No batteries are required, and you can say so long to Bluetooth or other digital chips. Normally, these components are needed to send bio-signals from a wearable sensor to a smartphone or a tablet. These rigid devices add to the physical bulk and can make the whole system more susceptible to damage. Not so with a new wearable sensor developed by researchers at the Massachusetts Institute of Technology (MIT). Meet e-skin. While it may sound like something from our dystopian future, the electronic skin that the team has developed is more akin to Scotch tape: a flexible semiconducting film that adheres to the skin of the wearer.
How does this e-skin work? It relies on the two-way piezoelectric properties of the compound gallium nitride, which does the double duties of mechanically vibrating with the introduction of an electrical impulse, and responding to mechanical strain by producing an electrical signal. Researchers were able to use the dual-action nature of gallium nitride to sense bio-signals and wirelessly communicate data at the same time.
The touch of gold: in testing their e-skin, MIT researchers paired gallium nitride with a layer of gold to boost the conduction of incoming and outgoing electric signals. The result was a film that vibrated in response to the wearer’s heartbeat and reacted to the salt in sweat, generating an electric signal that was wirelessly transmitted to a nearby readable device. Though researchers believe that e-skin can detect a broader range of bio-signals. MIT researcher Jun Min Suh says, “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.”
All of these features require only minimal power. Researcher Jeehwan Kim explains, “Chips require a lot of power, but our device could make a system very light without having any chips that are power hungry.” And minimal in size: the sample e-skin the MIT researchers worked with has a thickness of 250 nanometers, which is around 100 times thinner than an average human hair. Kim says, “You could put it on your body like a bandage, and paired with a wireless reader on your cell phone, you could wirelessly monitor your pulse, sweat, and other biological signals.”