Research On Key Technologies Of Magnetic Nanoparticles Thermometer

Comparing with traditional thermometers,magnetic nanoparticles thermometer uses the magnetization of magnetic nanoparticles(MNPs)to construct a magnetic-temperature model,which can accurately measure temperature in living bodies and opaque objects in real time.It has obvious advantages in biomedicine(tumor hyperthermia,targeted drug delivery,etc.)and industrial applications(IGBT,high-power LED,etc.),but there are still some problems in practical applications.Firstly,this thesis study the magnetic-temperature basic model based on Langevin function while ignoring the relaxation effects under the low-frequency excitation magnetic field.However,the magnetization of MNPs is indeed affected by rotational relaxation effects(including Brownian relaxation and Néel relaxation).(1)A harmonic measurement model of MNPs dominated by Brownian relaxation is proposed,which is based on the difference of AC magnetization described by Langevin function and Fokker-Planck equation.The simulation and experimental results show that the harmonic model can accurately describe AC magnetization response;(2)When Néel relaxation is dominant,we proposed a magnetic-temperature model constructed under a high-frequency excitation magnetic field.The experimental results show that the empirical harmonic compensation model can accurately describe the AC magnetization.The measured maximum temperature error is less than 0.008 K in the temperature range of 310-320 K.It is also expected to improve the application range of MPI and MNPT.Secondly,the digital phase-sensitive detection(DPSD)algorithm is introduced,which is used in MNPs thermometer.The anti-noise performance of the DPSD algorithmm is analyzed from the perspective of Gaussian noise,industrial frequency magnetic noise,and higher frequency magnetic noise and compared with the fast Fourier transform(FFT)algorithm.It is found that the solution accuracy of DPSD algorithm is higher than that of FFT algorithm when the signal-to-noise ratio is low,and it is easy to adjust parameters of DPSD algorithm.Finally,the MNPs thermometer was successfully applied to the component integration in the industry.We explored the method of evaluating the IGBT thermal network parameters based on the magnetic nanothermometer,and introduced the experimental system’s device and experimental process.The experiment verifies that the IGBT thermal network parameter evaluation method based on MNPs thermometer is feasible.It is a new direction for the application of MNPs thermometer.