Enhancing Piezoresistive Bending Strain-Sensing Performance of MoS2 Films through a Composite with Cobalt Phthalocyanine

Abstract The growing demand for flexible, wearable strain sensors for smart electronics, human physiological monitoring applications, etc. necessitates development of sensors with high sensitivity and with simple fabrication methods suitable for large-scale production. In this study, bending strain sensors were fabricated using MoS2/CoPc nanocomposites that were synthesized through a simple solution route, and their response to bending strain was found to be higher than that of pristine MoS2 film-based strain sensors. Investigation of the films using various characterization techniques revealed the presence of tensile and compressive stress on both the materials in the nanocomposite films, due to mutual influence among them, and indicating intimate contact between them. An increase in tunneling and contact resistance due to the presence of less conducting CoPc molecules between the agglomerated bunches of highly conducting MoS2 nanosheets, as well as weak van der Waals interaction-assisted slippage of MoS2 nanosheets and CoPc molecules, is suggested to play an important role in improving the response of the nanocomposite film sensors. An improved response with good repeatability in performance was obtained for an optimum quantity of CoPc in the nanocomposites. Generation of large cracks in the nanocomposite films for CoPc quantity beyond this optimum value leads to an irreversible increase in resistance and hence prevents repeatability in bending strain-sensing measurements. Monitoring of various human physiological movements and verification of quality of food items were demonstrated using the best performing nanocomposite film-based sensors.