Researchers at Berkeley Lab have produced uniform, high performance transistors on mechanically flexible, stretchable substrates by solution processing semiconductor-enriched single wall carbon nanotube (SWNT) networks.
The research team obtained high performance thin film transistor arrays with superb electrical properties (mobility of approximately 20 square centimeters per volt-second and an on/off electrical current ratio of approximately 10,000) on polyimide substrates made flexible by laser cutting a honeycomb mesh structure. The technology, demonstrated on areas as large as 7.5 square centimeters, yields minimal variation from device to device. The Berkeley Lab invention could be combined with inkjet printing of metal contacts for lithography-free fabrication of low cost flexible and stretchable electronics.
Attempts to use other materials to develop flexible electronics have presented challenges. For example, organic materials have demonstrated low performance due to their high operating voltage requirement. SWNTs, attractive candidates given their high carrier mobility, high chemical stability and high bendability, among other desirable mechanical properties, have, until only recently, posed challenges in fabricating devices with high on/off current ratio.