Graphene welded carbon nanotube crossbars for biaxial strain sensors

Aligned carbon nanotube (CNT) arrays are promising candidates for strain sensors owing to their scalable preparation and excellent conductivity and stretchability. However, aligned CNT arrays are limited by low strain sensitivity and buckling deformation. In addition, cross-stacked CNT array films layer-by-layer assembled on soft substrates exhibit anisotropic mechanical behavior due to their asymmetric layered structures. In this work, we introduced a chemically hybridized CNT-graphene (G/CNT) film in which CNT crossbars are effectively welded together by graphene. The hybrid films demonstrate enhanced isotropic mechanical properties and strain sensitivity with a gauge factor of similar to 3, together with a high stretchability of more than 20%. The enhanced electromechanical properties are attributed to the improved load transfer efficiency among CNTs by graphene hybridization, as confirmed by Finite Element Analysis (FEA). Biaxial strain sensors based on the hybridized G/CNT films have been applied for sensitive detection of both minute vibrations caused by sound waves and large deformations from finger bending. The sensors were further integrated into a tactile sensing array to map the spatial distribution of the surface pressures. (C) 2017 Elsevier Ltd. All rights reserved.