Reactive inkjet printing of graphene based flexible circuits and radio frequency antennas

Graphene-based materials show great promise in wearable electronics due to their remarkable properties such as excellent electrical conductivity, high flexibility and light weight. Various techniques have been used to fabricate graphene-based electronics, such as lithography, template-assisted synthesis, and chemical vapor deposition. However, these patterning methods normally involve complex procedures, toxic solvents and extra machinery, which are highly challenging for large-scale industrial production. Herein, we have developed an in situ approach to fabricate reduced graphene oxide (rGO) conductive patterns on flexible substrates via reactive inkjet printing without any post-treatment. Electronic circuits and WIFI antennas consisting of conductive rGO lines with a minimum width of 100 μm and remarkable mechanical durability were successfully fabricated. The highest electrical conductivity of the printed rGO lines was 2.69 × 104 S m−1 using optimised printing conditions. The rGO based radio frequency antenna demonstrated transmission with a measured domain name system (DNS) delay of 243 ms. When accessed via a 100 Mbps router, the network speed reached up to 4.64 Mbps, which is comparable to that of the current commercial mobile phone antenna (DNS delay 237 ms, network speed 4.73 Mbps). This demonstrates the potential of reactive inkjet printing for the industrialisation of graphene-based wearable electronics.