Electrohydrodynamic Instabilities in Thin Liquid Trilayer Films PDF Download
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Languages : en
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Experiments by Dickey and Leach show that novel pillar shapes can be generated from electrohydrodynamic instabilities at the interfaces of thin polymer/polymer/air trilayer films. In this paper, we use linear stability analysis to investigate the effect of free charge and ac electric fields on the stability of trilayer systems. Our work is also motivated by our recent theoretical study which demonstrates how ac electric fields can be used to increase control over the pillar formation process in thin liquid bilayer films. For perfect dielectric films, the effect of an AC electric field can be understood by considering an equivalent DC field. Leaky dielectric films yield pillar configurations that are drastically different from perfect dielectric films, and AC fields can be used to control the location of free charge within the trilayer system. This can alter the pillar instability modes and generate smaller diameter pillars when conductivities are mismatched. The results presented here may be of interest for the creation of complex topographical patterns on polymer coatings and in microelectronics.
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Languages : en
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Book Description
Experiments by Dickey and Leach show that novel pillar shapes can be generated from electrohydrodynamic instabilities at the interfaces of thin polymer/polymer/air trilayer films. In this paper, we use linear stability analysis to investigate the effect of free charge and ac electric fields on the stability of trilayer systems. Our work is also motivated by our recent theoretical study which demonstrates how ac electric fields can be used to increase control over the pillar formation process in thin liquid bilayer films. For perfect dielectric films, the effect of an AC electric field can be understood by considering an equivalent DC field. Leaky dielectric films yield pillar configurations that are drastically different from perfect dielectric films, and AC fields can be used to control the location of free charge within the trilayer system. This can alter the pillar instability modes and generate smaller diameter pillars when conductivities are mismatched. The results presented here may be of interest for the creation of complex topographical patterns on polymer coatings and in microelectronics.
Author: Hadi Nazaripoor
Publisher:
ISBN:
Category : Technology
Languages : en
Pages :
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Book Description
The electrified pressure-driven instability of thin liquid films, also called electrohydrodynamic (EHD) lithography, is a pattern transfer method, which has gained much attention due to its ability in the fast and inexpensive creation of novel micro- and nano-sized features. In this chapter, the mathematical model describing the dynamics and spatiotemporal evolution of thin liquid film is presented. The governing hydrodynamic equations, intermolecular interactions, and electrostatic force applied to the film interface and assumptions used to derive the thin film equation are discussed. The electrostatic conjoining/disjoining pressure is derived based on the long-wave limit approximation since the film thickness is much smaller than the characteristic wavelength for the growth of instabilities. An electrostatic model, called an ionic liquid (IL) model, is developed which considers a finite diffuse electric layer with a comparable thickness to the film. This model overcomes the lack of assuming very large and small electrical diffuse layer, as essential elements in the perfect dielectric (PD) and the leaky dielectric (LD) models, respectively. The ion distribution within the IL film is considered using the Poisson-Nernst-Planck (PNP) model. The resulting patterns formed on the film for three cases of PD-PD, PD-IL, and IL-PD double layer system are presented and compared.
Author: Scott Alan Roberts
Publisher: Scott Alan Roberts
ISBN: 1109558511
Category :
Languages : en
Pages : 182
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Author: Ralf Blossey
Publisher: Springer Science & Business Media
ISBN: 9400744552
Category : Science
Languages : en
Pages : 158
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Book Description
This book is a treatise on the thermodynamic and dynamic properties of thin liquid films at solid surfaces and, in particular, their rupture instabilities. For the quantitative study of these phenomena, polymer thin films (sometimes referred to as “ultrathin”) have proven to be an invaluable experimental model system. What is it that makes thin film instabilities special and interesting? First, thin polymeric films have an important range of applications. An understanding of their instabilities is therefore of practical relevance for the design of such films. The first chapter of the book intends to give a snapshot of current applications, and an outlook on promising future ones. Second, thin liquid films are an interdisciplinary research topic, which leads to a fairly heterogeneous community working on the topic. It justifies attempting to write a text which gives a coherent presentation of the field which researchers across their specialized communities might be interested in. Finally, thin liquid films are an interesting laboratory for a theorist to confront a well-established theory, hydrodynamics, with its limits. Thin films are therefore a field in which a highly fruitful exchange and collaboration exists between experimentalists and theorists. The book stretches from the more concrete to more abstract levels of study: we roughly progress from applications via theory and experiment to rigorous mathematical theory. For an experimental scientist, the book should serve as a reference and guide to what is the current consensus of the theoretical underpinnings of the field of thin film dynamics. Controversial problems on which such a consensus has not yet been reached are clearly indicated in the text, as well as discussed in a final chapter. From a theoretical point of view, the field of dewetting has mainly been treated in a mathematically ‘light’ yet elegant fashion, often making use of scaling arguments. For the untrained researcher, this approach is not always easy to follow. The present book attempts to bridge between the ‘light’ and the ‘rigorous’, always with the ambition to enhance insight and understanding - and to not let go the elegance of the theory.
