Preparation Of Conductive Polymer Nanofiber Membrane And Its Strain Sensing Performance

Wearable strain sensors are widely applied in flexible electronics,biomedical monitoring,and other fields.Flexible conductive polymer nanofiber composites are good candidates for high performance wearable strain sensors because of their good skin affinity,unique porous structure and thus excellent air permeability.In this study,graphene is assembled on the surface of polymer nanofibers under the assistance of ultrasonic treatment,and thus a flexible conductive polymer nanofiber composite membrane is obtained.The surface modification and structure designation are conducted to endow the nanofiber composite with superhydrophobicity.The relationship between microstructures and properties of the finally obtained nanofiber composite is invesgated in detail.The strain sensing performance and its working mechanism are also explored.This paper mainly includes the following three parts:1.Electrospun thermoplastic polyurethane(PU)nanofibers were first decorated by graphene through ultra-sonication,followed by polydopamine(PDA)modification and then hydrophobic treatment with 1H,1H,2H,2H-perfluorodecanethiol(PFDT).The obtained electrical conductive polymer nanofiber composites(CPNCs)have a hierarchical polymer core/graphene shell structure and exhibit super-hydrophobicity even under harsh environments.The introduction of PDA not only improves the interfacial interaction between individual graphene sheets but also the interaction between graphene and the PU nanofibers.Their mechanical properties including Young's modulus,tensile strength and elongation at break are significantly improved,compared to those of PU nano-fibrous membranes.When CPNC is used as a strain sensor,it displays high stretchability,controllable sensitivity,excellent cyclical stability and durability.Hence,the nanofiber composite based strain sensor can be attached on the skin for precise monitoring of different human motions,such as tiny and large body movements and thus it has promising applications in wearable devices.2.A superhydrophobic and conductive nanofiber composites(SCNCs)with a hierarchical SiO2/graphene shell and polyurethane(PU)nanofiber core microstructure were fabricated by assembling graphene on PU nanofibers under the assistance of ultrasonication,followed by stretching-induced SiO2 nanoparticles decoration onto the graphene shell.Both graphene and SiO2 nanoparticles make contribution to the improvement of the mechanical properties of PU nanofiber membrane.The superhydrophobicity and conductivity are almost maintained after the SCNCs are subject to cyclic stretching or abrasion or even exposed to harsh conditions.The SCNCs-based strain sensor possesses high stretchability and dispalys good reliability when it experienced cyclic stretching test.When used in harsh environment,it also shows excellent durability.The SCNCs can also monitor full range body motions including both subtle and large body movements,making it a promising candidate in wearable electronics.3.The graphene was successfully assembled onto the surface of the pre-stretching PU nanofiber membrane by ultrasonication treatment,and the wrinkled graphene with a unique‘petal-like' structure was finally obtained when the stretched graphene/PU nanofiber composite was released.The preparation is simple and facile without complicated procedures.The introduction of graphene not only endows the nanofibers with conductivity,but only improves the material hydrophobicity.When used as a strain sensor,it exhibits excellent strain sensing performance,with high guage factor and good cycling stability.