Researchers developed a novel technique to print wearable sensors on the skin without using heat!
Researchers from Pennsylvania State University, Harbin Institute of Technology in China, and several other Chinese institutions have developed printed, electronic, wearable sensors. ‘Printed’ here does not refer to the usual printing; in fact, here it is in terms of printing on the skin!
Not only they successfully found a way to print sensors onto the skin, but also devised a way that does not use heat for printing. Typically, the bonding of silver nano particles requires high-temperature sintering. However, this process is not suitable for skin printing for obvious reasons. Therefore, the researchers developed a sintering layer made up of polyvinyl alcohol and calcium carbonate. These two do not require high temperatures to bind. In fact, the nanoparticles can now bind at room temperature.
Ling Zhang, a researcher in the Harbin Institute of Technology in China and in Cheng’s laboratory, said:
“In this article, we report a simple yet universally applicable fabrication technique with the use of a novel sintering aid layer to enable direct printing for on-body sensors.”
Huanyu Larry Cheng, Dorothy Quiggle Career Development Professor in the Penn State Department of Engineering Science and Mechanics, said:
“The skin surface cannot withstand such a high temperature, obviously. To get around this limitation, we proposed a sintering aid layer. Something that would not hurt the skin and could help the material sinter together at a lower temperature. By adding a nanoparticle to the mix, the silver particles sinter at a lower temperature of about 212 F (100 C). That can be used to print sensors on clothing and paper, which is useful; but it’s still higher than we can stand at skin temperature. We changed the formula of the aid layer, changed the printing material and found that we could sinter at room temperature.”
Not only it allows a heat-free process, but the printed electronic sensor is smooth and flexible for the skin. This allows for a comfortably wearable and high-quality recording.
The printed sensors can record and detect blood oxygen, ECG, temperature, and humidity. Moreover, the researchers linked these sensors for real-time transmission of readings to a nearby monitor.
These electronic sensors, after printing on the skin can stay on for a few days while measuring various body parameters. The process of removal is easy too. A hot shower makes them even easier to peel off. Above all, the sensors are not destroyed during the removal and can be reused and recycled.
“It could be recycled since removal doesn’t damage the device. And, importantly, removal doesn’t damage the skin, either. That’s especially important for people with sensitive skin, like the elderly and babies. The device can be useful without being an extra burden on the person using it or to the environment.”