The Massachusetts Institute of Technology (MIT) has developed an electronic skin or e-skin that can be easily peeled off from the skin like a bandage. The e-skin is made of a semiconducting film that perfectly sits on the skin and is used to measure the heart rate, glucose and cortisol levels in the blood, and the amount of salt in sweat. Its communication with the skin happens wirelessly as it is not equipped with chips, wires, or batteries.
Most of the wearable tech, as we know, is equipped with batteries, wires, sensors, and chips. Take, for example, the smart clothes developed by Purdue University that monitor the body’s vitals. Their smart clothes are washable and communicate with the skin wirelessly through WiFi or radio waves. This happens because the conducting coil and nano-circuitry are embedded into the textile fabric.
However, the case of MIT’s e-skin is a little different. The device, to start with, is not made out of e-textile. And it also does not have any conducting coils embedded in its structure. The way that it communicates with the skin is through the materials used in its making.
Materials used to fabricate e-skin
The electronic skin is made from gallium nitride, a stretchable material that supports piezoelectric properties. The piezoelectric property of a material is defined as the conversion of mechanical input or mechanical strain such as stretching into electrical energy or signals. The researchers found that stretching the gallium nitride material generates electrical signals.
In their study published in Science, Yeongin Kim et al. found that gallium nitride, when coupled with gold, generated electrical signals with vibrations made by each heartbeat and sweat produced. The gold layer used here boosted the input and output signals.
Engineers fabricate a chip-free, wireless electronic “skin”: The device senses and wirelessly transmits signals related to pulse, sweat, and ultraviolet exposure, without bulky chips or batteries. https://t.co/eOqFoPP6pP pic.twitter.com/he1vII0ga4
— Massachusetts Institute of Technology (MIT) (@MIT) August 19, 2022
Layers on e-skin
The piezoelectric gallium nitride membrane used in the study was 100 times thinner than a human’s hair. This means the membranes are susceptible to the surface acoustics of the skin, such as the heart’s lub-dub. When the gallium nitride is coupled with a thin and ion-sensing membrane, it can measure the amount of salt in sweat.
The authors also suggested that changing the layers on gallium nitride changes what it measures. Co-author Jun Min Suh explained that “if you change the sensing membrane, you could detect any target biomarker, such as glucose, or cortisol related to stress levels”.
The study’s results also suggest that the surface acoustic wave-based e-skin can be used in the long term and is highly sensitive to mechanical strain, UV light, and ions in sweat. This method is inexpensive and can be connected to health monitoring devices.