Nanotech transforms cotton fibres into modern marvel

Juan Hinestroza and his students live in a cotton-soft nano world, where they create clothing that kills bacteria, conducts electricity, wards off malaria, captures harmful gas and weaves transistors into shirts and dresses.

Matilda Ceesay '13, left, drapes muslin on an anti-malarial garment worn by Sandy Mattei '14. / Mark Vorreuter/File photo

''Cotton is one of the most fascinating – and misunderstood materials,'' says Hinestroza, associate professor of fibres science, who directs the Textiles Nanotechnology Laboratory at Cornell. ''In a nanoscale world – and that is our world – we can control cellulose-based materials one atom at a time.''

The Hinestroza group has turned cotton fibres into electronic components such as transistors and thermistors, so instead of adding electronics to fabrics, he converts the fabric into an electronic component.

''Creating transistors and other components using cotton fibres brings a new perspective to the seamless integration of electronics and textiles, enabling the creation of unique wearable electronic devices,'' Hinestroza said.

Taking advantage of cotton's irregular topography, Hinestroza and his students added conformal coatings of gold nanoparticles, as well as semi-conductive and conductive polymers to tailor the behavior of natural cotton fibers.

''The layers were so thin that the flexibility of the cotton fibres is always preserved,'' Hinestroza said, ''Fibres are everywhere from your underwear, pajamas, toothbrushes, tires, shoes, car seats, air filtration systems and even your clothes.''

Abbey Liebman created a dress using conductive cotton threads capable of charging an iPhone. With ultrathin solar panels for trim and a USB charger tucked into the waist, the Southwest-inspired garment captured enough sunshine to charge cell phones and other handheld devices – allowing the wearer to stay plugged in.

Marcia Silva da Pinto, post-doctoral researcher, works on growing metal organic frameworks onto cotton samples to create a filtration system capable of capturing toxic gas, as Juan Hinestroza looks on./ Mark Vorreuter/File Photo

The technology may be embedded into shirts to measure heart rate or analyse sweat, sewn into pillows to monitor brain signals or applied to interactive textiles with heating and cooling capabilities.

''Previous technologies have achieved similar functionalities, but those fibres became rigid or heavy, unlike our yarns, which are friendly to further processing, such as weaving, sewing and knitting,'' Hinestroza says.

Synthesising nanoparticles and attaching them to cotton not only creates colour on fibre surfaces without the use of dyes, but the new surfaces can efficiently kill 99.9 per cent of bacteria, which could help in warding colds, flu and other diseases.

Two of Hinestroza's students created a hooded bodysuit embedded with insecticides – using metal organic framework molecules, or MOFs – to fend off malarial mosquitoes. Malaria kills more than 600,000 people annually in Africa.

While insecticide-treated nets are common in African homes, the anti-malarial garment can be worn during the day to provide extra protection and does not dissipate like skin-based repellants.

Other students have used MOFs to create a mask and hood capable of trapping toxic gases in a selective manner. MOFs, which are clustered crystalline compounds, can be manipulated at the nano level to build nanoscale cages that are the exact same size as the gas they are trying to capture.

''We wanted to harness the power of these molecules to absorb gases and incorporate these MOFs into fibres, which allows us to make very efficient filtration systems,'' he explains.

Hinestroza always looks for new ways to employ cotton as a canvas for creating infinite modern uses.

''We want to transform traditional natural fibres into true engineering materials that are multifunctional and that can be customised to any demand,'' he says. ''We are chemists, we are material scientists, we are designers, we want to create materials that will perform many functions, yet remain as flexible and as comfortable as a t-shirt or an old pair of jeans.''