Instrumentation: astronomers look to nanotechnology.

nature nanotechnology | VOL 3 | AUGUST 2008 | www.nature.com/naturenanotechnology 459 and protective shell. The nanoscale and hydrophobic structures of the network enable the otherwise water-absorbing cotton to repel water nearly as efficiently as the lotus leaf. Furthermore, the treated fabrics are stronger and more resistant to tears. Nanotube concentrations of over 2% in the applied emulsion made it more difficult for the cloth to catch fire and prevented burning by forming a carbonaceous amorphous char on the surface of the cotton, which behaved as a heat shield. With just 0.25% of nanotubes, more than 90% of the harmful ultraviolet rays that would normally penetrate an untreated fabric could be blocked. Strong fabrics with ultraviolet resistance and water-repellent properties may offer new alternatives to soft linings in marine and outdoor applications. Furthermore, cotton fabrics coated with nanotubes that are modified with enzymes capable of detecting and detoxifying chemical warfare agents could offer a new line of comfortable chemical protective clothing for the military and civilian first responders3. Textiles coated with nanotubes modified with other enzymes may also be used to make drug-impregnated gloves for arthritic patients or be used as a bed lining for transdermal drug delivery while a person sleeps on it. The reported results are impressive and future studies using highly pure nanotubes with a specific set of well-characterized electrical, chemical and physical properties will offer a myriad of tailor-made applications. If the electronic properties of the nanotubes on the surface of the cotton can be harnessed, it will be possible to design wearable sensors or to build power generators and energy storage capabilities into the clothing. For example, the piezoresistance properties of nanotubes may be used to detect variations of electrical conductance as a function of mechanical deformation of the fabrics. This could be used to monitor the motion of muscles and limbs for rehabilitative and telemedicine applications. Because chirality (or handedness) of nanotubes defines whether they are metallic or semiconducting, it is possible to engineer fabrics that are either insulating or conducting. If a single layer of nanotubes can be deposited around the cotton fibre, the configuration of an insulating fibre located directly underneath a conductive layer may be exploited to fabricate flexible transistors4. Multilayering, on the other hand, may allow high rates of conduction with low rates of heat dissipation, making low-power wearable electronics a closer reality5. The reported results are of great interest and further studies are needed to understand the mechanisms responsible for the improved properties. The synergy between a flexible renewable natural substrate such as cotton and the increasing multifunctionality of nanotubes offers an endless number of possibilities. Perhaps one day it will allow us to dress like superheroes.