Research On Double-dilution Microfluidic Chip Based On Microchannel Structure

In antimicrobial susceptibility test,a series of double-dilution of the antibacterial drug were usually performed by manual operation to determine the minimum inhibitory concentration(MIC)of the drug for a particular fungus.Manual operation is not only complicated,but also introduces errors,resulting in inaccurate experimental results.How to achieve the double-dilution of reagent samples quickly,conveniently,and accurately is the key to solve this problem.In recent years,with the rapid development of micro-total analysis system(?-TAS),concentration gradient microfluidic chip as a new type of device,with its small size,fast response and high integration,have a wide range of applications in biochemical analysis,chemical synthesis,clinical testing and many other fields.Based on the theory of microfluidic gradient network,a microfluidic chip with multi-stage double-dilution function of liquid for a specific concentration was designed and prepared.In this paper,the fluid flow state and the mass transfer law between fluids inside the microfluidic chips driven by pressure are analyzed theoretically.In order to investigate the factors affecting the mixing efficiency between fluids under laminar flow conditions,a T-type square-wave channel micromixer with baffle structure was designed.The simulation results are compared with T-type straight channel micromixer and T-type square-wave channel micromixer.The results show that the change of microchannel structure affects the flow state of the fluid,shortens the diffusion distance between fluids,and accelerates the mixing between fluids.Under the guidance of theoretical analysis and simulation results,this paper designs a microfluidic chip with double-dilution function by equivalent circuit analogy method.The microchannel network is equivalent to the circuit.The length of the microchannel is calculated and optimized by Kirchhoff's law.The influence of different inlet flow rate on the concentration gradient was studied by COMSOL simulation software.Finally,the optimal setting of inlet flow rate is determined.In this paper,polydimethylsiloxane(PDMS)was used as material to prepare the chip by combining the micro-fabrication technique.This includes the fabrication of the Si mold by photolithography,the PDMS substrate is obtained by molding,and finally the bonding of the PDMS substrate to the glass is achieved by oxygen plasma.After the establishment of the microfluidic experimental platform,the doubledilution function of the microfluidic chip was determined qualitatively and quantitatively by using pigment and sodium fluorescein reagent,respectively.The experimental results show that the chip reaches the expected requirements.When the volume flow rates of the two chip inlets are set to 1.225?L/min and 0.375?L/min respectively,the twice diluted reagent sample can be obtained at the four outlets of the chip after 4 min,and the dilution precision reaches 98%.The concentration state can be kept stable for a long time.The research of the chip proposes a new method for the dilution of antibacterial drugs,and it has important application value in the research and evaluation of new drugs.