Basic Research On Inductive Magnetic Nanoparticles Detection

The magnetic induction testing technology mostly uses eddy current testing principle to imaging the electrical conductivity distribution of the tested objects.It determines the conductivity distribution information of the detected objects in the detection area according to the phase difference of the detected signal.The magnetic induction testing technology extracts the useful signals from the detection coil,which is the key factor for determining the imaging quality.Because the magnetic induction detection technology has a strong dependence on the conductivity of the measured object,the eddy current induced by the magnetic field passing through the human tissue with small conductivity is weak,which leads to the phase difference between the induction signal and the original signal in the detection coil is not obvious.In addition,the induced signal and the original signal are at the same frequency,which increases the difficulty of extracting the phase difference of the signal.Magnetic induction detection technology is also very sensitive to the magnetic permeability of the measured object.This article proposes a magnetic induction detection method based on magnetic permeability based on the magnetic permeability detection principle of magnetic induction detection technology,combined with medical magnetic materials-magnetic nanoparticles.According to the superparamagnetic and nonlinear magnetization characteristics of magnetic nanoparticles,the third harmonic amplitude of the signal spectrum in the detection signal is used as the detection target,and the detection signal is distinguished in frequency from the original signal.Relative to eddy current detection,the signal phase is the target,To establish a new detection method.This paper studies the principle of magnetic induction detection technology and the physical properties of magnetic nanoparticles.Firstly,the magnetization response of magnetic nanoparticles in a sinusoidal magnetic field is modeled,the AC magnetization model of Langevin function is analyzed,and the polynomial detection model is expanded by Taylor.Secondly,using the phenomenon of repeated magnetization saturation of the particle model in the AC magnetic field,the induced voltage signal obtained is different from the voltage signal of the excitation magnetic field,and the detection system is designed by detecting the third harmonic of the signal,including the solenoid coil to generate a sector-shaped excitation magnetic field.The detection coil and the differential coil form a differential detection system.Then a simulation experiment is carried out on the designed detection system to study the factors affecting the third harmonic of the signal.Finally,the influence of excitation magnetic field,particle number and particle position on the third harmonic signal is verified by the experiment of inductive detection system.The results show that the method of induction magnetic nanoparticles detection is feasible.