Investigation of strain sensing mechanisms on ultra-thin carbon nanotube networks with different densities

Transparent, highly stretchable and sensitive strain sensors have been successfully fabricated using carbon nanotube (CNT) networks with various densities as the sensing medium. Owing to the unique two-dimensional percolated structure, the CNT network-based sensors exhibit excellent sensing performance over a wide strain range from 0.5 to 100%. By decreasing the density of CNTs from 152 to 7.2/μm2, their gauge factor is remarkably increased from 0.4 to 50. It is found from the experimental results and theoretical analysis that the sensing mechanism of the CNT networks is transferred from percolation theory to tunneling effect with decreasing the density or increasing the tensile strain of the CNT networks. This study provides a facile technique to prepare high stretchable strain sensors and also fundamental principles for the structural design of the CNT network-based strain sensors.