Insight into the Effect of Structural Geometric Design on the Sensitivity of Magnetic Strain Sensors

Herein, a win-win design concept and novel strategy for structural geometric design have been proposed to improve the sensitivity of magnetic strain sensors. The proposed scheme utilizes the metal catalyst embedded in single-walled carbon nanotubes (SWCNT) to enhance magnetic induction characteristics and reduce purification costs. Magnetic properties of the materials were realized by embedding permalloy particles into SWCNT using arc-discharge technique, and the magnetic characteristics, structure, and morphology of the composite material were optimized via heat treatment and thermal reduction. To improve the sensitivity, a structural geometric design with triangle-shaped sensors has been proposed, which involved two configurations of directional increase in length or the expansion of inner angles. The latter had a larger impact on sensitivity improvement than the former. Fiber/line-shaped sensors with different constant diameters were prepared to demonstrate the effectiveness of the proposed strategy on the sensitivity. The comprehensive analysis demonstrated that triangle-shaped sensors with a 1:11 width ratio between the two ends exhibited a high sensitivity (gauge factor = 28.2 at 50–80% strain), high stretchability (100%), outstanding durability (1000 r), high saturation magnetization (4.8 emu g -1 ), and fast response time. Excellent durability was determined by tracking morphological evolution. The as-fabricated sensors can be used in power switches and electromagnetic shielding applications as well as to monitor the weight of light objects and displacement changes.