Conformable Carbon Nanotube Thin Film Transistors on Ultrathin Flexible Substrates

Abstract

Skin-like electronics that enable robust, intimate, and comfortable contact for direct biotic/abiotic interface are highly expected in next-generation wearable clinical and biological technologies. Carbon nanotubes (CNTs) have emerged as one of the leading candidates of flexible semiconducting materials due to their high carrier mobility, mechanical flexibility, and solution-processed fabrication, which could make important contributions to skin-like electronics. In this work, incorporating device fabrication on ultrathin substrate ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.4 \mu \text{m}$ </tex-math></inline-formula> thick) and capillary-assisted electrochemical delamination (CAED) process, CNT-based thin film transistors (TFTs) were realized with great conformability to biological surfaces, even contacting with the ridges and valleys on human fingertips. Excellent flexibility was also achieved with little performance degradation of CNT TFT after being deformed by bending or wrapping onto human hairs. The CNT TFT on ultrathin substrate demonstrates good electrical properties with mobility of 23 cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{{2}}\text{V}^{-{1}}\text{s}^{-{1}}$ </tex-math></inline-formula> , current ON- OFF ratio of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{{5}}$ </tex-math></inline-formula> , and subthreshold swing of 109 mV/dec. A flexible amplifier was constructed based on the CNT TFTs with a low voltage supply (±1 V) and wide bandwidth (3.7 kHz). Such simultaneously achieved great conformability, low-voltage supply, and wide bandwidth of the flexible amplifier provide important capabilities and opportunities for CNT-based electronics in future advanced biological or clinical applications.