Study On The Flow Characteristics Of Liquid In Micro Inertial Switch

Based on the problems of liquid selection,the poor anti-interference ability,less research of high threshold and flow characteristics of liquid,from the perspective of flow characteristic,the main researches in this paper include flow resistance characteristics of liquid in microchannels,breakthrough pressure and process of passive valve,transient flow model with the influence of surface tension,the suitable of using galium-indium metal and magnetorheological liquid as the moving electrode in the inertial switch.Overall,the purpose of this paper is to provide theoretical reference and extend the application range of micro fluid inertial switch to some degree.1)First,we introduce a method for calculating the pressure drop in a constant cross section microchannel based on the feature size(?),so the fRe in different cross section is carried out.By compared with the existing research results,the rationality of theoretical calculation is verified.Then,for the problem of pressure drop in slowly-varying rectangular cross-section microchannel,the pressure drop prediction model is got by using the fanning resistance formula from constant cross section rectangular microchannels.The CFD simulation shows that the theoretical and simulation results are in good agreement when the contraction angle is less than 12°.2)In order to solve problem of the disunity of passive valve breakthrough process,based on the interfacial energy equation,the fundamentals of hydrophilic capillary valve in a rectangular microchannel is analysed.According to the different central angle on the bending surface,the three-dimensional(3D)theory on the burst pressure is carried out.Experimental apparatus is developed for visualization and measurements of the liquid flow in the microfluidic chip equipped with a capillary valve.Results show that the measurements of burst pressure for the capillary valves are in good agreement with the predictions by the 3D theory model,and the three stages can describe the process of breaking through the passive valve more reasonably.3)Based on centrifugal force,we put forward to a new transient flow model using the N-S equation.Then,the velocity profile,flow rate and the moving front displacement and the pressure distribution along the microchannel are characterized by simplifying the surface pressure.Experiments and CFD simulation are carried out to measure the shift of the flow in rectangular microchannels.According to the experimental data,the flow behavior is affected by the initial pressure and surface tension especially for the case of small microchannel.Moreover,under the same rotation speed,the section size is larger,the Coriolis force is more obvious,which makes one dimensional flow develop into three dimensional flow.Overall,the model can be more reasonable to predict the flow displacement with time.4)An automatic-recovery inertial switch is presented which first adopts gallium-indium(EGaIn)as the switching metal droplet.And the threshold,response time and contact time are measured by employing a small Machete hammer system.By testing the switch in different sizes,we get the influence of micro channel width and electrode position on the switching threshold.The results show that the surface treatment inside the micro channel can solve the problem of the residual effectively,and the switch has the characteristics of fast connection and automatic-recovery.5)Finally,we put forward the design method of the high g value inertial device using intelligent material of magnetorheological fluid.Through the analyses of rheological property of magnetorheological fluid,the threshold formula of magnetorheological valve and flow velocity distribution are established.The numerical analysis results show that the thickness of the center will decrease with the increase of inertia force and inertia force,and the inertia force is the threshold when the center layer thickness value is h.