Ally Winning, European Editor, PSD
The vast majority of electronics circuits use printed circuit boards to lay out the design. PCBs tend to be relatively bulky and rigid, which rules out many useful applications. There are many use cases that could be imagined if we had a more flexible ways of creating circuits. Printing the circuit onto surfaces offers the easiest way to do this, and a lot of research has been done on printed electronics. However, all of the techniques used so far tend to have limitations. Most of these existing techniques use polymer binding agents in the ink that is printed on to the surface, but the binding agent has a detrimental effect on the circuit’s conductivity, so it has to be removed after printing. This requires additional manufacturing steps. Furthermore, the majority of circuit printing techniques require a flat surface, which would rule out a number of important applications. However, a newly discovered technique may be able to overcome these problems.
Researchers from North Carolina State University have published a paper describing a way to print electronics circuits, even on curved or corrugated materials. Initially a template is created for the application that incorporates a specific pattern of microscale grooves. The pattern from the template is then recreated on a thin elastic polymer film. That film is then attached to the relevant substrate. Next, the polymer film’s tiny grooves are filled with a liquid solution containing silver nanowires. The solution then left to dry at room temperature, leaving the silver nanowires behind in a soft material that is moulded to the desired shape and circuit pattern.
“The new technique doesn’t require binding agents and that allows us to print on a variety of curvilinear surfaces. It also allows us to print the circuits as grid structures with uniform thickness.” says Yuxuan Liu, first author of the paper and a Ph.D. student at NC State.
The researchers created three proof-of-concept prototypes; a “smart” contact lens to measure the fluid pressure of the eye, a flexible, transparent electrode with circuits printed in a grid pattern for applications such as solar cells or touch panels and a latex glove with pressure sensing circuits for robotics and human-machine interface applications.
Yong Zhu, corresponding author of a paper on the work, and the Andrew A. Adams Distinguished Professor of Mechanical and Aerospace Engineering at NC State continued, “we think this could be scaled up pretty easily, in terms of manufacturing and we are open to talking with industries who are interested in exploring this technique’s potential.”
The paper describing the technique 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. The work was done with support from the National Science Foundation.