Topological Design and Characterization of Piezoresistive Nanocomposites

Abstract

Piezoresistive nanocomposites have been extensively studied because of their broad applicability for various sensing applications (e.g., monitoring structural integrity and human performance). The piezoresistivity of many polymer nanocomposites stems from conductive/semi-conductive nanofillers’ intrinsic piezoresistivity, tunneling effect, and contact resistance changes of the nanofiller networks as they are strained. Although various nanocomposite strain sensors have been developed using different material systems and manufacturing techniques, their empirically guided fabrication approach can be laborious, inefficient, and, most importantly, unpredictable. Therefore, this study proposes a topological design-based methodology to strategically manipulate the strain sensing performance of these nanocomposites to achieve a wide range of optimized strain sensitivities using the same material system. To demonstrate this, carbon nanotube-latex nanocomposite thin films were spray-fabricated onto patterned polyethylene terephthalate substrates pre-designed with stress-concentrating and stressreleasing topologies. The strain sensing performance of nanocomposites of different topologies was characterized and compared. Furthermore, the mechanical and electromechanical properties of the thin films were also characterized using numerical models. Both the experimental and computational results indicated that the stressconcentrating topologies could enhance strain sensitivity, whereas the stress-releasing topologies significantly suppressed bulk film piezoresistivity.