Researchers from North Carolina State University (NCSU), have Demonstrated a new technique For printing electronic circuits directly onto curved or corrugated surfaces. The work paves the way for a variety of new soft electronic technologies, and researchers have used the technique to create prototype “smart” contact lenses, pressure-sensitive latex gloves, and transparent electrodes.
“There are many existing techniques for creating printed electronics using various materials, but limitations exist,” says Yong Zhu, corresponding author of a paper on the work. “One challenge is that existing techniques require the use of polymer binding agents in the ‘ink’ you use to print the circuits. This impairs the circuit’s conductivity, so you have to incorporate an additional step to remove those binding agents after printing.
“A second challenge is that these printing techniques typically require you to print on flat surfaces, but many applications require surfaces that aren’t flat,” says Zhu, who is the Andrew A. Adams Distinguished Professor of Mechanical and Aerospace Engineering at NC State.
“We’ve developed a technique that doesn’t require binding agents and that allows us to print on a variety of curvilinear surfaces,” says Yuxuan Liu, first author of the paper and a PhD student at NC State. “It also allows us to print the circuits as grid structures with uniform thickness.”
The first step of the new technique is to create an application template that incorporates a particular pattern of microscale grooves. This template is used to create a thin elastic film that replicates the pattern. Researchers attach the thin layer of polymer to the appropriate substrate. This can be flat or curvy. The liquid solution containing silver nanowires is then poured into the small grooves of the polymer. Allow the solution to dry at room temperature. This will leave behind silver nanowires in soft materials with the desired shape.
Three proof-of-concept prototypes were created by the researchers to demonstrate the technology. One was a “smart” contact lens with built-in circuits, which could be used to measure the fluid pressure of the eye—which is relevant for some biomedical applications. One was a transparent, flexible electrode that had circuits printed in grid patterns. This could be used on touch panels or in solar cells. A third glove made of latex has pressure sensors printed on it. It is used in robotics and human-machine interaction applications.
“We think this could be scaled up pretty easily, in terms of manufacturing,” Zhu says. “We’re open to talking with industries who are interested in exploring this technique’s potential.”
The paper, “Curvilinear Soft Electronics by Micromolding of Metal Nanowires in Capillaries,” is published in the open-access journal Science Advances. The paper was co-authored by Brendan O’Connor, a professor of mechanical and aerospace engineering at NC State; Jingyan Dong, a professor in NC State’s Edward P. Fitts Department of Industrial and Systems Engineering; and Michael Zheng, an undergraduate at NC State.
This press release was first published on the North Carolina State University’s website.