Bench Talk

(Source: Shawn Hempel - stock.adobe.com)

Electronic devices are advancing in many ways. Two of the main drivers is to make electronic devices smaller and to make them flexible (for the wearable electronics market). Conventional circuits can only be made so small and are not generally flexible enough to accommodate the conformal changes needed for flexible/wearable electronic applications. There are two options which have emerged as an alternative to conventional circuits. The first is nanowires (or molecular wires) which have been discussed in a previous article, and conductive nanomaterial inks, which will be the focus of this article.

In terms of the commercial potential, the usage of nanomaterial-based inks is a lot further along than nanowires are, although there are instances where silver nanowires have been formulated into inks for use in commercial prototypes. Nanomaterial-based inks do have their formulation and optimization issues—just like any formulation does—but the commercial potential far outweighs that of other options, and this is why much research is being put in by companies to overcome the issues, scale up the production, and make them a viable option for many commercial applications.

Nanomaterial-based inks come in many forms and use everything from 2D sheets of nanomaterials, to 3D nanoparticles and 1D nanowires, while encompassing a wide range of potential elemental compositions. Once the nanomaterials have been incorporated into an ink form (ink formulation), then they can be applied to a surface to act as a conductive medium between different electronic components, and the inks essentially becomes a printable, flexible and ultra-thin electronic circuit.

Graphene has shown some of the most promise due to its inherent flexibility, electrical conductivity and charge carrier mobility properties, but there are others which are also being trialed for commercial applications—with copper nanoparticles and silver nanowires being a couple of potential options. But as it stands, the field is wide open, and so long as it can get past some of the initial teething problems that any new formulation has, then there’s a huge potential to revolutionize the flexible/wearable electronics markets, as well as make many everyday devices smaller.

Some of the biggest challenges standing in the way of their widespread use is finding the best approaches to uniformly produce the nanomaterials, efficiently disperse the nanomaterial into inks, and to uniformly print them on the surface. One key factor is that all these areas are interlinked and are involved with the optimization of the inks, including their optimization for larger production volumes (i.e., scale up), so the task at hand is not as scary as it may initially sound.

On the nanomaterial side, several raw products can be produced with size and property differences which can affect the final ink formulation. For formulations, if the active nanomaterials are not dispersed uniformly, it can lead to regions of high conductivity and no conductivity meaning that the ink cannot be used as a complete circuit. Moreover, the printing on to a surface needs to be uniform as to avoid a surface which has regions of varying thickness. All three of these areas are some of the key challenges facing the conductive nanomaterial inks sector, and these are the areas that are currently being worked on.

As with any new product—and especially nanomaterials—there are always going to be concerns regarding safety. However, that is something for another day as it is an entire area within itself, but a lot of process is being made on the nanosafety front to make them suitable for consumer use and less hazardous to workers.

Given that the applications are in electronics, all these challenges need to be optimized and perfected before we see widespread use of nanomaterial inks in everyday products. However, looking at just the challenges is not the best way forward, as there are many companies, government bodies and association looking to tackle these challenges and it’s best to look at the potential once these areas have been ironed out.

Moreover, nanomaterial conductive inks are still an early-stage technology, and like many technologies, devices and products, need to go through efficient product development, optimization, and scale up stages before they are fit for widespread commercial use. So, it’ll only be a matter of time before they are used across many sectors, as the science behind them is sound—as showcased by the large amount of academic work that has been done— and it is merely the processing and development stages that need to be perfected.

One thing to note, is that the production of nanomaterial inks is going to have to be scaled up and produced in much larger volumes than is the case currently, otherwise they will not be financially competitive in an already competitive market. Again, the projects and research involved with increasing nanomaterial ink production are also looking to reduce the cost of the products as well as making them more uniform—and of a better quality—so it is likely that both the cost and quality factors will make progress simultaneously.

The application potential is vast, and prototypes have already been made in the flexible device and solar cell space to create new capacitive touch screens and ultra-thin copper indium gallium selenide (CIGS) photovoltaics (PVs), respectively. Developments out of universities have also seen the realization of prototype textile products that use conductive nanomaterial inks circuits to links sensors and data transmission points together for health and fitness monitoring applications.

While these are a few areas that are already showing commercial potential and are already in the prototype stage, there are also many others that have potential to utilize conductive nanomaterial inks. Other applications include LCD displays, LED devices, thin-film transistors, radio frequency identification (RFID) tags, medical sensors, and transparent electrodes, to name a few. Moreover, any application which is looking to use flexible or wearable technology is a key application area for nanomaterial inks. The area of printable devices is another future consideration, as some components can already be printed, and the combination of printable components with printable nano-ink circuits could also help to propel the printable device sector forward.

There is a huge amount of potential for nanomaterial-based inks to make flexible, wearable, and printable electronic devices a widespread commercial reality, as well as help to reduce the size of many everyday devices. This can be done by the inks acting as a conductive conduit between components so that it essentially becomes a printed, flexible and ultra-thin circuit.

Like any new type of formulation product, there have been some issues with optimizing the formulations and ensuring that they are applied uniformly. But this is no different to many other new technologies, and there are many people out there—from industry to funding bodies—who are working hard to overcome these challenges. If they prevail, then nanomaterial inks have a huge amount of potential for many electronic devices, from CIGS PVs to flexible touchscreens, and many more applications in between.