The Research And Design Of Electromechanical System For Magnetic Immunoassay

Based on the relationship between the magnetic resonance response of magnetic nanoparticles,a kind of magnetic immunometric system was designed to achieve the measurement of the magnetization of magnetic nanoparticles with different hydraulic velocities and to achieve the purpose of biological immunization.Starting from the excitation magnet system,excitation circuit,measurement circuit and sample transmission device,the electromechanical part of the measurement system was simulated,designed and tested.The system was control within LabVIEW environment.Firstly,this paper expounds the biological significance and internal and external development status of magnetic immunization.Combined with the relaxation mechanism of magnetic nanoparticles,the realization principle of magnetic immunization system based on magnetic relaxation theory is expounded.The AC expression of the magnetization response intensity of the magnetic nanoparticles in the liquid phase is deduced.Secondly,in the excitation magnet section,an electromagnet with an air gap is designed to generate an alternating excitation field according to the excitation requirements of the system.Based on Ansys Maxwell simulation platform,the magnetic field distribution of air gap electromagnet with different length air gaps and shapes is simulated,and the hysteresis and eddy current of the excitation device with designing parameters are analyzed.The results show that the design of the air gap electromagnet is reasonable and feasibility.In the excitation circuit part,the peripheral circuit of the driving electromagnet is designed,and the filtering and power amplifier circuit parts are simulated and analyzed.In order to ensure the stable generation of the excitation magnetic field,the PID control program is designed to realize the dynamic control of the excitation current.Designing a three-dimensional mobile platform provides a good basis for stable measurement of the magnetic field distribution of air gap electromagnets.In the measurement loop and sample transmission section,a differential TMR sensor is designed to measure the measurement structure and a compensation coil is introduced to reduce the effect of the background magnetic field on the measurement.According to the experimental requirements,two types of sample carrier mechanisms are designed using stepping motors to achieve precise control of the sample cells.Finally,the linear sample transmission mechanism is used to measure and locate the optimal measurement area of the sensor.The measurement results show that the sensor has the best response position to the magnetic signal in the range of the magnetic field uniform region;the disc sample transmission is installed according to the position information.The mechanism and measurement of different sample concentration response signals show that the platform has a magnetic response resolution of 2.09×10^-4Oe excited by 36 Oe;the solution within 10 nm and 630 nm magnetic nanoparticle particle size is used to experiment under the frequency between 10Hz and 10 kHz.The results show that the magnetization response intensity of particles with larger diameter decays faster,which verifies the feasibility of magnetic immunoassay.