Study On The Motion Characteristics Of Bubbles And Magnetic Liquid Marbles Under Magnetic Field

The phenomenon of magnetic particles directional movement under the effect of magnetic field is magnetophoresis.In the past,only the magnetic particles can be controlled remotely by magnetic force.However,the appearance of magnetic fluids make it possible to manipulate the non-magnetic particles.We often need to manipulate and separate the droplets or non-particles in the micro flow technology,life science and chemical analysis.Magnetic field is an ideal means of the manipulation of particles owing to it doesn't need the direct contract with simples and the simples don't need to be charged or heated.In view of the manipulation of micro quality fluid and non-magnetic practices in the magnetic fluid has important potential application in the micro flow technology,this thesis investigate the movement of bubbles in the magnetic fluid and liquid marble under the effect of magnetic field,aim to find the influence of magnetic field on the magnetic particles and non-magnetic particles in the magnetic fluid and expanding the application of magnetic fluid.Also hope to provide a new method for the directional transportation of micro mass liquid based on the properties of liquid marble.This thesis derived the magnetic force formula of magnetic and non-magnetic objects in the magnetic fluid under the action of magnetic field.An object is subjected to magnetic force only when its magnetization is different from its surrounding medium,and the magnetic force is proportional to the magnetization and gradient of magnetic field.Because of the magnetic force on non-magnetic object in the field is very weak and the magnetic fluid is a black opaque colloidal liquid,the conventional experimental conditions are difficult to observe the movement phenomenon of particles caused by magnetic field.This thesis choose the bubble in the gap vessel as the research object,using the characteristics of bubble such as small quality,easily to be drove and observed to investigate the influence of magnetic field on non-magnetic object in the magnetic fluid.The predicting formula of bubble velocity is deduced by introducing the influence of magnetic force on the basis of the classical theory of bubbles in the narrow gap filled with ordinary liquid and verified by experimental data.It is found that the direction of magnetic force on the non-magnetic object in the magnetic fluid is in the direction of decreasing the intensity of magnetic field.In contrast with bubbles which are the non-magnetic objects in the magnetic fluid,the surrounding medium such as air or liquid around magnetic fluid marbles have no magnetism,the direction of magnetic force on the magnetic fluid marble is opposite to the bubble,which is in the direction of increasing the intensity of magnetic field.The thesis presented using the magnetic field to control the marble floating on the liquid surface to realize the directional conveying of micro mass liquid on the other liquid surface.Because of the exist of hydrophobic of the power particles on the marble surface and the effect of surface tension,liquid marbles can float on the liquid surface even they are denser than the carrier fluids.This thesis assumed the part of the marble immersed in the carrier liquid as a bass segment,and the static equilibrium equation of a marble on the liquid was established.The figures of marbles with different volumes were observed and recorded by micro distance photography,and the static equilibrium equation of floating marbles has been verified.It is different from an ordinary object floating on the liquid which is the balance of gravity and buoyancy,the gravity of a floating marble is balanced by the buoyancy and the surface tension,and the surface tension plays a major role which make the marble can float on the liquid even its density is larger than the carrier liquid.In this thesis,the magnetic force,viscous resistance and the resistance caused by contact angle variety of floating marble which is subjected to a non-uniform magnetic field have been analyzed respectively,and the quantitative relationship between marble velocity and the parameters of magnetic and flow field was obtained.We prepared magnetic fluid marbles with different volumes,and the velocities of magnetic fluid marbles with different volumes under the different intensity and gradient magnetic field were measured.The velocities of experiment measurement and theoretical calculation were analyzed comparatively.Based on theoretical and experimental research,we tried using the magnetophoresis force to manipulate the floating marble to conduct "table tennis" and "bypassing obstacle" experilents,which also demonstrates that the magnetism canoffers a promising non-contact control approach to manipulate small quantities of liquids.It is hope that this thesis can provide the theoretical and experimental basis for the directional transportation of micro mass liquid on the liquid surface,and explain the magnetophoresis effect of magnetic field on the magnetic particles.