Flexible electronics have opened up some interesting possibilities when it comes to wearable sensors that can be applied to the skin, taking the form of tattoo-like films and sleeves that monitor various aspects of human health. Scientists at Penn State University have now developed one they say can be safely printed directly onto the skin, where it can track things like body temperature and blood oxygen levels, before being washed off once the job is done.
The new printable sensors build on earlier work by the same researchers, in which they developed flexible circuit boards for use in wearable sensors. But a key part of this process involved bonding some of the metallic components together at the kinds of temperatures not well tolerated by the human body, at around 572 °F (300 °C).
This scorching hot sintering process is what had prevented the team from printing their flexible circuit boards directly onto 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.