New Material Developed for Wearable Devices has Excellent Electrical Conductivity

Researchers have reported a novel material that simultaneously retains its properties, like self-healability, high electrical conductivity, and high stretchability, even after being exposed to adverse mechanical strain.

Contrary to typical materials, the electrical conductivity of which decreases when the shape of the materials is changed by an applied tensile strain, the new material developed by the KIST research team shows a dramatic increase in conductivity under a tensile strain of 3,500%. (Image credit: Korea Institute of Science and Technology)

The material was developed through joint convergence research. The research team was headed by researcher Hyunseon Seo; senior researcher Dr Donghee Son of the Korea Institute of Science and Technology’s (KIST, president: Byung-gwon Lee) Biomedical Research Institute; Professor Zhenan Bao of Stanford University (chemical engineering); and postdoctoral candidate Dr Jiheong Kang.

At present, there is a growing interest in the development of wearable electronic devices. Before this study, Dr Jiheong Kang, Dr Donghee Son, and Professor Zhenan Bao created a highly elastic polymer material that can heal on its own without the help of any external stimuli, even when subjected to sweat or water. Its mechanical strength is similar to that of human skin, thus making it easy and comfortable to wear for extended periods of time.

The KIST-Stanford researchers, in their most recent study, created a novel material that can be utilized as an interconnect—a material that acts as a channel for transmitting biosignals from the human body to an electronic device in a precise and stable way.

This is because the material possesses the same kinds of properties as current wearable materials. It also has high levels of stretchability and electrical conductivity, which facilitate the stable and precise transmission of data and electricity from the human body to electronic devices.

The KIST-Stanford research team dispersed silver micro-/nano-particles across the self-healable and highly stretchable polymer material. This was done to obtain a unique design for a nanocomposite material that has high electrical conductivity and high stretchability.

At the time of the tests, the newly developed material was used as an interconnect and fixed to the human body to enable real-time measurement of biometric signals. These signals were subsequently transmitted to a robotic arm, which effectively and precisely mimicked (in real time) the human arm’s movements.

The electrical conductivity (and thus performance) of standard materials reduces when their shape is altered by an applied tensile strain. By contrast, the novel material created by the KIST researchers exhibits a remarkable increase in conductivity under a tensile strain of 3,500%.

As a matter of fact, electrical conductivity increased more than 60-fold, resulting in the world’s highest conductivity level reported to date. Even if the new material is fully cut through or damaged, it is still able to self-heal, a trait that is already attracting a great deal of interest from academia.

Phenomena that are yet to be studied in current conductive materials were explored by KIST researchers. In the new material developed by the KIST team, the phenomenon showed electrical “self-boosting,” which refers to the self-enhancement of electrical conductivity via the self-alignment and rearrangement of a material’s micro-/nano-particles when it is expanded.

By using microcomputed tomography (μ-CT) and SEM analyses, the researchers also identified the mechanism of the dynamic behavior of micro-/nano-particles.

Our material is able to function normally even after being subjected to extreme external forces that cause physical damages, and we believe that it will be actively utilized in the development and commercialization of next-generation wearable electronic devices.

Hyunseon Seo, Researcher, Korea Institute of Science and Technology

Son stated, “because the outcome of this study is essentially the foundational technology necessary for the development of materials that can be used in major areas of the Fourth Industrial Revolution, such as medical engineering, electrical engineering, and robotics, we expect that it will be applicable to diverse fields.”

The study was performed with support from the Ministry of Science and Technology (minister: Young-min Yoo) as a project of KIST and the National Research Foundation of Korea. The results the study, which was performed in association with Stanford University, were reported in the latest issue of ACS Nano.


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