Confined Water-Assistant Thermal Response of a Graphene Oxide Heterostructure and Its Enabled Mechanical Sensors for Load Sensing and Mode Differentiation.

Mechanically responsive features are essential in devising mechanical sensors capable of sensing and differentiating loadings. We present a heterostructure composed of bilayer graphene oxides and confined water as a mechanical sensor that enables the detection and differentiation of tension, compression, pressure, and bending. Guided by molecular simulations, we demonstrate that the thermal transport across solid-liquid interfaces is sensitive to loading modes owing to the reversible response of hydrogen-bonding networks between confined water molecules and graphene oxides and quantitatively elucidate the thermal transport mechanism by correlating the thermal conductance, number, and distribution of hydrogen bonds and interfacial energy with mechanical loadings. Such structure-enabled mechanical sensor with contrasting thermal response to different loading modes is devised to exemplify the robustness of sensing functions. These results lay a foundation for rational designs of mechanical sensors that leverage the thermal response of solid-liquid systems beyond the current strategy relying on the electrical properties of sole solids.