Graphene is an emerging market, and as always, production methods are refined and improved as its applications grow—which in turn allows for more applications. The discovery of a production method for low cost, high quality, large surface area graphene flakes and coatings will be the true trigger for the graphene market to explode into the medical (and consumer) markets, and will have a deep and lasting impact on people’s health worldwide.
 
I’ve known for a while that graphene is pretty darn cool, but in an effort to learn even more, I decided to take an 8-week course through Coursera by Dr. Aravind Vijayaraghavan that taught me a lot more. If you don’t have time to take the course, I’ve distilled a few key takeaways here.
 
Let’s start with the basics: graphene is a single layer of carbon atoms in a very particular hexagonal structure. Graphite, most famous for its use in pencils, is actually hundreds and thousands of layers of graphene piled on top of each other, like a big stack of paper. This structure is why a pencil sometimes sheds little flakes—not a lot of other materials do that. Like all objects in the universe, graphene is three-dimensional, but often referred to as a 2D material because it is so thin (only 0.3nm thick).
 
For a long time, 2D materials (that is, super thin free standing materials) were thought impossible. The thinking was they would fall apart, curl up, or otherwise disintegrate because they have no rigidity in the third dimension. It turns out that 2D graphene naturally folds up into small ridges (almost like corrugated cardboard) and can maintain its structure this way. (These findings, and the discovery of graphene, were awarded a Nobel Prize in 2004). Without going into the detail other articles have covered, graphene is not only the first "2D" material, but is also far superior to conventional materials in conductivity, in-plane strength, and a whole bunch of other neat properties poised to revolutionize medical technology.
 
So, how do we make graphene in an affordable way? That might be the single most lucrative question in the world at the moment, but let’s look at what is being done today:
 
Mechanical Separation
This is the method via which graphene was discovered. In a shining example of how amazing things don’t need to be complicated, this manufacturing method is so simple it can be done at home. First, a sample of graphite is stuck to a surface. Layers are removed from the opposite side, one at a time, using an adhesive such as Scotch tape, until only one layer remains.
 
This method results in the best quality of graphene with the highest strength and charge mobility. Unfortunately, this method does not yield single pieces larger than a couple millimeters, and is quite expensive.
 
Average size of homogenous flake: Large (>1mm)
Price (comparative): High
 
Molecular Ribbons
Here, the individual atoms are essentially assembled one by one in a row. The quality is very high, and the shape can be defined by growing the ribbons into any shape desired. Unfortunately, the ribbons do not have any substantial length, resulting in very small flakes. Similar ribbons can also be made by “unzipping” premade nanotubes into flat ribbons, similar to cutting along a tube to get a flat sheet.
 
Average size of homogenous flake: Small (~ 1um)
Price (comparative): High
 
Chemical Vapor Deposition (CVD)
Though a large surface area can be covered, the quality is not quite as good as the mechanical separation or molecular methods. In this method, carbon atoms are essentially “sprayed” on a substrate of any size and shape. Because of this, CVD has applications in biomedical devices. Another positive aspect of the CVD method is that it is already used in many other industries for depositing thin, even layers coatings onto various substrates.
 
Average size of homogenous flakes: Large (up to 1mm)
Price (comparative): Median
 
Silicon Carbide Sublimation
In this process, good quality graphene is grown on top of a silicon wafer via a sublimation process. The main area of application for this type of manufacturing is electronics, where silicon wafers are already used to make components.
 
Average size of homogenous flake: Median (up to 50um)
Price (comparative): Median
 
Liquid Phase Exfoliation
Produced as a liquid with suspended graphene flakes, it could theoretically be “painted” onto any surface to produce a coating containing graphene flakes, or used in conjunction with another process to ensure an even layer. The charge mobility, as expected of this low cost mass production method, is very poor, almost 10,000x worse than a pure flake produced by mechanical separation.
 
Average size of homogenous flake: Median (1-100um)
Price (comparative): Low
 
How Does This Apply to Biomedical Engineering?
The biomedical market is a great starting point for high performance, high cost technologies like graphene, and this has not escaped the world’s experts. Practically, chemical vapor deposition and liquid phase exfoliation methods hold the most promise, as they can be essentially sprayed or painted onto any surface. This way, they could be made in a biocompatible way in a variety of scenarios. Ribbons also have applications in sensors, but may not be practically long enough. One day, production methods entirely different from those listed here might allow the creation of cheaper, larger pure flakes that can open the door to all types of biomedical applications.

Nigel Syrotuck is a mechanical engineer at Starfish Medical. His background includes a diverse project development portfolio including sustainable power solutions, assisted living devices, and nano-satellite design.