A one-step approach to green and scalable production of graphene inks for printed flexible film heaters

In recent years, the fabrication of printable graphene inks has attracted considerable attention. However, obtaining green and scalable production of these types of inks with high electrical conductivity using simple methods has always been challenging. Herein, a novel one-step method for preparing graphene inks by microfluidization was developed. Moreover, the resistances of graphene film heaters based on the condensed graphene inks using the screen printing method were adjustable. The results show that the obtained inks contained 1 to 5 layers of graphene with high quality. The prepared graphene films exhibit high electrical conductivity (9.7 × 104 S m−1) and their heaters have fast heat-generating performance; typically, after 5 printing passes, the heater reaches a high temperature of 111 °C within 100 s under 3.0 V, and further rising to a higher temperature of 193.4 °C under 5.0 V. Favorable flexibility and durability are also maintained; specifically, no apparent change of resistance of the graphene film heater can be detected after 5000 times of bending and flexing. The prepared flexible graphene film can be used for heating elements and wearable devices.