Effect of diamagnetic contribution of water on harmonics distribution in a dilute solution of iron oxide nanoparticles measured using high-Tc SQUID magnetometer

The magnetization curve of iron oxide nanoparticles in low-concentration solutions was investigated by a highly sensitive high-Tc superconducting quantum interference device (SQUID) magnetometer. The diamagnetic contribution of water that was used as the carrier liquid was observed in the measured magnetization curves in the high magnetic field region over 100 mT. The effect of the diamagnetic contribution of water on the generation of harmonics during the application of AC and DC magnetic fields was simulated on the basis of measured magnetization curves. Although the diamagnetic effect depends on concentration, a linear relation was observed between the detected harmonics and concentration in the simulated and measured results. The simulation results suggested that improvement could be expected in harmonics generation because of the diamagnetic effect when the iron concentration was lower than 72 μg/ml. The use of second harmonics with an appropriate bias of the DC magnetic field could be utilized for realization of a fast and highly sensitive detection of magnetic nanoparticles in a low-concentration solution

SQUIDs in biomagnetism : A roadmap towards improved healthcare

This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 686865.Peer reviewedPublisher PD

Effect of Core Size Distribution of Immobilized Magnetic Nanoparticles on Harmonic Magnetization

In magnetic particle imaging (MPI), harmonic magnetization signals detected from magnetic nanoparticles (MNPs) are used to image the spatial distribution of the MNPs. The strength of the harmonic signals is directly related to the sensitivity of the MPI system. In this study, we used numerical simulations based on the Fokker-Planck equation to explore the effect of the core size distribution of an immobilized MNP sample on the harmonic signals. We assumed an anisotropy value of 5 kJ/m^3 and a uniform volume-weighted core size distribution of MNPs ranging from 17.4 to 37.6 nm to simulate a typical MNPs sample. First, we show that the strength of the harmonic signals of the MNP sample were much lower than calculated from the scalar summation of the harmonic signals generated from each MNP in the sample. For example, the strength of the 9th harmonic signal decreased to one-third. This indicates that about 67% of the 9th harmonic signals generated from each MNP are mutually cancelled. We then show that the phase lag of the magnetization due to a finite Néel relaxation time caused lower harmonic magnetization signals of the MNP sample when the core size was distributed. These results indicate that an MNP sample with a narrow size distribution and small anisotropy energy would effectively improve the sensitivity of the MPI system

磁気的バイオセンシング

九州大学公開講座 先端サマーセミナー2016 I&Eの未来を創るシステム情報科学 : 2016年8月16