Flexible Carbon Nanotube Sensors with Screen Printed and Interdigitated Electrodes

Printed electronics is a rapidly emerging field due to the development of new types of functional materials and inks that can be deposited using well-known and widely established printing techniques. Commonly, sensor structures or interconnects on printed circuit boards (PCBs) are fabricated using wet etching and photolithography steps. To overcome the limitations of those techniques, in this contribution, we use a simple and scalable screen printing process to deposit silver-flake based interdigitated electrode (IDE) structures onto sprayed carbon nanotube (CNT) films. The silver (Ag) structures show a low sheet resistance and resistivity of 0.14 Ω/sq. and 6.1·10
^-7
Ω·m, respectively, at a thickness of around 4.4 μm. Attributed to its flexibility and robustness, a polyimide foil (Kapton®HN) was selected as the substrate. The CNT films with printed IDE that are entirely fabricated in the ambient air are then characterized as resistive gas sensors to detect ammonia (NH
₃
). A high response of around 20% is achieved for an NH
₃
concentration of 50 ppm.