the human body and computers into electricity, can be applied to various wearable devices.”

[ Figure Description ]

▲ Figure 1. Generated voltages as a function of the temperature gradient and voltages of pn pairs

▲ Figure 2. Optical image and thermal image of the electricity-generating device. Voltage pulses generated by the touching of the pad with the finger.

Terminology:
1. Flexible thermoelectric module: A thermoelectric module, comprised of n-type and p-type elements, which can be bent or folded. The two materials are connected in series electrically, and then in parallel thermally. When there is a difference in temperature, the electrons flow from the hot to cold side and voltage is generated.

2. pn pair: Semiconductor materials are used as thermoelectric materials, and semiconductors are classified into n-type and p-type depending on carriers. A pn pair refers to an n-type and p-type material connected in parallel when creating a thermoelectric module.