A high-sensitivity thin-film MWNT@PDA-AgNP nanocomposite sensor for acquiring microscopic deformations

Carbon nanomaterial/polymer-based flexible strain sensors form the foundations of many cutting-edge applications, e.g., personalized health monitoring, human-machine interaction, etc. However, achieving a high sensitivity to slight deformations remains a challenging task for the existing technologies. Herein, we immobilize silver nanoparticles (AgNPs) onto the surfaces of multi-wall carbon nanotubes (MWNTs) by a polydopamine (PDA)-assisted process, in order to fabricate a new nanocomposite sensor for capturing microscopic static deformations (strain: <1%) and microscopic high-frequency vibrations (strain: <0.001%, frequency: up to 100 s kHz). The material characterizations performed show that AgNPs are compounded, in their elemental state, with the PDA nanolayers on the surfaces of MWNTs, and help to lower the potential barriers between nanofillers. As such, the tunneling of electrons across adjacent nanofillers, which underpins the sensing of slight deformations, is promoted. The proposed nanocomposite sensor demonstrates a significantly higher sensitivity to both static (gauge factor: ∼38) and dynamic deformations, than control specimens that are fabricated from pure MWNTs or PDA-coated MWNTs. Moreover, the sensitivity of the new sensor to microscopic high-frequency vibrations is positively related to the mass of the AgNPs added. This study presents a promising surface modification approach for optimizing the sensitivities of carbon nanomaterial/polymer-based strain sensors to slight deformations.