Graphene offers significant promise for fiber applications of the future

Graphene is a wonder that I believe represents the next phase of nanoevolution. It is, in fact, my new favorite material.

Graphene is one single atomic layer of carbon. Graphite is many layers of graphene stacked. Separating the layers in graphite by various processes (termed exfoliation) is the way most commercially available graphene is made. This is called nanoplate graphene and results in some monolayer graphene along with what is commonly referred to as “few-layer graphene.” The International Organization for Standardization (ISO) defines graphene as a single layer of carbon atoms with each atom bound to three neighbors in a honeycomb structure, and few-layer graphene as 3-10 layers.¹

The history of graphene dates back to the 1800s, but it only started to gain momentum from an application perspective in 2004 when Professor Sir Andre Geim and Professor Sir Kostya Novoselov of the University of Manchester isolated a single atomic layer and were awarded the Nobel Prize for their efforts. This marked the first time, on record, that graphene was extracted from graphite.

In making this breakthrough, the two professors utilized a rudimentary approach, executed with a piece of sticky tape. Essentially, they took a simple piece of tape and repeatedly stuck it to a flake of carbon graphite and pulled off smaller flakes until they managed to create flakes that were just one atom thick … graphene. And with this, the possibilities opened up.²

What’s so cool about graphene?

Graphene is interesting because it is 200 times stronger than steel; it conducts electricity and heat more efficiently than copper; it is flexible, transparent and extremely stable (if properly produced); and can withstand temperatures in excess of 4,000 C.³ This means its potential applications are virtually limitless.

Aside from its purely mechanical attributes, graphene fibers reflect all types of light and are capable of absorbing Far Infrared Radiation (FIR) to help maintain temperature. Meanwhile, graphene-based textile fibers can provide cut resistance, thermally stability and a trifecta of anti … anti-bacterial, anti-static, and anti-ultraviolet.

Graphene applications

Graphene is a versatile molecule, which, as noted above, possesses many unique and desirable properties.

Transportation applications are a natural fit for graphene due to its light weight and extreme strength, with aircraft and spacecraft affording near-term cost effectiveness. Batteries, where graphene’s light weight and strength are also advantageous, can benefit from graphene’s conductive characteristics to enable the reduction of charging times up to an order of magnitude or higher.

Researchers at Brown University recently showed that multilayer graphene can provide a two-fold defense against mosquito bites. The ultra-thin yet strong material acts as a barrier that mosquitoes are unable to bite through. At the same time, experiments showed that graphene also blocks the chemical signals mosquitoes use to sense that a blood meal is near, blunting their urge to bite in the first place. The findings suggest that clothing with a graphene lining may be an effective mosquito barrier.

Researchers at the University of Manchester have been engineering graphene flakes to develop graphene-based yarns that can be knitted into a garment for use as a flexible sensor to send temperature or pressure data to a device via Bluetooth or radio frequency identification (RFID).

Nazmul Karim, Ph.D., Knowledge Exchange Fellow (Graphene), at the National Graphene Institute, University of Manchester, explained how his research team used graphene oxide to coat textile yarn. “Pure graphene, derived from mechanical exfoliation, is not scalable, so we used a liquid phase exfoliation to produce reduced graphene oxide [rGO],” he says. Using a very simple dyeing machine, the team produced electro-conductive textile yarns that can be knitted into garments.

The coated yarn has “excellent temperature sensitivity” reported the team, responding to even small changes in temperature. The yarn was exposed to mechanical agitation (using 10 steel balls) and washing powder to simulate a typical laundry cycle, and it remained conductive after 10 washes.

“We are focusing on using existing machinery, processes and systems,” said Dr. Karim. “Scalable production will reduce the cost for high-performance, functional clothing, which can be anti-bacterial, anti-static and fire retardant.”

Another possible application for graphene is in plastics recycling. Today, recycling plastics degrades the quality of the material. On average, plastics can only be recycled three times; but adding graphene to recycled plastics can improve its strength so that it can be recycled many more times.

Other applications where graphene is attracting interest range from biomedical (cancer treatment) to defense (explosive detection) to infrastructure (longevity of roads) sports (racing bike tires) to instrumentation (air sensors) to heat management (heating films) to telecommunications (cellphone technology) to water treatment (purification) and the list goes on.¹

Graphene is interesting because it is 200 times stronger than steel; it conducts electricity and heat more efficiently than copper; it is flexible, transparent and extremely stable (if properly produced); and can withstand temperatures in excess of 4,000 C.³

Challenges for graphene

The main challenge for graphene is up-scaling production. Current processes for graphene fiber include conventional melting and wet spinning for large-scale production. Beyond the scaling of technology, the largest secondary challenge lies in maintaining quality in large quantities of graphene. Defects on the graphene monolayer carbon network are particularly troublesome, as any missteps will dramatically affect all of graphene’s attributes, as its two-dimensional structure makes the material particularly sensitive to defects.

Since graphene is so new from a material application perspective, it will also have to be tested and validated. There is no historical data, so it all has to be developed. Likewise, because nanotechnology is a rapidly emerging field, more information will likely become available about potential health and safety hazards associated with some nanomaterials. The health hazard potential depends on the particular nanomaterial and the exposure level. Few occupational exposure limits exist, specifically for nanomaterials. Certain nanoparticles may be more hazardous than larger particles of the same substance. Therefore, existing occupational exposure limits for a substance may not provide adequate protection from nanoparticles of the same substance.

What the future will bring

Graphene will bring enormous benefits to the fiber industry. Initially most likely as an additive to composites, and as the technology evolves it figures to enable the development of such revolutionary technologies as super strong and flexible yarns that can be woven into materials and outlast current materials on a variety of fronts. For example, filter media constructed of graphene would most likely outlast the supporting equipment in the systems, creating a new sales model based on equipment up-time verses replacement filters. Another example could be a landfill media with graphene fiber that would provide a barrier material for waste containment.

Researchers all over the world continue to investigate graphene to learn its various properties and possible applications. The graphene patent estate is growing as the appetite for commercialization grows more voracious. Cost and, possibly, regulations figure to be the only obstacles for technology development. Nanotech can change the properties of fibers, which is a fact that must be considered from a health and safety perspective. It may be better to work with caution so that bans will not set back development The first commercial nanomaterial in an aerosol nearly killed 80 people the first day on the market.⁵

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