| Popis: |
Measurement system using cooled pickup coil and superconducting quantum interference device (SQUID) picovoltmeter was developed to detect magnetic nanoparticles for bio-sensing application. The susceptibility measurement method using an excitation field was used to detect the magnetic nanoparticles. We first showed a method to cancel noise from direct flux-linkage of excitation field in order to measure weak signal field in the presence of large excitation field. Next, we clarified the properties of the magnetic filed generated from the particles, such as lift-off dependence and the spatial variation of the signal field. Good agreement was obtained between experiment and analysis. Analyzing the contour map of the signal field, we could identify the three dimensional position of the particles. At present, we could detect Fe_3O_4 particles with weight of 200μg at the lift-off of 30mm. Methods to further improve the system performance were also discussed. |
