励磁音響効果に関する基礎的研究

抄録

The use of magnetic nanoparticles in biomedical applications has been studied for a long time. When magnetic nanoparticles are exposed to a magnetic field they exhibit various responses. We have been focusing on the phenomenon by which magnetic nanoparticles dispersed in a liquid emit sonic waves when they are exposed to an AC magnetic field. We term this phenomenon as sonic wave emission by stimulated magnetic nanoparticles (SWESMAN). SWESMAN is a very recent phenomenon as it was first discovered in 2008. Magnetic nanoparticles exposed to an alternating magnetic field of frequency f emit a sonic wave of frequency 2f. In this paper, we demonstrate that the positions of magnetic particles embedded in a polymer gel can be determined from the acoustic pressure of the sonic waves that they emit, since the acoustic pressure is proportional to the distance between the magnetic particles and the detection point. We also propose other potential applications of SWESMAN. A delay between the SWESMAN signal and the excitation current was found. We conjecture that this delay originates from the propagation distance of sonic waves emitted by magnetically stimulated particles. We examine the possibility of using the signal delay in practical applications.