A new study from Nottingham University has discovered how to use inkjet-printed graphene to 3D-print novel electronic devices with useful properties, such as an ability to convert light into electricity.
The £5.85m, EPSRC-funded project was carried out by engineers at the Centre for Additive Manufacturing and physicists at the School of Physics and Astronomy.
Researchers found that it is possible to jet inks, containing tiny flakes of 2D materials such as graphene, to build up and mesh together the different layers of these complex customised structures. They also used quantum mechanical modelling to pinpoint how electrons move through the 2D material layers, to understand how the devices can be modified in the future.
Co-author Professor Mark Fromhold, head of the School of Physics and Astronomy, said: “According to the laws of quantum mechanics, in which the electrons act as waves rather than particles, we found electrons in 2D materials travel along complex trajectories between multiple flakes. It appears as if the electrons hop from one flake to another.”
Two-dimensional materials like graphene are usually made by sequentially exfoliating a single layer of carbon atoms, arranged in a flat sheet, which is then used to produce bespoke structures. However, producing layers and combining them to make complex sandwich-like materials has been difficult, usually requiring deposition of the layers one at a time and by hand.
There has been an exponential growth in the number of patents involving graphene since its discovery, however in order to exploit its potential, scalable manufacturing techniques must be developed.
Published in Advanced Functional Materials, the new study titled ‘Inter-Flake Quantum Transport of Electrons and Holes in Inkjet-Printed Graphene Devices’ shows that additive manufacturing (3D printing) using inks in which tiny flakes of graphene are suspended provides a promising result.
Co-author Dr Lyudmila Turyanska, from the Centre for Additive Manufacturing, commented: “Our results could lead to diverse applications for inkjet-printed graphene-polymer composites and a range of other 2D materials. The findings could be employed to make a new generation of functional optoelectronic devices; for example, large and efficient solar cells; wearable, flexible electronics that are powered by sunlight or the motion of the wearer; perhaps even printed computers.”
Researchers used a range of characterisation techniques – including micro-Raman spectroscopy, thermal gravity analysis, a novel 3D orbiSIMS instrument and electrical measurements – to provide detailed structural and functional understanding of inkjet-printed graphene polymers, and the effects of annealing on performance.
Their next steps will be to better control the deposition of the flakes by using polymers to influence the way they align and trying different inks with a range of flake sizes. The researchers also hope to develop more sophisticated computer simulations of the materials and the way they work together, developing ways of mass-manufacturing the devices they prototype.