Why Graphene-Based Printed Flexible Circuit and Conductive Inks for Electronic applications are the Way Forward

The world of electronics is changing. There has always been a drive to build solid, rigid components, so that they are less likely to become damaged or broken in electronic devices. This focus is starting to be flipped on its head since scientists have discovered that nanomaterials can be formulated into an ink and printed to provide electronically conductive pathways. This has already been realised commercially in some television display prototypes, but the potential is much wider than just displays.

There is a big drive these days to create flexible and wearable electronics, such as flexible phones, monitoring devices in areas where there are occupational exposure hazards, health and fitness monitoring devices, radio frequency (RF) identity tags, various other sensors, and energy storage devices. These are just a few examples. Many of these applications are not going to be possible with existing circuit board and electronic technologies, as the components are too rigid to conform to the desired surface or user. This is why printed electronics are the next key thing for the electronic world and are being brought about by advances in conductive inks and flexible circuits that can be printed.

Nanomaterials have seen use in these areas due to their small size, which also helps to create thinner and smaller technologies, which is another focus area for many technology companies nowadays. This means that thinner layers of ink can be printed, which ultimately leads to the realisation of smaller, yet efficient, technologies.

Why Graphene?

Yes, it is true that there are many nanomaterials out there that are electrically conductive, but there are many more factors and properties that need to be considered if a material is to be used in printed electronic applications. However, if we first consider electronic conductivity, in its pure form, graphene has some of the best electrical conductivity and charge carrier mobility properties of any material. Whilst it’s true that these properties do alter once it has become functionalised and formulated into an ink, these properties are still better than many other nanomaterials out there.

But it’s perhaps the other properties of graphene that makes it a well-suited material for conductive inks and printed electronics. Graphene is a very stable material, and is stable to harsh chemicals, high temperatures, pressures and stress/strain. Given the issues that have arisen in some of today’s electronics, and that these printed and flexible electronic devices are going to be used directly by consumers, the long-term stability of the material used is of utmost importance. A high thermal stability is very important as many electronic devices can emit a lot of residual heat, and a high resistance to heat/high temperature is a very important factor for a material’s long-term use in an electronic device.

The next important property that graphene possess is its ability to be flexed, and when coupled with its high tensile strength, can be used in many foldable and conformable electronic technologies without breaking. Of all the nanomaterials, the tensile strength of graphene is known to be one of the highest, which alongside the organic composition and thin nature of the sheets, enable it to be flexed more than other nanomaterials which are often more rigid. Not all nanomaterials are rigid, but it’s the ability to exhibit many of the required properties that is important.

The final property which is useful for display-based applications, is graphene’s optical transparency. A single layer has an optical transparency of 97.7%, and whilst this does decrease with an increasing number of layers, once the graphene has been evenly dispersed within an ink, it can become

optically transparent. So, even if the display itself does not use graphene, it means that some of the other components in the device could be transparent as well.

Overall, there are many nanomaterials out there that could provide one or two of these properties. However, because graphene exhibits them all, it is seen as the way forward for a rapidly changing electronics industry, where the focus is now more about making printable, flexible and wearable electronics. The cost of graphene is also coming down year on year, so the cheaper it becomes, the greater the added benefits to cost ratio will become, and we may soon start to see its widespread use in the not too distant future.