Recent projects used inkjet printers to print multi-layer graphene circuits and electrodes but there were problems with the technology. Once printed, the graphene had to be treated to improve electrical conductivity and device performance which meant using high temperatures or chemicals. Both could degrade flexible or disposable printing surfaces such as plastic films or paper.
To avoid this, the team developed computer-controlled laser technology that selectively irradiates inkjet-printed graphene oxide. The treatment removes ink binders and reduces graphene oxide to graphene. The process increases electrical conductivity more than a thousand fold without damaging fragile printing surfaces.
"The breakthrough of this project is transforming the inkjet-printed graphene into a conductive material capable of being used in applications," explained assistant professor Jonathan Claussen.
"The laser works with a rapid pulse of high-energy photons that do not destroy the graphene or the substrate," Suprem Das, postdoctoral researcher, said. "They heat locally. They bombard locally. They process locally."
When that localised, laser processing changes the shape and structure of the printed graphene from a flat surface to one with raised, 3D nanostructures. The rough and ridged structure increases the electrochemical reactivity of the graphene, making it useful for chemical and biological sensors.
"This work paves the way for not only paper-based electronics with graphene circuits," the researchers claimed. "It enables the creation of low-cost and disposable graphene-based electrochemical electrodes for applications, including sensors, biosensors, fuel cells and medical devices."