Transfer printing and hydrogels key to new wearable electronics

Increasing demand for electronic devices that conform to the skin is posing difficulties for the medical sector. Both wearables and sensor-based electronics that can be printed onto adhesive patches are proving valuable for gathering data about the human body, whether for wearers to monitor their own health or for clinicians to keep tracks on patients at home or in hospitals. But most of the methods for constructing electronic devices and the connections necessary for them to work are suited to printing onto flat and rigid surfaces, rather than clothing-like substrates or plasters.

At the Korea Institute of Science and Technology's (KIST) Post-Silicon Semiconductor Institute, Hyunjung Yi and her colleagues have developed a method for producing high-performance sensors on flexible substrates of diverse shapes and structures by using a combination of hydrogels and nano ink in a transfer-printing process.

Transfer-printing is a popular method for assembling electronic devices, as the devices are assembled onto a transfer mould surface and then printed onto their final substrate. It avoids the problems inherent in assembling onto the difficult shaped and flexible surfaces needed for wearables. The KIST method takes advantage of the highly-flexible nature of hydrogels to form the shapes of the sensors required, while the connections and sensors themselves are formed from the conductive aqueous solution-based nano ink.