RESEARCHERS PUSH AHEAD WITH INNOVATIONS TO INTEGRATE GRAPHENE IN TEXTILES

BY SARAH GIBBONS, in London, and KATHRYN WORTLEY, in TokyoSMART e-textiles are set to revolutionise the industry in the coming years as the wonder material of the 21st century is introduced into an array of innovative applications.

Researchers believe designers will expand the use of graphene in textiles for bio-medical, sportswear, fashion, furnishings, military and security equipment.

Isolated by scientists from graphite in 2004, a layer of pure carbon, graphene is the thinnest known compound. It is just one atom thick (a million times thinner than a human hair), the strongest compound ever discovered (between 100-300 times stronger than steel), the lightest material (with one square metre weighing only 0.77 milligrams) and very flexible.

It is also the best-known conductor of heat and electricity, has the largest surface to volume ratio, is the most stretchable crystal, has the highest levels of thermal conductivity and is impermeable to all gases. This makes it a much sought after material.

Combined with oxygen to convert it into graphene oxide, when linked with other molecules or atoms it produces different chemical properties, thus extending the boundaries of its use, such as coatings on Kevlar, plastics and other materials and also other uses in different sectors such as battery production and automotive parts.

Research is also being carried out into creating graphene inks to incorporate into fabrics, integrating sensors into materials, coating product surfaces to make them conductive, weaving ribbons into textiles to create cables to attach electronic devices and manufacturing yarns from the material itself.

Such is the potential for its use across sectors, the European Commission launched the Graphene Flagship in 2013 as its biggest ever research initiative, with a budget of EUR1 billion (USD1.14 billion) – half provided by the European Union (EU) executive. It brings together academic and industrial researchers to take graphene into everyday use within 10 years, generating economic growth and new jobs.

The wearable sector “has the potential to be one of the largest end users of nano and two dimensional materials such as graphene,” according to a 2016 report by Spain-based Cientifica Research entitled ‘Wearables, Smart Textiles and Nanotechnologies: Applications, Technologies and Markets’. “The market for wearables using smart textiles is forecast to grow at a CAGR [compound annual growth rate] of 132% between 2016 and 2022, representing a USD 70 billion market,” said the report.

Project chair Professor Andrea C Ferrari, from the University of Cambridge engineering department’s graphene centre, said: “Introducing electronic conductive parts for sensors within the textile means things such as heart rate and breath can be analysed with user displays.

“This means you can have information on a patient in hospital and read about their diseases or the need for medicines remotely.

“If you have a link to this information then it’s only the creativity of the designers that limits us. If you think about current apps, that technology wasn’t being used 10 years ago.

“This is a basic ingredient, the hardware to support the software.

“We can now put in sensors relating to temperature and light in textiles then people will come up with brilliant ideas how to use them.

“Enabled devices in textiles allows different people to put in different functionality, for example have a ski map on your jacket to follow in real time on the outside of your jacket.”

Many demonstration products are expected to be on show at the Mobile World Congress in Barcelona from February 27 to March 2, where 100,000 visitors, including from companies such as Facebook and Google, will view the latest gadgets.

But these are not yet mass market products. Prof Ferrari noted: “Developers need to scale up to reduce costs. An individual flake of graphene in a lab is light, tough, resilient – the huge challenge is to preserve those qualities in large numbers in textiles as it loses a lot on mass.”

He told Future Materials that it usually takes 20 to 40 years for a new material to reach the mass market – but will that happen with graphene?

Dr Felice Torrisi, a lecturer who also works at the Cambridge graphene centre, may help sped up this process, having devised a process to embed graphene elements directly onto cotton.

He said: “Most of the current wearable technologies rely on rigid electronic components mounted on flexible materials such as plastic films or textiles. These offer limited compatibility with the skin in many circumstances, are damaged when washed and uncomfortable to wear because they are not breathable.

“We have developed a technique to put electronic systems directly into clothes. We first modified cotton to improve the adhesion of graphene, and increase the washability and durance of the textile. Then we designed an environmentally-friendly process to embed highly flexible graphene elements directly into cotton. We found out that the controlled arrangement of few microns of graphene flakes could be used to design a motion sensor simply from the graphene-based cotton fabric.”

This innovation would allow electronic systems to be integrated directly within clothes through graphene cotton fibres, he said: “The area of healthcare, wellbeing and sportswear can see enormous advantages by incorporating cotton fibre-based sensors into clothes for patients monitoring, pain treatment and drug delivery.

“The area of fashion-tech could easily take up this technology and build on it for future textile designs and advanced functional fabrics with sensing, light emitting and electronic properties.”

Dr Helena Alves, principal researcher at Aveiro University, in Portugal, has worked on an international team to transfer graphene onto polypropylene fibre already used in textiles.

“Devices can be attached to parts of the body to monitor pulse and other signs,’ she said. “For blood pressure and other vital signs, however, the best part of the body to check is the thigh where it is not comfortable to wear a device. To make it comfortable, we can add extra effects to a textile and transform its surface to introduce nano-devices into the fabric to measure small signals from the body.

She said the material could indeed create innovative substances bringing advances in healthcare and sport.

“It could improve the lifestyle of older people able to stay living alone but monitored remotely,” she said.

“Graphene also transports heat easily and can transform clothes. You could have a very thin shirt with a thin layer of graphene to keep you warm or conversely, when people are running and give out a lot of heat, they could use graphene to enhance the heat transfer away from the body into the environment. This could also be used for developing energy applications such as transferring heat from the body into the textile of a pocket where you could charge your mobile phone.

“Many people are looking at the thermal properties to keep people warm and this is the most feasible area to bring to the mass market quickly. It can transform a normal textile into an exceptional material.”

