Characterizing the spatial piezoresistivity tensor for inkjet-printed carbon nanotube thin film sensors
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ASME Conference on Smart Materials, Adaptive Structures and Intelligent Systems 2017
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Inkjet printing is currently a popular technique offering cheaper ways to assemble nanoparticles into complex patterns. Carbon nanotubes (CNT) exhibit outstanding mechanical and electrical properties that can be dispersed into an aqueous ink solution, which can be inkjet-printed over flexible substrates to perform multifunctional tasks such as sensing, actuating, or LED displaying. These printed thin films consist uniform morphology and consistent electrical properties; while subjected to loading, their electrical responses can be correlated to parameters of deformation, such as strains. Some previous studies have characterized the 1-dimensional strain sensitivity of CNT-embedded nanocomposites as a strain gage, but it remains unknown how their electrical responses can be correlated to the strain state in a spatial mean. In this study the 2D piezoresistivity of an inkjet-printed sample over transparency substrate is characterized via a monotonic tensile loading test. While loaded the voltage response of a printed rectangular shape is taken to perform resistivity calculation using the Montgomery method. The resistivity-strain constitutional relation of an inkjet-printed CNT thin film is established based on theories for semi-conductive materials. In the end the fourth-order tensor matrix characterizing the spatial piezoresistivity of the CNT thin film is formulated and calculated.