The new technique is known as MIMIC and allows engineers to print circuits on everything from latex gloves to contact lenses. (Image credit: NC State)
Engineers at NC State have developed a novel technique to print flexible circuits on curved and corrugated surfaces. Known as MIMIC (MIcroMolding In Capillary), the technique was used to prototype smart contact lenses, pressure-sensitive latex gloves, and transparent electrodes. The engineers hope their work paves the way for a myriad of new soft technologies.
“There are many existing techniques for creating printed electronics using various materials, but limitations exist,” says Yong Zhu, principal investigator at the Department of Mechanical and Aerospace Engineering. “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.”
The new technique doesn’t require bonding agents to print onto curved surfaces but instead relies upon creating a template for the relevant application that incorporates a specific pattern of microscale grooves. That template is then used to replicate that pattern in a thin, flexible polymer film. A thin polymer film is then attached to the patterned substrate, which can be flat or curved. The tiny grooves embedded in the polymer are then filled with a liquid solution containing silver nanowires, which is then dried at room temperature, leaving behind silver nanowires in a soft material with the desired shape and circuit pattern.
As mentioned earlier, the engineers created three proof-of-concept prototypes, including smart contact lenses that measure fluid pressure for bio-applications. Another featured a flexible, transparent electrode that could be used in solar cells or touch panels, while the other was designed around a latex glove with printed circuits that served as pressure sensors for human/machine applications.