Hybrid Integration of Carbon Nanotubes and Transition Metal Dichalcogenides on Cellulose Paper for Highly Sensitive and Extremely Deformable Chemical Sensors

Sensitive and deformable chemical sensors manufactured by a low-cost process are promising as they are disposable, can be applied on curved, complex structures, and provide environmental information to users. Although many nanomaterial-based flexible sensors have been suggested to meet these demands, their limited chemical sensitivity and mechanical flexibility pose challenges. Here, a highly deformable chemical sensor is reported with improved sensitivity that integrates multiwalled carbon nanotubes (CNTs) and nanolayered transition metal dichalcogenides (TMDCs) on cellulose paper. Liquid dispersions of CNTs and TMDCs are absorbed and dried on porous cellulose for sensor fabrication, which is simple, scalable, rapid, and inexpensive. The cellulose substrate enables reversible three-dimensional folding and unfolding, bending down to 0.25 mm, and twisting up to 1800° (∼628.4 rad m^–1) without degradation, and the CNTs maintain a percolation network and simultaneously provide gas reactivity. Functionalization of CNTs with TMDCs (WS₂ or MoS₂) greatly improves the sensing response upon exposure to NO₂ molecules by more than 150%, and the sensor can also selectively detect NO₂ over diverse reducing vapors. The measured NO₂ sensitivity is 4.57% ppm^–1, which is much higher than that of previous paper-based sensors. Our sensor can stably and sensitively detect the gas even under severe deformation such as heavy folding and crumpling. Hybrid integration of CNTs and TMDCs on cellulose paper may also be used to detect other harmful gases and can be applicable in low-cost portable devices that require reliable deformability.