Design Of Weak Magnetic Field Measurement System For Magnetic Nanoparticles

The thesis aims to design a weak magnetic field measurement system employingmagnetoresistive sensor HMC1022in order to measure magnetic nanoparticles’magnetization or magnetic susceptibility so that some magnetic characteristics such asthermal dynamic behaviors can be investigated. And the homemade measurement system hasa great significance in the development of magnetic nanoparticles in biomedical applicationssuch as MR contrast agents, cancer hyperthermia and nanoparticle temperature estimation.Firstly, employing the research and analysis on weak magnetic field measurementsystem, in addition to summarizing the sensor characteristics of weak magnetic fieldmeasurement such as performance parameters, manufacturing design and production cost,the thesis takes into account the requirements of weak magnetic field measurement uponmagnetic nanoparticle. At last, the magnetoresistive sensor HMC1022is selected to measurethe magnetization of magnetic nanoparticles. Secondly, hased on the characteristicsparameters of magnetoresistive sensor HMC1022, the zener diode TL431and MOS FETIRF7105are used to design the drive and set/reset electronic circuits, respectively. Then theoutput signal from sensor HMC1022is amplified by the instrumentation amplifier AD620.At last, the single-end signal is transformed to differential signal, which will be inputted intothe Data Acquisition Card. At last, using the data acquisition card produced and theLabVIEW software development platform, the thesis designs a software system with dataacquisition, data processing such as digital phase sensitive detection algorithm and datapreservation in order that it can acquire the real-time magnetization amplitude of magneticnanoparticles, and achieve a real-time display of the magnetic nanoparticles’ temperatureversus inverse susceptibility curve, eventually save the experimental data.The homemade system is used as a platform for the experiments of magnetic fluid sample. And the experimental curve of temperature versus inverse susceptibility data is fittedby modified Langevin function in MATLAB. And the experimental data coincide withtheoretical model well. It indicates that the homemade system succeeds in the investigationof thermal dynamic behaviors of magnetic nanoparticles.