A study of the interactions of carbon based fillers in acrylonitrile butadiene rubber matrix for high deformation sensor applications

A strain sensor was prepared by reinforcing acrylonitrile butadiene rubber (NBR)-5 parts per hundred of rubber (phr) carbon black (CB_H) separately with small concentration (∼0.1phr) of reduced graphene oxide (G_L), multi-walled, and carbon nanotube (NT_L) via a combination of conventional solution and solid processing techniques. The interactions and the electronic properties among carbon based fillers NT, CB, G and their synergy effects (NBR-CB_H-G_L and NBR-CB_H-NT_L) were investigated by using density functional theory (DFT) modeling approach. The DFT predictions were in correspondence with the experimental results. The optimum design (NBR-CB_H-G_L) was found to show high curing, mechanical and improved electrical properties. On account of strain sensing performance, NBR-CB_H-G_L exhibited high gauge factor (GF) ∼10⁵ at 0–40% strain, which was over 900% than NBR-CB_H (GF ∼10⁴ at 0–30% strain) and the highest reported so far. This was explained by the breaking of CB networks caused by tight NBR-G structures on straining, leading to high electrical resistance. The NBR-CB_H-G_L also demonstrated high stability and repeatability in the cyclic loading. In terms of applications, NBR-CB_H-G_L exhibited high capability for vibration detections and wearable sensing, especially for detection of human bodily motions like speeches, facial deformations, bending, and relaxation of the fingers.