SAINT faculty Seongpil An and Il Jeon co-research team, developed a highly transparent and multifunctional wearable nanogenerator

-Multifunctional piezoelectric nanogenerator for energy harvesting and motion sensing in next-generation wearable electronics

-Winner of 2022 SKKU Graduate Student Paper Award

▲ (From left) Professor Seongpil An, Doctoral student Kiyong Kim, Doctoral student Sangsu Lee, Professor Il Jeon.

Profs. Seongpil An and Il Jeon’s co-research team from SKKU Advanced Institute of Nanotechnology (SAINT) announced that they have developed a multifunctional transparent composite that can harvest energy, composed of piezoelectric polymer nanofibers and high-purity carbon nanotubes (CNTs) as the core materials.

In previous studies, silver nanowires or electrically conductive polymers, such as PEDOT:PSS, were used as electrodes for transparent PENGs. However, metal-based transparent PENGs have inherent issues of opacity due to their natural light reflection and scattering, while electrically conductive polymer-based PENGs have shown material limitations in mechanical properties with insufficient electrical conductivity.

The co-research team developed a multifunctional transparent composite capable of harvesting energy using a silicon-based elastomer embedded with piezoelectric polymer nanofibers and high-purity CNTs. The team developed piezoelectric P(VDF-TrFE) nanofibers with a diameter of 500 nm, 200 times thinner than a human hair, using the electrospinning technique and embedded them in a transparent silicon-bsed elastomer PDMS. They also used a differentiated aerosol-assisted chemical vapor deposition (CVD) method to produce transparent CNT films for their use as electrodes in the development of a transparent PENG.

The electrospinning and aerosol CVD methods used in this study are not only simple to use but also easily scalable to larger production scales compared to other methods. Based on these excellent process advantages, it is expected to have a positive impact on the commercialization of related technologies in the future. In particular, in this study, the conductivity of the CNT electrode could be improved by 3.1 times through a simple chemical doping method.

The developed high-transparency PENG demonstrated decent energy harvesting performance that generated a voltage of 10 V or more even with relatively weak external force (F = 10 N). Additionally, it showed high energy harvesting performance under repetitive external force conditions of over 50,000 cycles, proving excellent mechanical durability and stability. Furthermore, when the external force was applied through a body part, such as fingers, it exhibited higher energy harvesting performance of up to 26.8 V through an additional effect of triboelectricity.

▲ Transparent PENG developed and its fabrication process

It is expected that the newly developed transparent PENG can be applied extensively in the rapidly growing fields of metaverse, virtual/augmented reality, as it can not only detect subtle movements of the human body in real time by attaching it to various parts of the body, but also generate voltage signals sensitively in response to changing external forces.

This study was published on January 18th in Advanced Functional Materials (IF: 19.924), a world-renowned academic journal in the top 5% of the material science field, based on the results that won the SKKU Graduate Student Paper Award. The lead authors of this paper are beginner in doctoral course, so their future research activities are highly anticipated.

※ Title: Highly Transparent and Mechanically Robust Energy-harvestable Piezocomposite with Embedded 1D P(VDF-TrFE) Nanofibers and Single-walled Carbon Nanotubes

※ Journal: Advanced Functional Materials

※ DOI: https://onlinelibrary.wiley.com/doi/10.1002/adfm.202213374