Tip Streaming of Simple and Complex Fluids

This book comprehensively describes the tip streaming in simple fluids and those containing surfactants and polymeric molecules. It summarizes the theoretical models and approximations commonly adopted to analyze this phenomenon. It provides relevant experimental results and presents the scaling laws for rationalizing those results. The stability of the flows leading to tip streaming is analyzed theoretically and experimentally. Attention is paid to the effects of surfactant monolayers and viscoelasticity, including solutocapillarity, interfacial elasticity, surface viscosity, and extensional thickening caused by the polymer coil-stretch transition. It also offers an overall perspective of the numerous technological applications of the tip-streaming phenomenon. Remarkable examples are the production of microemulsions and microencapsulation of active agents for the food and pharmacy industries, the atomization of charged liquids for analytical chemistry, and the ejection of ultra-fast and ultra-thin jets for crystallography. Physical mechanisms responsible for the onset of tip streaming driven by hydrodynamic and electrohydrodynamic forces are described. Relevant theoretical and experimental results of the periodic microdripping and continuous microjetting modes of tip streaming produced with microfluidic configurations such as electrospray, flow focusing, coflowing, and selective withdrawal are discussed. The physical mechanisms responsible for the instability of the microjetting mode are studied in detail. The book collects the scaling laws used to predict the outcome of the microfluidic configurations mentioned above. The author combines state-of-the-art experimental results and linear stability analysis to identify the instability mechanisms limiting the applicability of the above-mentioned microfluidic configurations. In this way, the book connects experimental observations with fundamental aspects of tip streaming, bridging the microfluidic and fluid dynamicist communities. The connection between results obtained from the theoretical and experimental approaches will help experimentalists to understand the fundamental aspects of their practical problems. A useful guide for researchers working on hydrodynamic focusing and electrospray.