Wet Transfer of Inkjet Printed Graphene Micro-Supercapacitors
Authors: Sollami Delekta Szymon , Li Jiantong , Östling Mikael 
Published: February 2020

In terms of mechanical and electronic characteristics, graphene is a fascinating discovery and certainly deserves the nickname of “wonder” material. As a matter of fact, this 2-dimensional carbon allotrope holds a number of record qualities1,2 which grant benefits in a plethora of applications. Biomedical devices,3 transistors,4 energy storage and conversion5 and solar cells6 are all proved uses of graphene and, consequently, the research community has high expectations for the real-world future of this disruptive technology. Moreover, where surface area, high throughput and easiness of fabrication are preferred like in energy storage devices, sensors and solar cells, graphene can be produced through the liquid-phase exfoliation of graphite which yields graphene flakes.7 As for graphene flakes deposition methods, inkjet printing has the main advantage in the fact that the patterning is direct and happens during the deposition. The technology also boasts micro-scale resolution and good substrate versatility as compared to other printing techniques.8 However, the choice of substrate is still not entirely straightforward as wetting and other surface properties of the substrate affect the printed film significantly and post-treatment of the inks is required.
Herein, we demonstrate a wet transfer technique of inkjet printed graphene enabling the production of graphene patterns with a fine resolution on a range of substrates. Inspired by wet transfer methods of mostly CVD-grown graphene which have been subject of research since 2007, this process aims to expand their uses and capabilities through their implementation with inkjet printed graphene. The versatility of the technique allows depositing devices on a number of substrates, including plastics, silicon dioxide, plastics, paper (Figure 1a) and 3D objects. From the SEM images (Figure 1b) the protruding graphene flakes are visible, which are typical of inkjet printed graphene and greatly increase the surface area of the film. It can also be seen that the thin films maintain their structural integrity during the process. The cyclic voltammetry curves show that the energy storage mechanism is purely based on electrical double layer capacitance (Figure 1c), with an areal capacitance of about 120 µF/cm2.
Because of its versatility, low cost and substrate compatibility, we expect this technique to boost the use of graphene for a number of applications such as epidermal electronics, human monitoring and environmental sensors.

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Figure 1. a)Optical image of micro-supercapacitor on common paper. b)SEM image of the graphene film. c)Cyclic voltammetry performance of micro-supercapacitors on paper at scan rates from 5 to 250 mV/s.

Figure 1