Design and development of ultra-sensitive, dynamically stable, multi-modal GnP@MXene nanohybrid electrospun strain sensors

Electrospun fiber-based strain sensors are widely used in biomonitoring due to their network construction and tailorable design. However, poor cycling stability and lack of multi-modality remain major issues. In this study, a 3-component material system consisting of MXene, graphene nanoplatelets (GnPs), and cellulose nanocrystals (CNCs) was employed to address multi-modality and sensitivity shortcomings. The hybrid synergetic interactions between MXene and graphene nanoplatelets (GnPs) provided high gauge factors (400 at 100% and 76.1 at 10% strains). Smaller and more conductive MXene particles provided higher electrical conductivity and sensitivity at lower strain ranges (with a low detection limit of 0.25% and a short response time of 100 ms) by forming localized brittle regions. Synergistically, GnP flakes with large laterial sizes promoted network connectivity, easy sliding across larger strains, and lubricity. On the other hand, the CNC binder enhances the uniformity and interfacial hydrogen bonding between the constituents, leading to desirable cycling capabilities for over 2,000 cycles. An in-situ ultrasonic atomization process was used to decorate the poly(styrene-butadienestyrene) (SBS) substrate with the electrically conductive additives, which remarkably enhanced the uniformity of the conductive coating. With the simultaneous vacuum-assisted filtration, this technique provided more conformal and in-depth fiber decoration, promoting multi-modality and sensitivity. The developed strategies proved to be effective in creating sensors with ideal body integration and successful recording of various body motions.