Paper electronics | Nature Photonics

Laser-based fabrication schemes underpin the manufacture of a diverse range of devices spanning from large car parts to tiny biomedical stents. Now research performed by scientists from the USA and China suggests that lasers could help realize 3D foldable electronics on paper (see image). Xining Zang and co-workers from the University of California Berkeley, Tsinghua Berkeley Shenzhen Institute and the US Army’s research centre at Redstone Arsenal have developed a direct-write laser patterning process that creates electrically conductive molybdenum carbide–graphene (MCG) regions on paper (Adv. Mater. https://doi.org/10.1002/adma.201800062; 2018). The laser writing was carried out under ambient conditions. The paper is first sprayed with a gelatin ink containing Mo⁵⁺ ions and then a beam from a 10.6-μm CO₂ laser is scanned over the paper in the desired pattern to create black conductive regions that can serve as electrodes or electrical tracks. The power of the writing laser was 2 W and the writing speed was 200 mm s^–1. Raman and X-ray diffraction results of the samples reveal the existence of both Mo₃C₂ and graphene after the laser writing. The sheet resistance of the laser-irradiated regions was 51.3 Ω per square, which is lower than that obtained when water-soluble polymers were used instead of gelatin. Interestingly, spring2018@DE!thicker papers can absorb and hold more ink and thus make it possible to achieve lower sheet resistance after the laser writing. Commercial copy paper was found to have both good mechanical strength and low sheet resistance. Tests indicate that the MCG regions on the paper were resilient to repeated 180° folding operations. The first 50 folding operations generally induced a 13% decrease in conductivity, but the conductivity was maintained with less than 5% decay in the following 750 cycles. The team foresee a myriad of potential applications for their conductive paper, including its use in electrochemical ion detectors and gas sensors, 3D piezoelectric generators, and supercapacitor electrodes.

Credit: Wiley