Highly sensitive flexible strain sensor based on threadlike spandex substrate coating with conductive nanocomposites for wearable electronic skin

Electronic skin (e-skin) with favorable wearability and high flexibility has increasingly raised attention for potential research prospect in artificial skin, flexible electronics, soft robotics and prosthetic device. A flexible resistive strain sensor with layered structure made up of Graphene nanoplatelets (GNPs) layer and GNPs/polyaniline (PANI) synergetic conductive network based on threadlike spandex substrate is successfully fabricated by a simple layered dipping-drying process. Herein, the fiber-based strain sensors with high sensitivity (the gauge factor calculated at 0%–15% and 15%–30% is ∼6.8 and ∼60.3, respectively), lower detection limit, long-term stability and durability (∼1000 cycles), fine repeatability and low temperature dependence was prepared through designing layer-by-layer structure and synergetic conductive network. And the biocompatible and breathable e-skin device could be prepared by integrating the sensor with semipermeable membrane. The fabricated device can be utilized in detecting small scale human motions, including muscle contraction, relaxation and respiratory movement in different states. Furthermore, a simple facial expression sensing and monitoring application was realized. The spandex-based flexible strain sensor with favorable performance and facile preparation procedure will open potential prospects for wearable e-skin in human motion detecting, physiological sensing and emotional monitoring.