Study Of Theory And Method For Temperature Probing Using Magnetic Nanoparticles

In recent years, temperature probing for accurate characterization of atomic, molecular and cellular heating transition is an emerging challenging and groundbreaking research topic. This thesis proposes a novel theory and method for temperature probing using magnetic nanoparticles (MNP). This dissertation employs temperature sensing model and its corresponding techniques for precise generation of magnetic field to investigate several approaches and inverse calculation methods by designing a system for magnetic measurement guided by numerical simulation. Finally, theoretical and technical problems are solved to achieve a new approach of precise and noninvasive temperature probing using MNP. The main content is as follows.First of all, by studying the model of susceptibility and temperature of MNP in DC field, this thesis employs numerical solution of nanomagnetic model to propose a novel method for magnetic nanothermometry. On the basis of the Taylor’s expansion of nanomagnetic model, discrete matrix equations constructioin with respect to temperature and susceptibility and inverse calculation method are used for magnetic nanothermometry. Simulation and experimental results from SQUID VSM prove the theoretical and technical viability of magnetic nanothermometry, which allows a temperature probing accuracy of0.57℃. Furthermore, the impact of Taylor’s expansion, inverse calculation method and applied magnetic field upon temperature probing accuracy, as well as its mechanisms, is studied to improve the magnetic nanothermometry, which allows a temperature accuracy of0.02℃.To improve the real-time performance of temperature probing and get rid of the complex system for generating magnetic field using superconducting magnet, this thesis designs a new system for generating triangular-wave magnetic field to achieve the approach of temperature probing using MNP. A field-generating system based on multi-functional data acquisition card (DAQ), linear power amplifier and Helmholtz coil, and a weak magnetic measurement system using detection coil are employed to design a detection system for real-time MNP magnetization curve. In addition to the sensing model for magnetic nanothermometry in triangular-wave magnetic field, temperature is calculated by the physical model of temperature and magnetization curve of magnetic nanoparticles. The protocol allows a temperature accuracy of0.1℃with a real-time performance of1s.Taking into account the demand of temperature imaging, this thesis designs a temperature measurement system using MNP in sinusoidal wave magnetic field. Base on the study of MNP magnetization spectrum, a new model for magnetic nanothermometry using the first and third harmonics of MNP magnetization is constructed. And the solution of the model is achieved by inverse calculation and optimal theory. Finally, a protocol for temperature probing using MNP magnetization spectrum is designed, which allows real-time and precise temperature probing with an accuracy of0.2℃. Furthermore, the dissertation investigates the impact of magnetization harmonic measurement on temperature probing accuracy and proposes to employ the first and second harmonics of MNP magnetization induced in AC and DC magnetic fields to achieve the approach of real-time and precise temperature probing. And experimental results allow a temperature accuracy of0.09℃.At last, to improve magnetic nanothermometry, this thesis has a further investigation on the thermal effect of magnetodynamic behavior of magnetic nanoparticles. Simulation indicates that the influence of clustering behavior of magnetic nanoparticles in magnetic fluids on the parameter of saturation magnetization affects precise magnetic nanothermometry. The size distribution and clusters as well as their thermodynamic behavior are the key factors of magnetic nanothermometry. The investigation provides proof for the selection of best suitable MNP sample for magnetic nanothermometry.