Self-healing material shows conductivity boost under strain

An international team of researchers has developed a new self-healing material for wearable devices that exhibits increased conductivity when stretched. 

conductivity
(Credit: KIST)

Described in ACS Nano, the material is the work of a collaboration between Stanford University and the Korea Institute of Science and Technology (KIST). It is based on a previous polymer developed by the team that is highly elastic, can self-heal without the help of external stimuli, and has a mechanical strength similar to that of human skin, making it comfortable to wear for long periods of time. The new material has additional silver nanoparticles embedded within it, enabling it to function as an ‘interconnect’ or conduit that can transmit biosignals from the human body to an electronic device.

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During tests, the material was attached to the body to measure biometric signals in real-time. The signals were then transmitted to a robotic arm, which successfully imitated the movements of a human arm in real-time. Furthermore, when stretched, the polymer’s electric conductivity increased, which is unlike similar materials. Under a tensile strain of 3,500 per cent, conductivity rose over 60-fold, according to the researchers.

“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 utilised in the development and commercialisation of next-generation wearable electronic devices,” said KIST researcher Hyunseon Seo.

The team also investigated the new phenomenon of ‘electrical boosting’, which refers to the self-improvement of electrical conductivity through the rearrangement and self-alignment of the nanoparticles when the material is stretched. Using SEM and microcomputed tomography, the researchers were able to pinpoint the mechanism that was facilitating the boost. According to KIST, this feature – in combination with the self-healing and stretchability – should open up a range of applications for the material.

“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,” said KIST senior researcher, Dr Donghee Son.

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