Fabrication of serpentine and I structured graphene-CNT based highly sensitive and flexible strain sensors

Abstract

Carbon based nanomaterials are frequently used for the fabrication of flexible electronic devices in past few years. Graphene and carbon nanotubes (CNTs) are the carbon nanomaterials known for their superior and adaptable properties to be used as a conductive filler in flexible sensors. In this work, graphene/CNT composite based strain sensors were fabricated on polymer substrate by using a simple fabrication technique. Conductive thin film of the graphene/CNT composite was formed and designed into two different structures i.e. ‘I' and ‘Serpentine’ to enhance the sensing performance of the film. The electrical performances were observed in the form of I-V characteristics and the resistive behavior of all the fabricated samples are reported. For both cases, significant variation in relative resistance was observed during bending of the sensors at various radius of curvature. The relative variation of resistance in serpentine structured samples were significantly high in comparison to ‘I' structured samples. The sensitivity was defined by the measurements of relative resistance variation against level of strain from 0.1% to 0.6% and a gauge factor of 67 and 96 was observed for ‘I' and ‘Serpentine’ structures respectively. To demonstrate the potential application, the fabricated sensors were implemented for the measurements of finger movements at various angles (from 00 to 900) and significant change in resistance of the sensors were observed. The durability of the fabricated sensors were tested over 1000 cycles at a strain of 0.3%.