The Fluidic Dynamics And Applications Of Rotational Flow Based On Electrohydrodynamics Force In A Microchamber

With the new MEMS technology and micromachining technology increasingly being used in integrated microfluidic device to generate and analyze biological samples and automated compound,the sample needs to be quickly and efficiently mixed.However,most existing microfluidic mixing devices are primarily mixed by diffusion.So it is necessary to find a fast and efficient hybrid method.Electrohydrodynamics(EHD)is an interdiscipline which combines fluid mechanics and electrodynamics.Currently,EHD force is usually utilized to control and manipulate the liquid in the confined system due to the advantages of the ease of its applicability on the micro scale.The electro-rotation phenomenon produced by EHD is widely used in biological and microfluidic chips.Faetti et al.and Morris et al.demonstrated that the vortices were generated in the freely suspended liquid crystal films when applying an electric current through it.Recently,the rotating flow produced by EHD force in freely suspended liquid film has been reported by Amjadi et al.and Shirsavar et al.In the previous studies,they all investigated the rotation of a thin suspended film.However,the thin film liquid is very easy to break and hard to stand for a long time,the current experiments cannot provide a practical way in microfluidic devices.In this article,we present an idea of a microfluidic chip in which the electro-rotation phenomenon is used.Therefore,an electro-rotation device based on the principle of electroosmotic flow is proposed.The mechanism is particularly attractive due to the ease of its applicability on the micro scale and its success in achieving control of the bulk liquid in a confined domain.This new method eliminates the need for external electrode plates and the requirement of any moving part.This paper mainly proposes two simulation models.The first model is a model in which the electrodes are placed on the side wall of the microchamber.By using COMSOL software to simulate,the numerical results of flow field and motion of microparticles under applied voltages are obtained,and the simulation results are analyzed.The second model a model in which the electrodes are placed on the bottom of the microchamber.Considering in practice,the size of the first model that can be obtained under the existing conditions is about 1 mm.If it was at the nanometer level,it will be difficult in practical operation,so it is considered that we place the electrode on the bottom of the microchamber is a better method.Finally,the simulation results are obtained through COMSOL for analysis.Based on the above two models,it is improved to establish a suitable micro-mixing model.Different micro-mixing models are proposed,and the simulation results are quantitatively compared through numerical simulation experiments and mixing coefficients.Finally,this paper provides an experimental method based on the model in which the electrodes are placed on the side wall of the microchamber.Through experimental research,the rotation of the electroosmotic flow drive in the microchamber is verified.The numerical simulation results demonstrate the excellent mixing effect of the proposed method and provide a viable way to realize the mixing in microfluidic devices.