Gold nanowires revolutionise wearable sensor technology

Led by Professor Sei Kwang Hahn and Dr. Tae Yeon Kim from the Department of Materials Science and Engineering, the research team has developed an integrated wearable sensor device that measures and processes two bio-signals simultaneously.

Wearable devices, varying from attachments to patches, are increasingly significant in monitoring health, particularly in detecting physical, chemical, and electrophysiological signals crucial for disease diagnosis and management. Recent research advancements have focused on creating wearables capable of measuring multiple bio-signals at once. However, challenges like interface damage, complex fabrication, and reduced stability due to the use of disparate materials for each signal measurement have been significant hurdles, along with the need for advanced signal processing systems and algorithms.

Addressing these challenges, the POSTECH team has used gold (Au) nanowires in various shapes. While silver (Ag) nanowires are typically used in wearable devices for their extreme thinness, lightness, and conductivity, the team enhanced their functionality by fusing them with gold. The process involved developing bulk gold nanowires by coating the exterior of the silver nanowires, thereby suppressing the galvanic phenomenon. They further created hollow gold nanowires by selectively etching the silver from the gold-coated nanowires. The bulk nanowires were sensitive to temperature variations, whereas the hollow nanowires showed high sensitivity to minute changes in strain.

These gold nanowires were then adeptly patterned onto a substrate of styrene-ethylene-butylene-styrene (SEBS) polymer, integrated seamlessly without separations. By leveraging two distinct types of gold nanowires, the team engineered a sensor capable of measuring both temperature and strain. Further innovation was added by designing a logic circuit for signal analysis, using a negative gauge factor that resulted from introducing micrometre-scale corrugations into the pattern. This led to the creation of an intelligent wearable system capable of capturing and analysing signals simultaneously, all using a single material – gold.

In practical applications, these sensors demonstrated exceptional performance, detecting subtle muscle tremors, identifying heartbeat patterns, recognising speech through vocal cord vibrations, and monitoring body temperature changes. Notably, these sensors maintained high stability and adaptability to curved skin surfaces due to their flexibility and stretchability.

Professor Sei Kwang Hahn commented on the research’s implications, saying: “This research underscores the potential for the development of a futuristic bioelectronics platform capable of analysing a diverse range of bio-signals.”

He further emphasised the promising prospects this technology holds across various industries, including healthcare and integrated electronic systems.

This research was supported by the Basic Research Programme and the Biomedical Technology Development Program of the National Research Foundation of Korea, alongside funding from POSCO Holdings. The development marks a significant leap forward in wearable technology, opening new frontiers in healthcare monitoring and integrated electronic systems.