Multiphase Interfacial Phenomena for Liquid Manipulation and Defrosting

Interfacial phenomena are prevalent in various natural and engineered systems. A thorough understanding of these phenomena is essential for a complete understanding of processes such as phase transitions and interaction of liquid droplets with different surfaces. The insights gained from understanding interfacial behavior are pivotal in fields such as pharmaceuticals, microfluidics, material sciences, and environmental engineering. This dissertation aims to advance our understanding of interfacial behaviors, thereby facilitating the development of innovative technologies for applications in health, defrosting, and omniphobic surfaces. In Chapters 1 and 2, relevant background information and goals are provided to contextualize the research being presented in this dissertation.

Chapter 3 introduces a novel metal-free alternative to conventional antiperspirants (containing aluminum salts and zirconium salts). We leverage the composition of human sweat (97% water and 3% minerals) and employ a hygroscopic substance near the outlet of an artificial sweat duct rig. This leads to complete diffusion and dehydration of sweat, forming a natural mineral plug within the artificial sweat duct that halts the flow.

Chapter 4 examines the behavior of room temperature water droplets spreading on a flat icy substrate. The use of flat ice, as opposed to cold substrates, eliminates the nucleation energy barrier, enabling freeze front initiation as soon as the bulk temperature of the spreading drop reaches 0 C. Through scaling analysis, we identify distinct thermo-hydrodynamic regimes with varying Weber numbers.

Chapter 5 presents a novel construct for lubricant-impregnated surfaces (LIS). To date, most of the investigations characterizing the wettability of LIS have focused on droplet mobility. We pioneer a lubricant-impregnated fiber (LIF) which exhibits unique droplet dynamics due to simultaneous exploitation of both, high mobility and high adhesion.

Chapter 6 proposes an innovative approach for defrosting by exploiting the polarizability and natural thermo-voltage of frost sheets. By placing an actively charged electrode near the frost sheet, we observe that frost dendrites migrate towards the electrode. This technique, termed Electrostatic Defrosting (EDF), effectively removes up to 75% of the frost mass for superhydrophobic surfaces and 50% of the frost mass for untreated surfaces in less than 100 s.