Interfacial instability in confined multi-channels inspired by the cuttlebone

An interface in a confined channel becomes unstable when a viscous fluid is displaced by a less viscous fluid. Suppressing such interfacial instability plays a key role in many petroleum industries and biological systems.  One natural example is to push a gas-liquid interface inside the cuttlebone. The structure is made of multiple parallel microscopic chambers, which are reinforced by vertical wall-like structures with wavy cross-sectional profiles. In this study, we investigate the interfacial dynamics in multi-channel structures, inspired by the cuttlebone, and their ability to suppress the instability of the moving liquid-gas interface. The instability of a liquid-gas meniscus for different flow rates, channel curvatures, and arrangements has been studied through combined experimental and theoretical approaches.  Results show that the curvature can prevent the uneven growth of the menisci inside channels, helping to transport the liquid-gas interface more uniformly. Due to the channel arrangement and the slow motion of the interface, the Saffman–Taylor instability is suppressed, resulting in the efficient process of pumping a liquid in and out of multi-channels. Such a complex structure (e.g. cuttlebone) can inspire a new design for microfluidics platforms.