A bioinspired multilayer assembled microcrack architecture nanocomposite for highly sensitive strain sensing

Despite the wide applications of strain sensor in wearable devices and electronic skins, the poor flexibility, low sensitivity and repeatability, as well as the utilization of noxious agents dramatically restrict its large-scale application. Herein, a simple and efficient strategy is demonstrated to fabricate flexible, ultrahigh sensitive and reproducible strain-sensing platforms via an eco-friendly water-based layer-by-layer assembly method. Specifically, renewable and biocompatible cellulose nanocrystals with electronegativity were used as the stabilizer to disperse multiwall carbon nanotubes (MWCNTs), meanwhile chitosan solution with rich positive charges was used as the effective “gluing” to enhance the interaction force between the monolayer MWCNTs. The resulting multilayer cracking-structured nanocomposites exhibited ultrahigh sensitivity with a gauge factor ∼359 and detection limit of ε = 0.5%. The samples maintained similar sensitivity even after 200 cycles of stretching/releasing. The high sensitivity is attributed to the disconnection-reconnection of the bioinspired spider-like microcrack junctions in MWCNTs layer. Moreover, the obtained strain sensor showed the abilities to detect not only large-scale body motions (finger bending) but also small-scale physiological strains induced by minute movements of muscles upon swallowing and smiling. It is promising to integrate this kind of strain sensors with human beings in future wearable devices and electronic skins.