Gold Used to Create Sensor for Measuring 2 Biosignals Simultaneously

Scientists already have created a range of biosensors that can measure biological signals in the human body in a non-invasive way. Now researchers in South Korea have developed a new sensor that can measure two biosignals simultaneously, paving the way for easier fabrication of novel wearable technology that can do the same, they said.

A team led by Professor Sei Kwang Hahn and Dr. Tae Yeon Kim from the Department of Materials Science and Engineering at Pohang University of Science and Technology (POSTECH) used various shapes of gold nanowires to achieve their design goals for the newly developed sensor, which can measure both temperature and strain.

“This research underscores the potential for the development of a futuristic bioelectronics platform capable of analyzing a diverse range of bio-signals," Kwang Hahn said of the work.

While various scientists already have made strides in developing wearables capable of measuring multiple biosignals concurrently, there have been challenges along the way that have slowed advancements. 

One is the disparate materials needed for each signal measurement, which has led to interface damage, complex fabrication, and reduced device stability. Meanwhile, the analysis of the different signals also requires further signal processing systems and algorithms, according to scientists.

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The Gold Standard

Typically it's nanowires made of silver and known for their extreme thinness, lightness, and conductivity that are commonly used in wearable devices. To create the nanowires for the new sensor, the researchers  fused them with gold, initially by developing bulk gold nanowires by coating the exterior of the silver nanowires. 

Following the creation of bulk gold-infused nanowires, the team then proceeded to create gold nanowires, which they did by selectively etching the silver from the gold-coated nanowires. They found that the bulk gold nanowires responded sensitively to temperature variations, whereas the hollow gold nanowires showed high sensitivity to small changes in strain.

The next step in the process was to pattern the nanowires onto a substrate made of styrene-ethylene-butylene-styrene (SEBS) polymer, seamlessly integrating them without separations. The result of the process was an integrated sensor that could simultaneously measure both temperature and strain.

Next-Generation Wearable System

By combining the sensor with a custom logic circuit for signal analysis, the team developed an intelligent wearable device system that not only captures but also analyzes signals at the same time, the researchers said.

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In tests, the sensor demonstrated an ability to detect subtle muscle tremors and could identify heartbeat patterns, recognize speech through vocal cord tremors, and monitor changes in body temperature, the team reported. Moreover, the sensors showed stability without damaging the material interfaces and their flexibility conformed to human skin in a user-friendly way.

The news may be of interest to those working on healthcare applications as well as those working on integrated electronic systems.