Foil Strain Gauge Sensors of Piezoresistive Carbon Nanotube Yarn: Fabrication and Calibration

Abstract

Carbon nanotube yarns are micron-scale fibers comprised by tens of thousands of carbon nanotubes in their cross section and exhibiting piezoimpedance characteristics that can be tapped to sense strain. This paper presents the details of novel foil-based strain gauge sensor configurations comprising carbon nanotube yarn. The strain gauge sensors were designed considering parametric studies that maximize the sensitivity of the sensor to mechanical loading. The fabrication details of the strain gauge sensors that exhibit the highest sensitivity, based on the modeling results, are described including the materials and procedures used in the first prototypes. Details of the calibration of the strain gauge sensors are also provided and discussed in the context of the electromechanical characterization when bonded to metallic specimens. This characterization included studying their response under monotonic and cyclic loading. It is shown that these strain gauge sensors consisting of carbon nanotube yarn are sensitive enough to capture strain. Previous modeling results indicated the potential of the strain gauges to exhibit gauge factors higher than those of metallic foil strain gauges.