Lubricant depletion and interface dynamics in liquid-infused microchannel subjected to external oscillations

Abstract

Lubricant-infused surfaces (LIS) find suitability in a plethora of applications due to their omniphobic functionalities. LIS, however, lose their functionality in the absence of the lubricant. A majority of the studies have focused on understanding the liquid-repellent properties of LIS, but only limited attention has been paid to understanding their durability. In this work, we focus on the interface dynamics for prolonging the durability of LIS during transport for food packaging applications. We analyze the lubricant retention characteristics within cavities when subjected to pure oscillations (zero net flow). The microchannel is excited at f = 0.1 - 10 Hz for viscosity ratio ( μ r = 0.4 - 1.0 and μ r = 1.8 ) for a dovetail cavity with lubricant of two different densities. The failure and stability of LIS are characterized based on the orientation of velocity vectors and the position of vortex formed within the cavity. A random orientation of velocity vectors within the cavity signifies failure of LIS. External oscillations cause the interface to rupture and form drops. Upon rupture, drops of both the external liquid and lubricant are present in the cavity leading to a chaotic interaction between the two fluids and finally resulting in random orientation of vectors. On the other hand, a vortex formed at the liquid-lubricant interface signifies a stable LIS with an intact meniscus. The results show that the stability of LIS has a strong dependence on the viscosity of external liquid and the density of lubricant. A more viscous external liquid and a denser lubricant dampen the vibration effects, thereby exhibiting a stable state with an intact meniscus. The amplitude variation ( A = 0.001 - 0.1 m ) surprisingly does not show a significant variation in the failure states. Furthermore, the rate of depletion of lubricant from the cavity and its effect on meniscus failure with time are also illustrated. The results from this work will aid in realizing a robust LIS system with prolonged lubricant retention. © 2024 Author(s).