Research On Nucleic Acid Extraction Microfluidic System Driven By Shape Memory Alloy

Real time disease diagnosis technology based on microfluidic technology is gradually becoming one of the most effective and fast ways to control the spread of infectious diseases and diagnose diseases in the field and remote areas.However,because the components of the traditional microfluidic system still use conventional size pneumatic components,the microfluidic system is bulky and complex in structure,and it is difficult to integrate with the microfluidic chip itself into a complete system,which becomes the biggest obstacle for the further high integration of the microfluidic system.In this paper,a microfluidic system for nucleic acid extraction based on shape memory alloy(SMA)is proposed.Its principle is simple,modular and highly integrated.By combining micro devices,microfluidic technology and intelligent control technology,the automation of nucleic acid extraction process is realized.Based on soft etching technology,a PDMS-ITO glass microfluidic chip with integrated heating and temperature measurement functions is proposed for the method of extracting nucleic acid by magnetic beads,using polydimethylsiloxane(PDMS)and indium tin oxide(ITO)conductive glass as raw materials.A modular test kit for extruding PDMS diaphragm driving reagent using shape memory alloy(SMA)as driving element is designed.The dynamic and thermodynamic mathematical models of SMA are established,and the simulation analysis and experimental research are carried out.The influence of SMA spring current on system temperature is analyzed,and the key parameters such as martensite content,driving force and driving displacement are further affected.The steady-state and transient dynamic models of the driving diaphragm are established to explore the force and deformation of the diaphragm under the action of SMA.The parameters are optimized and verified according to the simulation and experimental results.Aiming at the temperature control requirements and automation in nucleic acid extraction,a temperature control system is built.The heating area and temperature sensor are etched on the ITO glass by etching technology.The ITO glass heating substrate and the ITO temperature sensor are respectively arranged on both sides of the chip to realize the functions of heating and temperature measurement.The heat transfer model of microfluidic chip is established,and the steady-state and transient thermodynamic models of the chip are studied.The experimental research of nucleic acid extraction microfluidic system driven by SMA is carried out.The temperature control system is calibrated and tested to verify the temperature control effect.The driving characteristics of SMA spring are tested.The feasibility of nucleic acid extraction process based on microfluidic technology is verified by modular combination of PDMS-ITO glass microfluidic chip,SMA film driving kit,temperature control and logic control system.Using COMSOL simulation software,the fluid flow field simulation of the chip and driving module is built,and the characteristics of the fluid in the driving process are studied.