Nanotechnology Now - Press Release: Tokai scientists create the world's first electronic skin-based sensor for heatstroke detection

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Historically heatstroke is a serious illness that can potentially damage many victims every year. When the body temperature rises over 40 deg Celsius for a long time lead to severe neurological disorders, even death. Open-air workers, older people, infants and athletes are at the highest risk of heatstroke. The usage of commercial on the body temperature sensor, electrocardiogram, electromyography confined to the laboratory. A simple device capable of detecting heatstroke by individuals is still lacking. A simple skin sweat pH monitoring would provide extensive information about your body but performing measurement directly on the skin is challenging to reveal the real-time body conditions.

We have seen a rapid growth wearable sensor platform for personalized healthcare and fitness monitoring. The sensors team head Prof.Kazuyoshi Tsuchiya, Department of Precision Engineering and Dr.Ganesh Kumar Mani, JSPS Post-Doctoral fellow, Micro/Nano Technology Center had come up with an idea inspired by temporary tattoo to create the on-body electronic skin based pH sensors.

The complete electronic skin sensor consists of an electrolyte free reference electrode (Ag/AgIO3) and Sb/Sb2O3 based thin film working electrodes. The researchers used the simple spin coating method to produce the freestanding nanosheet, and the sensing electrodes were deposited by sputtering.

The nanosheet material was chosen as polydimethylsiloxane (PDMS) due to its thermal stability and excellent biocompatibility. The key material for this electronic skin-based pH sensor is Ag/AgIO3 discovered by Prof. Tsuchiya, who is the team head for microneedle and nanosheet based sensors at Micro/Nano Technology Center.

The most exciting part about this process is to dissolve the sacrificing layer, which is made up of cellulose acetate and release the nanosheet with sensing electrode without any damage. Finally, the sensor was tested with perspired human sweat for real-time investigation and proved that the measurement value is much similar to the commercial pH meter. The researchers also performed the temperature-dependent performance on the human body and declared difference in potential difference due to temperature was minimum. Furthermore, mechanical testing of the nanosheet was tested with twisting and bending of the nanosheet which is placed on an artificial arm, found there visible crack or damage was observed.

The scientists state someday these electronic skin sensor patches could be seen in most of the people like the mobile phones present now. Dr.Ganesh says this nanosheet sensor technology would be the next frontier in personalized point of care technology. When different kind of nanosheet stacked, a variety of new sensors can be produced for a wide range of applications, Prof.Tsuchiya said.

In the next step, they plan to examine the adhesiveness with skin for its long-time usage, more improved sensitivity and to integrate with multiple analyte sensors. This progress will help them better understand the strategies of using such sensors in the real-world environment.

The preparation of ultrathin polymer thin films was developed initially by Prof.Youske Okamura, Department of Applied Chemistry, School of Engineering and it can be applied to the internal organs without the use of glue. Aiming for this freestanding nanosheet technology to be used worldwide, Tune Co., Ltd was founded in 2018 by young researchers from Micro/Nano Technology Center, Tokai University. Prof.Rio Kita, Director of Micro/Nano Technology Center, Department of Physics, lead the entire team with a perfect vision.

The research was supported by the Japan Society for the Promotion of Science (P19076, 19H04021).