Biomedical sensors typically perform their best when they’re placed in close proximity to the body. While wearables, such as wrist-worn heart rate monitors, are common these days, they are very limited by where they can be placed on the body, have poor signal quality, and are often uncomfortable to wear for extended periods. Now, researchers from Pennsylvania State University, Harbin Institute of Technology in China, and a few other Chinese institutions have developed a way to print electronic sensors, as well as the accompanying electronics, directly onto the skin without using any heat in the process. This allows for easily wearable, high quality recording of a number of vitals and body signals. High temperature sintering is normally required to bond silver nanoparticles together into flexible electronic components. At 572 degrees Fahrenheit (300 Celsius), this cannot be safely performed directly on the skin. To overcome this, this research team set off looking for a sintering layer, which would lower the required temperature for sintering the silver nanoparticles. They developed a sintering layer, consisting of a commonly used polyvinyl alcohol paste and calcium carbonate, that lets the nanoparticles bond at room temperature. While this sintering layer lets the process happen at room temperature, it also makes the surface of the resulting material smoother and still flexible for on-body applications. Using the technique, the researchers have already created blood oxygen, ECG, temperature, and humidity sensors directly on the skin. They also linked these sensors into a network which can transmit readings in real-time to a nearby monitor. Once these kinds of electronics are printed onto the skin, they can stay on for a few days while measuring various body parameters. When it’s time to take them off, a hot shower makes them easy to peel off. The devices can actually be reused and recycled, as they’re not damaged in the removal process. Source
