Researchers at the University of California at Berkeley have made high-performance integrated circuits on flexible substrates from thin-film transistors containing semiconductor-enriched carbon nanotubes.
Flexible electronics
Flexible electronics has made considerable progress in the last few years using various types of semiconductor materials such as organic semiconductors, silicon with a buckling structure, carbon nanotubes, inorganic nanowires and metal oxides.
Carbon nanotubes
The materials for the flexible circuits should be easy and cheap to process at room temperature and have high charge-carrier mobility. Thin films of carbon nanotubes are found to be ideal in this respect as researchers have already made sophisticated integrated flexible circuits, including flip-flops and decoders, using carbon nanotubes directly grown by chemical vapor deposition.
Nanotube thin films
Researchers used purified semi conducting-only carbon nanotube ink for fabricating integrated circuits on mechanically flexible substrates compatible with large-scale roll-to-roll printing processes. The technology is simple, scalable, low-cost, and robust and produces highly reproducible and uniform transistors with good performance.
Researchers have made nanotube thin films using a room-temperature drop-casting process to make structures with uniform high density of nanotubes throughout the sample to get transistors with very small device-to-device variations. Unlike organic semiconductor materials, these devices are not sensitive to oxygen or moisture.
Applications
Semiconductor-enriched carbon nanotubes find applications in displays, electronic skin, wearable devices and medical prostheses. Other applications are in electronic skin, robotics, flexible active-matrix backplanes for display and sensor applications, circuits that can directly integrated with multifunctional sensor arrays for on-chip signal processing and wireless data transfer.
The devices made by these materials are highly flexible so that they can be bent and unbent a number of times without suffering any damage.