Scientists develop ‘electronic skin’ that transmits info without a chip or battery

By Danny Halpin via SWNS

A new electronic 'skin' powered by the heart beat can transmit biological information without the need for a chip or battery.

The electronic skin — or e-skin — is a flexible film 100 times thinner than the width of human hair that conducts electricity and can be applied to the body like a bandage.

Within that is a sensor made of gallium nitride, which can pick up biological signals as well as receive information wirelessly from a smartphone.

Corresponding author Professor Jeehwan Kim, of Massachusetts Institute of Technology (MIT) in the US, said: “Chips require a lot of power, but our device could make a system very light without having any chips that are power-hungry.

“You could put it on your body like a bandage, and paired with a wireless reader on your cellphone, you could wirelessly monitor your pulse, sweat, and other biological signals.”

The engineers wanted to build on the current generation of wearable sensors that have chips and batteries embedded inside, the technology they say is too bulky for the smaller, thinner, more flexible forms being developed.

In the study, published in the journal Science, the team paired gallium nitride with a layer of gold to boost incoming or outgoing electrical signals.

The device was sensitive enough to vibrate in response to someone’s heartbeat as well as the salt in their sweat and these vibrations produced an electrical signal that could be picked up by a nearby receiver.

This biological activity creates acoustic waves which ripple across the film and form patterns that can then be transmitted.

Assistant Professor Yeongin Kim of the University of Cincinnati and the first author of the study said: “If there is any change in the pulse, or chemicals in sweat, or even ultraviolet exposure to skin, all of this activity can change the pattern of surface acoustic waves on the gallium nitride film.

“And the sensitivity of our film is so high that it can detect these changes.”

When testing their idea, the engineers used a pure film of high-quality gallium nitride paired with a layer of gold to boost the electrical signals that are transmitted.

The film, which they consider to be a sample of electronic skin, measures just 250 nanometres thick – about 100 times thinner than the width of a human hair.

They placed the e-skin on volunteers’ wrists and necks and used a simple antenna to pick up the device’s frequency without physically touching the sensor itself.

The device was able to sense and wirelessly transmit changes in the surface acoustic waves of the gallium nitride on volunteers’ skin related to their heart rate.

When paired with an ion-sensing membrane – a material that selectively attracts a target ion, in this case sodium – the device could sense and wirelessly transmit changing sodium levels as a volunteer held a heat pad and began to sweat.

The researchers said their results are the first step towards chip-free wireless sensors and they envision that they current device could be paired with other selective membranes to monitor other biological signals.

Co-author of the study and MIT postdoctoral associate Jun Min Suh added: “We showed sodium sensing, but if you change the sensing membrane, you could detect any target biomarker, such as glucose, or cortisol related to stress levels. It’s quite a versatile platform.”