She noted how US thermal clothing company Oros is about to launch a range of gloves using graphene-coated aerogels to trap body heat.

Dr Alves added: “Companies are trying to invent LEDS so clothes have a display of information or built-in lights instead of using reflectors in the dark.”

These should be available in the next three to four years as commercial products, she suggested. As for bio-medical uses, while graphene offers the capability of embedding electronic devices, this is a more complex field and medical applications are strictly legislated, “so will take longer than leisure activities to benefit”.

One potential use was that “graphene could be put into sensors in face masks in polluted areas like some Chinese cities to show wearers how they are being exposed to toxic cases and should move away to a more secure area,” she said.

Dr Ana Neves, a lecturer in engineering at the UK’s Exeter University, also extolled the possibilities: “We could call this field fibretronics. Virtually all types of electronic devices that we currently use in our daily lives could be reproduced in textiles from a smart biometric t-shirt used by a high-performance athlete or by a patient at the hospital, so it’s really something that all of us could use.”

In the US, experts believe upholstery textiles might be the first to benefit from the properties of graphene ‘quantum dots’, essentially layers of the material spread across a product.

Dr James M Tour, Professor of Chemistry, Professor of Materials Science and NanoEngineering, and Professor of Computer Science at Rice University, Houston, Texas, said: “They go for years without photo-bleaching and can be put in upholstery to protect colours in areas that difficult…to wash.

“The first main product to market will be colour binding from dots, especially if it can be incorporated in a detergent to stick to the fabric. I think we’ll see it within a couple of years.

“We’ll also see clothing which can sense moods and give feedback information. You can create clothing to change colour if you’re feeling melancholy or excited – clothing becomes at one with you. It’s possible through small voltage inputs.”

He added that graphene can be an extremely good disinfectant and could d be used in bandages and healthcare professionals’ clothing and in underwear to prevent bacteria build-up. “It’s going to be useful for the military when they can’t wash for a long time – also in socks to prevent fungal infections,” he noted.

Such tech is being certainly being popularised, with Anushka Naiknaware, a 13-year-old schoolgirl from Oregon, US, reaching the finals of a Google science competition last October (2016) with her idea of a bandage embedded with graphene-based sensors showing doctors when it needs changing due to moisture levels, temperature or pH, thus improving healing times and reducing infection.

They could be viewed remotely wirelessly by phone and internet and save billions of dollars in wound treatment internationally, she argued.

This kind of applications have a clear role in sports. US-based GraphWear Technologies hopes its graphene-based SweatSmart patch which monitors users’ levels of glucose and hydration will soon be integrated into textiles.

“The concept of wearable devices will fade as they become what we call “disappearables”, said founder Saurabh Radhakrishnan. “These sensors and their relevant metrics should show up for users with minimal footprint on their daily life. The best way to do that is to integrate it into clothing without being visible or uncomfortable: “SweatSmart data can become part of daily life via clothing integration, giving users a blood test on a real-time basis,” he said.

Meanwhile, Italian brand Colmar has launched the first sportswear collection containing Graphene Plus, made by fellow Italian company Directa Plus.

Giulio Cesareo, Directa Plus CEO and founder, said: “We believe this is the beginning of a revolution in the world of sportswear and the textile industry as a whole.” Their collaboration has produced ski jackets and suits, technical underwear and a polo shirt.

Finally, in the automotive industry, work is ongoing to embed graphene in various construction textiles to create lighter, safer more energy-efficient cars, including bringing heated seats to a broader range of vehicles using transparent conductive sheets within the fabric – an effective energy save as the whole car does not need heating up to keep the driver and passengers warm, according to notes from the EU’s Graphene Flagship.

Graphene production is also ramping up in Asia. Japanese’s graphene market is set to grow as firms move to mass produce the material. Following success in halving the cost of graphene production in 2016, Osaka Gas is supplying the material from a research centre on a trial basis to about 10 companies, but aims at full-scale production. By 2020, the Adeka Corporation also intends to begin commercial production of graphene, reducing the price per kilogramme to about Japanese Yen JPY10,000 (USD87.31).

Opportunities to develop technical textiles using graphene therefore look promising, which is good news for firms such as high tech manufacturer Teijin Ltd. In partnership with the Tokyo Institute of Technology, it has co-developed a highly conductive carbon nanofibre (CNF) featuring graphene layers, but is yet to develop it for market, explained a spokesperson for the company.

The CNF—which has “the world’s first elliptical cross-section consisting of graphite layers,” according to a company communiqué — has already been designed to be used in battery components and electrode additives, with clear applications for clothing-integrated electronics. The loop-shaped graphene layers promote “chemical reactivity, giving the new CNF higher connectivity with resins and also greater dispersion in liquid substances, properties that have been difficult to achieve with conventional carbon fibres.”

A joint research project between Penn State University, in the United States, and Shinshu University, in Nagoya, has uncovered a method of making strong, stretchable graphene oxide fibres that can be made into yarn, which its study reports claim is of similar strength to Kevlar. The fibre has a high level of electrical conductivity, while being lightweight, which researchers believe makes the yarn suitable for many kinds of highly sensitive sensors.

Meanwhile, in South Korea, researchers at the country’s Electronics and Telecommunications Research Institute and Konkuk University, have coated cotton and polyester yarn with nanoglue and wrapped it in graphene oxide sheets to produce an e-fabric that detects noxious gases and alerts the wearer using an LED light. The new material is particularly effective in detecting nitrogen oxide, which can be dangerous to human health after heavy or prolonged exposure. Researchers report that the new material is suitable for mass production and “can bring a significant change to our daily life.”