New Wearable Sensor Can Be Printed Directly on the Skin

Flexible electronics have led to exciting possibilities for the development of wearable sensors.

In June 2019, researchers at the University of Texas, Austin, showed off an electronic tattoo technology for monitoring heart health. A few months after that, we saw a wearable device that generates power from sweat.

Similarly, an international team of researchers developed flexible circuit boards for wearable sensors. An essential part of the process involves bonding some of the metallic components at around 572°F.

Since the temperature is too high for our body to tolerate, the team has never printed their flexible circuit boards onto human skin. But a recent report suggests that they’ve found a way around the problem.

The key is to use what the scientists are calling a sintering aid layer. Not only does the layer serve as a buffer, but it also enables the materials to bond at room temperature.

In a statement, the first author of the study and researcher at the Harbin Institute of Technology in China, Ling Zhang 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.”

The team described their work in the journal ACS Applied Materials and Interfaces.

Printing a Wearable Sensor on the Skin at Room Temperature

To create the sintering layer, the researchers combined a polyvinyl alcohol paste with calcium carbonate.

The mixture resulted in a material that could smooth out the skin’s surface. What’s more, it enabled the printing of thin layers of metal patterns directly on the skin at room temperature, which is set using an air-blowing device.

Since the flexible circuit retains its electrochemical properties, the researchers could tune it to record various data continually. These include heart signals, humidity, blood oxygen, and temperature.

After collecting data with the wearable sensor, the user can simply wash it out of their skin using hot water.

“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.”

The researchers are currently working to improve the device. With further development, they hope to tailor the technology to monitor COVID-19 symptoms.