In a significant development, Massachusetts Institute of Technology (MIT) engineers have developed a new category of wireless wearable skin-like sensors for health monitoring.
According to MIT, the new sensor called ‘e-skin’ is an ultrathin semiconductor film made of a piezoelectric substance that adheres to the skin, sensing the vibrations of the body. Additionally, the sensor does not require any power source.
According to Yeongin Kim, the first author of the study, and a former MIT postdoc scholar, “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.” Kim is now an assistant professor at the University of Cincinnati.
Wearable sensors are useful for tracking our health since they are wireless and continuously monitor things like one’s blood pressure, heart rate, glucose levels, and others. This development by MIT engineers is a distinct type of wearable sensor that is able to send signals related to pulse, sweat, and ultraviolet exposure, without using bulky chips or batteries.
Furthermore, activity levels are then smoothly sent from the sensor to the smartphone for further analysis and interpretation of the findings. This innovation paves the way for chip-free wireless sensors.
Moreover, the heart of the sensor is an ultrathin film of gallium nitride, a material that can both produce an electrical signal in response to mechanical strain and mechanically vibrate in response to an electrical impulse.
The piezoelectric material can generate an electric signal when mechanical strain is applied and will vibrate when electricity is passed through it. It can therefore sense as well as transmit signals wirelessly. Researchers have used a high-quality film of gallium nitride as piezoelectric material.
Currently, most wireless sensors communicate via embedded Bluetooth chips powered by small batteries. However, as health-tracking wearables increase in popularity, scientists have been searching for a way to design next-generation sensors, which are taking on smaller, thinner, more flexible forms.
The researchers hypothesised that a gallium nitride-based sensor, adhered to the skin, would have its own inherent, ‘resonant’ vibration or frequency that the piezoelectric material would convert into an electrical signal.
Besides, any change to the skin’s conditions, such as an accelerated heart rate, would affect the sensor’s mechanical vibrations, and the electrical signal that it automatically transmits.
“Chips require a lot of power, but our device could make a system very light without having any chips that are power-hungry,” said Kim.
He further said that “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”. “The sensitivity of our film is so high that it can detect these changes,” Kim added.