| In recent years,with the rapid development of science and technology,microfluidics is widely used in the fields of biology,medicine and chemistry.As an important part of microfluidic technology,microfluidic driving is a precise pumping technology that achieves microliters or even nanoliter of fluids through various driving methods,including hydrodynamics,materials science,biology,mechanics and electromagnetics,etc.Micropump is a common device to realize micro-fluid driving.It has made great research progress and has shown important and extensive application prospects in life science,biomedicine,aerospace and other fields in these years.This paper based on the dynamic driving method of micro-magnetic fluid,a magnetic fluid micro-pump has been developed and the effective pumping of micro-fluids has been realized.Firstly,in order to better select the structure of the pumping chamber and the way of magnetic fluid drive,the finite element method of ANSYS simulation software is used to simulate the specific structure of the chamber and the mode of magnetohydrodynamic motion.The annular chamber is selected as the channel structure of the pump chamber,the inlet and outlet passages of the pump chamber are at an angle of 60 degrees apart from each other;The magnetic fluid is arranged in two parts in the pump chamber,one part is fixed in the annular passage between the inlet and outlet,the other part is driven by the external force to do circular movement along the annular passage.Secondly,the specific fabrication of the driving chamber is studied.Polymethyl methacrylate(PMMA)is selected as the pump chamber material in the experiment.In order to solve the problem of magnetofluid contamination of the pumped liquid,silicone rubber is used as the pump chamber diaphragm in the experiment to separate the magnetofluid from the pumped liquid.In order to complete the pump cavity bonding effectively,the bonding conditions of the existing PMMA are improved in this paper.And the orthogonal test design is used to analyze,design and test the bonding temperature,time and pre-pressure parameters affecting PMMA bonding results.The optimal bonding condition is: bonding temperature 115 ° C,time 70 min,pre-pressure 60 N.The pump cavity substrate is fabricated by laser engraving,and the pump cavity is effectively bonded and packaged according to the improved bonding conditions.Thirdly,an external magnetic field control unit is designed to drive the magnetic fluid motion.The unit uses a single-chip computer setting program to send driving signals to L298 N for amplification,then its signal drives the stepping motor to rotate in accordance with the specified speed and direction,and drive the permanent magnet on the rotor to move,the rotor drives the magnetofluid displacement,causing the deformation of the pump chamber diaphragm,and then drives the pumped liquid to move to complete the pumping function of the magnetofluid micro pump.The control unit can control the rotation speed and direction of the motor through the buttons in the circuit,and display the rotation speed and rotation angle through the display.Finally,the pump chamber and the external magnetic field control unit are integrated and encapsulated to start the test experiment of micro-pump pumping.In this paper,the performance of the micropump is verified and tested by measuring the pumping flow rate and pumping back pressure of the micropump.The maximum flow rate of the micropump is 156.8?L/min and the maximum back pressure is 666.4Pa.The experimental results reached the expected indicators and met the application requirements. |
PDF Full Text Request