Oxide Thin-Film Transistors on Fibers for Smart Textiles

Smart textiles promise to have a significant impact on future wearable devices. Among the different approaches to combine electronic functionality and fabrics, the fabrication of active fibers results in the most unobtrusive integration and optimal compatibility between electronics and textile manufacturing equipment. The fabrication of electronic devices, in particular transistors on heavily curved, temperature sensitive, and rough textiles fibers is not easily achievable using standard clean room technologies. Hence, we evaluated different fabrication techniques and multiple fibers made from polymers, cotton, metal and glass exhibiting diameters down to 125 μm. The benchmarked techniques include the direct fabrication of thin-film structures using a low temperature shadowmask process, and the transfer of thin-film transistors (TFTs) fabricated on a thin (≈1 μm) flexible polymer membrane. Both approaches enable the fabrication of working devices, in particular the transfer method results in fully functional transistor fibers, with an on-off current ratio >107, a threshold voltage of ≈0.8V, and a field effect mobility exceeding 7 cm2 V−1 s−1. Finally, the most promising fabrication approach is used to integrate a commercial nylon fiber functionalized with InGaZnO TFTs into a woven textile.