| The spring up of microfluidic technology has been widely concerned by researchers in the fields of chemistry,biology,electronics and machinery and so on.The flow of fluid in the internal channels of the microfluidic chip leads to many different characteristics from the macroscopic system due to the microscale effect.At the same time,it has also promoted the production of many different membrane-free extraction and separation technologies and the further development of the sample preparation technology.The research object is the liquid-liquid extraction of the microfluidic chip in this paper.The theoretical basis,working principle,structural parameters and the influence of working parameters are analyzed.The theoretical method and research experience of liquid-liquid laminar flow extraction are enriched.The main content of this work is as follow:Firstly,the theoretical basis of laminar liquid-liquid extraction and extraction technology is introduced.Introduced different structures and methods for extraction and the basic principle of multiphase laminar flow is established.Due to the difference in concentration gradient between the organic phase and the aqueous phase,the metal ions are mass-transferred from one of the higher concentrations in one direction,and the microchannel is divided into the preparation stage,the mixing stage,and the separation stage,were came up with the first time.By adding the auxiliary structure in the mixing stage,the degree of turbulence of the fluid is enhanced,and the contact area of the two phases is increased,so the liquid-liquid extraction efficiency is increased.Secondly,the influence of the roughness of the inner wall surface on the fluid flow is analyzed.Based on the Derjaguin approximation,surface energy,and Casimir effect,influence rules of surface roughness on flow characteristics and continuous directional transport efficiency and constitutive equations and flow control equations for fluids are defined in the micro-channel are revealed by both computational and experimental methods.All the above results are verified as effective and credible.The results indicate that roughness of the inner wall is a very important factor which can affect both flow characteristics and continuous directional liquid transport efficiency in the micro-channel.Whether equivalent tooth number,tooth height or dip angle of the tooth,their variation all can bring a prominent change of main vortex and concomitant vortex in clearance flow near inner wall,which will cause the continuous directional transport efficiency of immense microfluidic changes.Thirdly,the effects of different auxiliary structures and inlet structures on liquid-liquid extraction in microchannel were analyzed.The extraction effect of the cross-type auxiliary structure is unstable.The cylindrical auxiliary structure can effectively improve the extraction efficiency of the microfluidic liquid-liquid extraction.Therefore,adding a suitable auxiliary structure can improve the extraction efficiency.The inlet flow velocity or the two-phase contact time or the two-phase contact interface on the extraction efficiency were compared.The proportion of the two phases in the width direction of the microchannel has little effect on the extraction efficiency.The extraction efficiency is higher when contact time is 5-10 s.The extraction efficiency increased with the increase of the contact interface.However,the extraction efficiency is not greatly improved with the contact interface continues to increase.Therefore,according to the basic principle of multiphase laminar flow proposed in Chapter two,the contact interface is increased,and the length of the microchannel should be Shorten.Otherwise,it is prone to stripping.Finally,the experimental platform of liquid-liquid extraction of the microfluidic chip was built.The experimental equipment of liquid-liquid extraction experiment,as well as the analytical detection method,were introduced,and the precautions for experiment were put forward. |
PDF Full Text Request