Smart Fibers Based on Low Dimensional Conductive Materials

The fragility of traditional metallic or semi-conductive materials hinders their application in flexible electronics. Low dimensional materials including carbon nanotubes, graphene and metal nanowires own outstanding flexibility and have been wildly used to fabricate flexible devices. Bendable/stretchable substrate is another key component of flexible electronics. Various thin polymer films made of polyethylene terephthalate, polyimide, polydimethylsiloxane et. al. were adopted. However, the air impermeability of these substrates will cause discomfort of humanbeing if applied in wearable electronics. Fiber is an ideal substrate for flexible and wearable electronics due to its excellent flexibility/stretchability, superior breathability, abundant microstructure and low cost. Herein, a series of conductive elastomers and strain sensors were fabricated by combining the low dimensional conductive materials with fiber substrates and regulating the microstructure on the interface. With the help of “twining spring” hierarchical architecture, silver nanowire-double covered yarn (Ag NW-DCY) composite fibers with ultrahigh stretchability were obtained. The conductivity of the composite fibers reached up to 104 S/cm and remained 90% at 2000% tensile strain. Commercial electronic components (LED arrays) were integrated onto a transparent, foldable and stretchable substrate using the composite fibers as stretchable electric wiring, demonstrating the potential application in large-area stretchable electronics. When AgNWs were replaced with graphene, strain sensing fiber with high sensitivity and large working range (100% strain) were fabricated, which enabled the detection of multiple deformation forms, including tensile strain, bending, and torsion. We employ the fibers as wearable sensors, realizing the monitoring of full-range human activities and intricate movement combinations of a robot. Besides, these fibers exhibits fast response, low hysteresis and excellent cycling stability. Another advantage needs to be noted is that these fiber are fabricated by a facial dip coating method, which can be scaled up easily. These smart fibers are of great meaning to the development of flexible and wearable electronics.