Intrinsically flexible thickness sensor system made of coil-shaped carbon nanotube-filled polymer composite

To perform measurements in special environments like narrow gaps, a coil-shaped carbon nanotube composite is structured as a sensing element. Its high conductive phase ratio offers superior response to magnetic field changes, outperforming traditional metals in non-contact magnetic sensing. The composite's feasibility for magnetic flux thickness measurement is validated through experiments, leading to the design of a thickness measurement and material discrimination system for real-time monitoring by an upper computer. The carbon nanotube composite can reach the sensitivity (65.32   mV/mm in planar, 63.54   mV/mm in curved) as traditional metal (69.8842   mV/mm). The flexible sensor system can maintain a high accurate measurement under curved conditions with the highest accuracy of 0.879% planar and 0.157% curved. This paper replaces traditional metal materials with the composite for non-contact thickness measurement and material discrimination in curved narrow gaps, offering a practical measurement system and a reference for using flexible composite materials with sensing and measurement capabilities in special environments.