Engineers at Duke University have devised a new technique for printing electronics that could be used for e-tattoos or tailored healthcare.
The researchers claim it is the first ever ‘print-in-place’ method for creating flexible electronics, where no processing is required at any stage of fabrication. It’s also gentle enough so that wearable electronics could be printed directly on to the skin, opening up possibilities for biosensors, smart bandages and electronic tattoos.
“When people hear the term ‘printed electronics,’ the expectation is that a person loads a substrate and the designs for an electronic circuit into a printer and, some reasonable time later, removes a fully functional electronic circuit,” said Aaron Franklin, Associate Professor of Electrical and Computer Engineering at Duke.
“Over the years there have been a slew of research papers promising these kinds of ‘fully printed electronics,’ but the reality is that the process actually involves taking the sample out multiple times to bake it, wash it or spin-coat materials onto it. Ours is the first where the reality matches the public perception.”
The Duke technique sees a printer first laying down a semiconducting strip of carbon nanotubes. Once that dries, two silver nanowire leads that extend several centimetres from either side are printed. A non-conducting dielectric layer of a two-dimensional material, hexagonal boron nitride, is then printed on top of the original semiconductor strip, followed by a final silver nanowire gate electrode. This all happens in situ without any processing other than drying between the stages. The work is published in ACS Nano.
“Nobody thought the aerosolised ink, especially for boron nitride, would deliver the properties needed to make functional electronics without being baked for at least an hour and a half,” said Franklin.
“But not only did we get it to work, we showed that baking it for two hours after printing doesn’t improve its performance. It was as good as it could get just using our fully print-in-place process.”
Despite the success of the technique, the Duke team believes it is more likely to be used for prototyping and personalised applications rather than large scale manufacturing of wearables.
“Think about creating bespoke bandages that contain electronics like biosensors, where a nurse could just walk over to a work station and punch in what features were needed for a specific patient,” said Franklin. “This is the type of print-on-demand capability that could help drive that.”