Contact electrification is a well-known phenomenon in physics, in which opposite charges are created at surfaces due to continuous contact and separation processes occurring between two materials, followed by the generation of electric potentials between them. Triboelectric nanogenerators based on the phenomenon have not only been successfully demonstrated for use as power sources that are sufficient for powering small electronic devices, but they have also been used for sensing momentary stimuli in electronic skin, touch screens, healthcare devices, and habit-recognition security systems.

However, the physical contact between two surfaces may have some big drawbacks in TENGs, such as decreases in their output power due to the wear of materials, the need to replace the device, and noise resulting from its operation. Sungkyunkwan University (President Dong Ryeol Shin) has developed a non-contact mode triboelectric nanogenerator with a new dielectric, a C60-containing block polyimide (PI-b-C60). compared with perfluoroalkoxy alkane film-based TENGs, the TENG based on PI-b-C₆₀ generated 4.3 times higher output power and a superior charge density of over 300 μC m⁻² with a 3 times slower charge decay rate.

With the superior characteristics, a keyless electronic door lock system and a speed sensor with a tone wheel for a car with very sensitive and reliable operations, were developedfor the first time.

Team also for the first time suggested  a new paradigm to increasing the output voltage of a thermoelectric generator that does not involve material modification by introducing the contact electrification.

Thermoelectric energy harvesting is a technology that generates useful energy by utilizing the temperature difference generated at both ends of a material when heat is applied from the outside. But there was still a difficulty in commercialization due to the very low output voltage.

As a solution to these challenges, the research team created a polyimide-based polymer layer having negative charges as a triboelectric effect in the cold side of the BiSbTe-based thermoelectric device, which has the highest ZT value at room temperature. As a result, the output power has more than doubled and the world's highest output voltage (50% increase over the previous version) has been achieved.

Prof. Baik said “These accomplishments by introducing the contact electrification is the breakthrough technologies for sustainable energy generation in energy harvesting research area.”

These studies were published online in Energy & Environmental Science (IF 30.287) and ACS Energy Letters (IF: 19.003).