Scientists at Penn State University have developed a wearable sensor that can be safely printed directly onto the skin to track things like temperature and blood oxygen levels. The printable sensor looks a bit like a high-tech henna tattoo and can be used to continuously record human data. Once the job is done, you can simply wash the printable sensor off.
Flexible electronics have led to many possibilities when it comes to wearable sensors, but this is the first time scientists have been able to safely print such a device directly onto the skin. A key part of this process involves bonding some of the metallic components together at around 572 °F (300 °C), temperatures that are unbearable for the human body. This scorching hot sintering process is what had prevented the team from printing their flexible circuit boards directly onto the human skin, but it may have now found a way around this problem.
The key is what the scientists call a sintering aid layer, which acts as a kind of buffer and enables the materials to bond together at far safer temperatures. The layer is made of polyvinyl alcohol paste combined with calcium carbonate, materials found in peelable face masks, and eggshells, respectively. This layer serves to smooth out the surface of the skin and allow a very thin layer of metal patterns to be printed directly on top at room temperature, which is then set with an air-blowing device.
Another cool aspect of the device is that it can be used over and over again. “It could be recycled since removal doesn’t damage the device,” says Huanyu Cheng, who led the research. “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.”
In the near future, the hope is to tailor the technology to monitor symptoms of COVID-19.
