Nonmonotonic piezoresistive fibers tuned towards biomechanical sensing

Abstract

Tuning nonmonotonic piezoresistive materials to detect motions within certain strain limits remains an open challenge. In addition, the origin of this unusual form of piezoresistance is still not properly understood especially for semi conducting polymer nanocomposites containing carbon nanotubes. In this work, we report wet spun nanocomposite fibers based on Poly (ether-block-amide) (PEBA) and multiwalled carbon nanotubes (MWCNT) that show differential sensitivity under uniaxial loading. This nonmonotonic piezoresistance is triggered by yielding of polymer segments which later influences the interaction between the embedded MWCNT at higher draw ratios. We confirmed this observation by correlating the stress – strain curve with the resistance – strain response and further studied its influence on the strain sensing phenomena of PEBA / MWCNT fibers. Moreover, pre-stretched fibers at draw ratios slightly above the yield point produced stable and reproducible sensing signals after applying them as biomechanical sensors for motions associated with small bending radii such as finger-wagging.

Keywords

• Piezoresistance
• Strain sensor
• Carbon nanotubes
• Nonmonotonic
• Fibers