Author: Yoav Tsori
Publisher: World Scientific
ISBN: 9814271691
Category : Science
Languages : en
Pages : 294
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Book Description
This unique book aims to expose the reader to a wide range of phenomena occurring when soft matter systems are put under the influence of an external electric field. The book shows how an electric field can be used to affect objects at the submicron scale, and how it controls the phase behavior of liquids and polymers. The main focus is on the basic underlying mechanisms. Some technological applications are dealt with as well. Book chapters are arranged in a logical order, from OC simpleOCO systems to more complicated ones. In addition, each topic is covered by the mixed bag of theory, experiment and simulation; and this will give the reader a broad perspective of the underlying physical phenomena."
Author: Yoav Tsori
Publisher: World Scientific
ISBN: 9814468142
Category : Science
Languages : en
Pages : 294
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Book Description
This unique book aims to expose the reader to a wide range of phenomena occurring when soft matter systems are put under the influence of an external electric field. The book shows how an electric field can be used to affect objects at the submicron scale, and how it controls the phase behavior of liquids and polymers. The main focus is on the basic underlying mechanisms. Some technological applications are dealt with as well.Book chapters are arranged in a logical order, from “simple” systems to more complicated ones. In addition, each topic is covered by the mixed bag of theory, experiment and simulation; and this will give the reader a broad perspective of the underlying physical phenomena.
Author: Vineeth Chandran Suja
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Liquid films having dimensions that are relatively small in the direction normal to their surface are commonly referred to as thin liquid films. Due to their prevalence in nature and due to their unique geometrical characteristics, a comprehensive understanding of thin film dynamics including instabilities and break-up within thin liquid films is of fundamental and practical interest. Practically this understanding is crucial to tuning the stability thin films in a number of important applications such as for stabilizing foams in foods and beverages, destabilizing foams in lubricants, avoiding surface irregularities in liquid coatings and treating ophthalmic disorders originating from the unnatural breakup of the tear film. Fundamentally, the microscopic thickness of these liquid films along with their large surface to volume ratio presents a convenient framework to investigate characteristics of two dimensional flows, and probe the effects of surface phenomenon such as evaporation and surfactant dynamics on fluid flows. Motivated by the importance of thin liquid films, in this thesis, we experimentally investigate the instabilities and break-up within thin liquid films. In the first part of the thesis (Chapters 2 - 4), we develop and optimize experimental tools and protocols for systematically studying thin liquid films. Notably, we show that single bubble/drop experiments are a convenient and complementary technique to study the dynamics of thin liquid films. Subsequently, we detail a new technique for automatically and robustly measuring the spatiotemporal thickness of thin liquid films - hyperspectral interferometry coupled with machine learning. Finally, we will also establish the operating regimes within which the size of bubbles formed on capillaries for single bubble experiments can be precisely controlled to avoid an air compressibility driven shape instabilities. In the subsequent parts of the thesis we utilize the developed tools to study four different problems - Bubble stability in worm like micellar (WLM) polymer solutions (Chapter 5), Lubricant foaming (Chapters 6 - 8), Drying of thin polymer films (Chapter 9) and Dewetting of the tear film (Chapter 10). In Chapter 5, we explore a problem relevant for the cosmetic industry, and characterize the drainage characteristics of thin films between bubbles and flat wormlike micellar solution - air interfaces. The supramolecular structure and elasticity of the wormlike micelles alters the dynamics of film drainage in WLM as compared to those in thin films containing pure surfactants. The unique features of film drainage include film elasticity driven 'dimple recoil' and a single step transition to a Newton black film beyond a critical film thickness. In Chapters 6 - 8, we explore a problem relevant for the lubricant industry, and study the stability of thin liquid films in lubricants with and without antifoams. Utilizing single bubble experiments, we reveal that the stability of thin films between bubbles in lubricant base oils are enhanced by Marangoni flows driven by the differential evaporation of the various components in the oil. Fundamentally, we also show that the spatiotemporal characteristics of these Marangoni flows are regulated by the concentration and volatility of the volatile species in the oil. Interestingly when the concentration of the volatile species approaches 50%, evaporation driven Marangoni flows become chaotic, with disordered spatial structure, chaotic fluctuations, spatially invariant mean film thickness statistics, high sensitivity to initial conditions, rapidly decaying spatial correlation and a power spectrum for thickness fluctuation that obeys a power law scaling that closely resembles the Kolmogorov's -5/3rd scaling. In the presence of filtered lubricants with antifoams, we reveal that the stability of thin films are positively correlated to the number of filtration cycles, and inversely correlated to the nominal filter pore size and the initial antifoam concentration. In Chapter 9 we explore a problem relevant for film coating, and study the drying of aqueous polymer solutions. Depending on the polymer concentration and the polymer diffusivities, we show that a classical Rayleigh-Taylor instability can develop within the drying solution. We also present the scaling laws describing the onset time of the instability as a function of the physical properties and initial polymer concentrations of the solutions. In Chapter 10 we report a platform to characterize the thickness of the tear film in vivo. By qualitatively comparing the dewetting characteristics observed in vivo with in vitro experiments, we will show that the mechanisms of dewetting is influenced by the presence of interfacial rheology. Further we also reveal that the spatial locations that are prone to dewetting are determined by the presence of interfacial rheology and the spatiotemporal drainage characteristics of the tear film. In Chapter 11 we summarize the findings in this thesis and discuss a number of interesting venues for future research.
Author: Miklós Vécsei
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Chung-Oh Lee
Publisher:
ISBN:
Category : Electrohydrodynamics
Languages : en
Pages : 11
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Author: Raymond John Barlett
Publisher:
ISBN:
Category :
Languages : en
Pages :
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