Linh T. Le

Temperature-dependent electrical properties of graphene inkjet-printed on flexible materials.

Graphene electrode was fabricated by inkjet printing, as a new means of directly writing and micropatterning the electrode onto flexible polymeric materials. Graphene oxide sheets were dispersed in water and subsequently reduced using an infrared heat lamp at a temperature of ~200 °C in 10 min. Spacing between adjacent ink droplets and the number of printing layers were used to tailor the electrodes electrical sheet resistance as low as 0.3 MΩ/□ and optical transparency as high as 86%. The graphene electrode was found to be stable under mechanical flexing and behave as a negative temperature coefficient (NTC) material, exhibiting rapid electrical resistance decrease with temperature increase. Temperature sensitivity of the graphene electrode was similar to that of conventional NTC materials, but with faster response time by an order of magnitude. This finding suggests the potential use of the inkjet-printed graphene electrode as a writable, very thin, mechanically flexible, and transparent temperature sensor.

Inkjet-printed graphene for flexible micro-supercapacitors

Here we report our multi-institutional effort in exploring inkjet printing, as a scalable manufacturing pathway of fabricating graphene electrodes for flexible micro-supercapacitors. This effort is founded on our recent discovery that graphene oxide nanosheets can be easily inkjet-printed and thermally reduced to produce and pattern graphene electrodes on flexible substrates with a lateral spatial resolution of ∼50 µm. The highest specific energy and specific power were measured to be 6.74 Wh/kg and 2.19 kW/kg, respectively. The electrochemical performance of the graphene electrodes compared favorably to that of other graphene-based electrodes fabricated by traditional powder consolidation methods. This paper also outlines our current activities aimed at increasing the capacitance of the printed graphene electrodes and integrating and packaging with other supercapacitor materials.