Design And Optimization Of Microfluidic Chip Directional Flow Wedge Groove Structure

Microfluidic chip technology which widely used in chemical,biological,and medical fields has great development prospects for nucleic acid detection,biochemical analysis,point-of-care testing(POCT),bionic tissues or organs,etc.It has the advantages of miniaturization,automation,integration,and portability.Testing requires only a small number of samples and results can be obtained in a short time.Microfluidic chips which rely on large and complex mechanical devices for sample driving have limitations of application in medical fields such as POCT.However,passive microfluidic chips with microstructured arrays can deliver samples mix thoroughly in microchannels under a low pressure or capillary action,which reduces the reliance on extra mechanical devices and has the advantage of easy operation to prevent backflow.In this paper,a groove structure with wedge-angle microarray(GSWAM)to control the directional flow of microfluidics was proposed.The method of oil film wetting was used to reduce the contact angle and flow resistance of fluid on the surface of PDMS chip.The force analysis for microfluid in GSWAM was carried out through the surface wetting theory combining the GSWAM model.Eventually,experiments were carried out to demonstrate the feasibility of directional flow in GSWAM,providing new ideas for microfluidic devices to achieve the directional microflow.The main contents are as follows.1.A microfluidic control method using a groove structure with wedge-angle microarray was proposed.In the groove structure,the fluid is subjected to different forces in different directions,resulting in directional flow of the microfluid.The flow resistance is further reduced through oil film wetting to enhance the mobility of microfluid.The fluid dynamics analysis of the microstructured recess under capillary action and dynamic pressure difference was carried out.The influences of structural parameters on the performances of directional flow,including tilt angle?,spacing d₂,width w₂and height h₁of the recess.2.Model of microfluidic chip with GSWAM was designed.According to the simulation model of multiphase flow,COMSOL software was used to numerically simulate the flow field of microfluidic chip through fluid-structure coupling.The effect of different microstructures on the channel surface with a contact angle of 60°on the fluid flow was simulated.By comparing simulation results among wedge-angle groove microchannels with different inclination angles,it is found that the microstructure with wedge-angle has a directional diversion effect on the fluid.3.Combined with flow experiments and analysis of chip-related applications.3D printing technology FDM and molding method were used to rapidly fabricate PDMS microfluidic chips with GSWAM.The channel surface was wetted with oil film,then experiments of microfluid in the channel were combined to analyze the directional-flow performance differences among different microstructured chips and optimize the structural parameters;The 30°wedge angle,0.6 mm groove width,0.8 mm depth and 1.0 mm height of the wedge angle groove structure has a good directional drainage effect on the fluid.Experimental results show that oil film wetting can reduce the flow resistance of the PDMS channel and improves the mobility.In addition,the microstructure with wedge-angle can achieve long distance and has a directional diversion effect on the fluid,which realizes the control of microfluid and overcome the gravity for fluid transportation under a certain slope.