While the field of printable electronics holds a great deal of promise, the printing of circuits onto curved surfaces is still very challenging. A new technique greatly simplifies the process of doing so, potentially allowing for new types of electronic devices.
The procedure was developed at North Carolina State University, by a team led by Yuxuan Liu, Yong Zhu, Brendan O’Connor, Michael Zheng and Jingyan Dong. It addresses two shortcomings of existing techniques for printing circuits onto existing surfaces.
First of all, the conductive inks used in such circuits typically have polymer binding agents added to them, to help them initially stick to the substrate material. Those agents impair conductivity, however, so an extra step is required to remove them once the circuit has been printed.
Additionally, such circuits can usually only be printed directly onto flat surfaces. That's where the new technique comes in.
It begins with the creation of a template, which incorporates a pattern of microchannels – these make up the pattern of the desired circuit. That template is used to create a thin elastomer membrane, in which the same microchannel pattern is reproduced. The flexible membrane is subsequently applied to the curved target surface, channel-side-down.
A liquid solution containing silver nanowires and ethanol – but no binding agent – is then drawn into the membrane by capillary action, filling the cavities formed by the microchannels. After the solution dries, the membrane is removed, leaving behind a functional silver-nanowire circuit that conforms to the contours of the surface.
In proof-of-concept tests performed so far, the scientists have created a contact lens that could be used to measure fluid pressure in the eye; a latex glove with integrated pressure sensors that could give robots or prosthetics a sense of touch; and a flexible transparent electrode that might find use in solar cells or touch-sensitive panels.
"We think this could be scaled up pretty easily, in terms of manufacturing," said Zhu. "We’re open to talking with industries who are interested in exploring this technique’s potential."
A paper on the research was recently published in the journal Science Advances.
Source: North Carolina State University