Carbon Nanotubes (CNT) based chemiresistors are one of the fundamental building blocks of the advanced nanosensors for applications in gas sensing and biosensing. Low-temperature fabrication process allows to develop large area flexible sensors for different applications such as environment pollution monitoring, gas leakage, food quality, smart textile, biosensing etc. These sensors are flexible, lightweight and affordable which are requisite properties for large area electronics. Carbon nanotubes have been extensively investigated for flexible electronics application. Different research groups have demonstrated the fabrication of flexible gas sensors and biosensors. In the past, at CSIR-CEERI, SWCNT-based nanosensors have been fabricated on conventional silicon substrates and demonstrated for sensing ammonia gas and humidity. Attempts have been made to fabricate flexible chemiresistors of functionalised singlewalled carbon nanotubes (f-SWCNT).

Polytetrafluro Ethylene (PTFE) sheets were used as flexible substrates. Interdigitated molybdenum metal masks were fabricated using WEDM technique in institute’s workshop. Interdigitated metal electrodes were fabricated on PTFE substrate by depositing Cr and Au through the metal mask by sputtering.

SWCNT chemiresistors were fabricated (Fig. 1) by drop-casting small volume, (few μL) of COOH functionalised SWCNT dispersion using micropipette and drying. I-V measurements were carried out in a temperature range from 25oC to 120oC. Current-Voltage characteristics of fabricated flexible chemiresistor are shown in Fig. 2. Measured resistance value is 59 Ω at room temperature.

Fig. 1: (a) Polytetrafluro Ethylene sheet fixed in Moly mask for Cr/Au deposition by sputtering (b) fabricated flexible SWCNT chemiresistor

Fig. 2: Measured I-V characteristics of flexible chemiresistor at different temperature ranges