Researchers at Stanford University in the US have discovered a highly elastic, transparent thin film that conducts electricity extremely well. The film is made of wavy, spring-like carbon nanotubes.
Making the film
The researchers made the transparent elastic films by airbrushing a solution of carbon nanotubes onto the top and bottom surface of a flat silicone sheet. After coating, the researchers stretched the sheet and made to relax so that the nanotubes naturally formed wavy, spring-like structures. The researchers claim that this is the first stretchable, transparent, skin-like sensor so far made with or without carbon nanotubes.
Working
The set-up behaves like a capacitor, with the silicone layer storing electrical charge. When pressure is applied to the sensor, the silicone layer compresses and alters the amount of electrical charge that it can store. When the composite film is stretched again, the nanotubes straighten out in the direction they are stretched. The film can be stretched up to two and half times its initial length in any direction without damage, always reverting back to its original dimensions, even after many stretches. The electrical conductivity of the thin film does not change as long as the material is not stretched beyond the initial stretch amount.
Applications
This device can be used to restore touch and pressure sensitivity to amputees, injured soldiers and burn victims, and also for applications in robotics and touch-sensitive computer displays. It can be used as the electrode material in "skin-like" pressure, force and stretch sensors. The film might find applications in screens for mobile devices that can sense a range of pressures. Applications also include sensors for touch screens that are collapsible, stretchable and virtually indestructible, transparent electrodes for solar cells that could be wrapped around the curved surfaces of vehicles and buildings without wrinkling, and sensors for robots and artificial intelligence systems.
Other applications include 'smart' steering wheels that could sense if the driver was falling asleep which give 'biofeedback'. Artificial skin made from the material might also be used to restore the sense of touch to amputees when fitted with prosthetic limbs covered with the skin, injured soldiers and burn victims.
The researchers claim that in the future, it should also be possible to use these films to design organic, skin-like devices with the ability to sense moisture, temperature, light and even chemical and biological species. They would also like to integrate the skin-like pressure sensors with neurons, as well as try out the electrodes in solar cells.