University researchers in Tokyo have developed a hypoallergenic electronic sensor, allowing long term health monitoring which can be worn on the back of a hand. Its thin and stretchable shape makes it the perfect fit for letting the skin breathe naturally and it is so light that some wearers forget they even have it on, according to the researchers.
The hypoallergenic electronic sensors can monitor heart rate and other vital health signals over a long period of time. During testing it showed they can be worn for a week without discomfort or irritation. The elastic electrodes, constructed of breathable nanoscale meshes, hold promise for the development of non-invasive e-skin devices that can monitor a person’s health continuously.
Wearable electronics that monitor heart rate and other vital health signals have made headway in recent years, with next-generation gadgets employing lightweight, highly elastic materials attached directly onto the skin for more sensitive, precise measurements.
However, there are side effects to the ultrathin films and rubber sheets used in these devices. Despite their comfortable wear, the lack of breathability prevents sweating and blocks airflow around the skin causing irritation and inflammation. Ultimately this could lead to lasting physiological and psychological effects.
Professor Takao Someya at the University of Tokyo’s Graduate School of Engineering said: “We learned that devices that can be worn for a week or longer for continuous monitoring were needed for practical use in medical and sports applications”. Someya’s research group had previously developed an on-skin patch that measured oxygen in blood.
In the current research, the group developed an electrode constructed from nanoscale meshes containing a water-soluble polymer, polyvinyl alcohol (PVA), and a gold layer—materials considered safe and biologically compatible with the body. The device can be applied by spraying a tiny amount of water, which dissolves the PVA nanofibers and allows it to stick easily to the skin—it conformed seamlessly to curvilinear surfaces of human skin, such as sweat pores and the ridges of an index finger’s fingerprint pattern.
The researchers next conducted a skin patch test—for irritations and skin allergies—on 20 subjects and detected no inflammation on the participants’ skin after they had worn the device for a week. The group also evaluated the permeability, with water vapour, of the nanomesh conductor—along with those of other substrates like ultrathin plastic foil and a thin rubber sheet—and found that its porous mesh structure exhibited superior gas permeability compared to that of the other materials.
Furthermore, the scientists proved the device’s mechanical durability through repeated bending and stretching, exceeding 10,000 times, of a conductor attached on the forefinger; they also established its reliability as an electrode for electromyogram recordings when its readings of the electrical activity of muscles were comparable to those obtained through conventional gel electrodes.
“It will become possible to monitor patients’ vital signs without causing any stress or discomfort,” says Someya about the future implications of the team’s research. In addition to nursing care and medical applications, the new device promises to enable continuous, precise monitoring of athletes’ physiological signals and bodily motion without impeding their training or performance.