Research On Properties Of The Antibubble

Antibubble is an uncommon phenomenon whose structure is completely opposite to the soap bubble:in a liquid bath,a water globule is enclosed by an air film.This unique structure implies diverse applications,including microfluidic transportation or drug delivery,ultrasonic imaging,chemical engineering and biomedicine.However,the study of the antibubble is still at the starting stage and research on its formation,lifetime and collapse is lack,especially the lifetime of an antibubble.In general,the lifetime of antibubble is only several minutes or even seconds.This makes it difficult to investigate or utilize the antibubble.The lifetime can be elongated by changing the liquid properties(viscosity and surface modulus),which means additional ingredients and troubles in practice.In this thesis,a systematical and comprehensive study on the antibubbles in the fluid systems is conducted by means of theoretical analysis and high-speed photography.When a droplet impact on a soap film,it leads to various phenomena depending on the impact velocity.The potential mechanism for the collapse of the outer film after the droplet passing through the soap film is presented.Variation of the air film thickness of the antibubble with the impact velocity is studied.When a water drop impacts on a floating oil layer,depending on the impact velocity,different phenomena are observed.In particular,formation of the Water in Oil in Water(W-O-W)particle is analyzed and a theoretical model is built to explain the variation of the particle diameter with the impact velocity.Bouncing antibubbles on the liquid or solid surfaces are studied.Threshold for the bouncing antibubble on the liquid surface is presented.Variation of the dimensionless contact time of the bouncing antibubble on the liquid and solid surfaces with the impact velocity is investigated.Two methods for controlling the lifetime of the antibubble are proposed:vertical vibration and jet flow.Moreover,the corresponding setups are designed and the lifetime is observed to significantly elongated.The outline of this thesis is as follows,In Chapter 1,the background and significance of this thesis are proposed.Literature on the formation,lifetime and collapse of the antibubble are reviewed.The main content of the thesis is summarized.In Chapter 2,different phenomena are presented when a droplet impacts on a soap film,depending on the impact velocity.A regime map is presented to categorize these phenomena.Collapse of the outer film and formation of the antibubble after the droplet passing through the soap film are presented.Meanwhile,antibubbles can be generated when a high-speed droplet straightly impacts on the liquid bath.The potential mechanism and the variations of the antibubble diameter and air film thickness with the impact velocity are studied.In Chapter 3,a regime map of the impact results of a water drop on the floating oil layer is presented.If the impact velocity is high enough,one impact leads to two Water in Oil in Water(W-O-W)particles named as primary and secondary W-O-W particles,respectively.Diameter of the primary particle maintains almost the same,while the satellite particle enlarges with the impact velocity.A theoretical model is built to explain this phenomenon.In Chapter 4,the bouncing antibubbles on the liquid and solid surfaces are presented.For the liquid surface,effect of impact velocity and viscosity on the surface deformation,restitution coefficient and contact time is investigated.Moreover,the threshold for the antibubble bouncing on a liquid surface is presented.For the solid surface,variation of the antibubble deformation and contact time with the impact velocity is analyzed.In Chapter 5,two methods are proposed to control the antibubble lifetime.Effect of the vertical vibration on the lifetime and the corresponding mechanism are studied.A jet generator is designed to investigate the effect of jet flow on the antibubble lifetime.These two rmethods both help to significantly increase the antibubble lifetime.In Chapter 6,the research work of the thesis is summarized with further prospect.