New Technique Introduces Curved Circuits for Varying Applications

North Carolina State University engineers have showcased a novel technique that allows circuits to be printed on curved surfaces. Their technology opens doors for soft electronic technologies. So far, the team has used this approach for developing smart contact lenses, transparent electrodes, and pressure-sensitive latex gloves.

"There are many existing techniques for creating printed electronics using various materials, but limitations exist," says Yong Zhu, corresponding author of the paper. "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."

First, the researchers produced a template for specific applications integrating a "pattern of microscale grooves." This template copies that pattern in a thin elastic polymer film, which attaches to the matching flat or curved substrate. Then, these grooves are filled with a solution holding silver nanowires. After the solution dries at room temperature, it changes into a soft material taking on specific circuit patterns and shapes.

The team then developed three prototypes. The first, a smart contact lens containing circuits, measures the eye's fluid pressure and can be used in the biomedical field. Their second one is a flexible, transparent electrode containing grid-patterned circuity, suitable for solar cells or touch displays. Lastly, the latex glove has printed circuits functioning like pressure sensors, perfect for robots and human-machine interfaces.

"We think this could be scaled up pretty easily in terms of manufacturing," Zhu adds. "We’re open to talking with industries who are interested in exploring this technique’s potential.”