Printed, Sub-3V Digital Circuits on Plastic from Aqueous Carbon Nanotube Inks

TLDR

Printing electronic components on plastic foils with liquid inks offers flexible, low‑cost circuitry, but slow switching and high supply voltages limit widespread use. The study aims to demonstrate fast, flexible digital circuits by combining printable high‑capacitance dielectrics with high‑mobility carbon‑nanotube semiconductors. The authors fabricated ion‑gel‑gated CNT thin‑film transistors with 50 µm channels, achieving ambipolar mobilities >20 cm²/V·s, and used them to print inverters, NAND gates, and ring oscillators on polyimide and SiO₂ substrates. Five‑stage ring oscillators reach >2 kHz at 2.5 V, with 50 µs stage delays, marking a substantial improvement over prior printed circuitry from liquid inks.

Abstract

Printing electronic components on plastic foils with functional liquid inks is an attractive approach for achieving flexible and low-cost circuitry for applications such as bendable displays and large-area sensors. The challenges for printed electronics, however, include characteristically slow switching frequencies and associated high supply voltages, which together impede widespread application. Combining printable high-capacitance dielectrics with printable high-mobility semiconductors could potentially solve these problems. Here we demonstrate fast, flexible digital circuits based on semiconducting carbon nanotube (CNT) networks and high-capacitance ion gel gate dielectrics, which were patterned by jet printing of liquid inks. Ion gel-gated CNT thin-film transistors (TFTs) with 50 μm channel lengths display ambipolar transport with electron and hole mobilities >20 cm2/V·s; these devices form the basis of printed inverters, NAND gates, and ring oscillators on both polyimide and SiO2 substrates. Five-stage ring oscillators achieve frequencies >2 kHz at supply voltages of 2.5 V, corresponding to stage delay times of 50 μs. This performance represents a substantial improvement for printed circuitry fabricated from functional liquid inks.