Nonlinear acoustic characteristics of multilayer magnetic microbubbles

The combination of superparamagnetic iron oxide nanoparticles (SPIOs) with ultrasonic contrast agent (UCA) microbubble is called magnetic (MMB) and has been used to produce multimodal agents enhance medical ultrasound resonance imaging. are either covalently linked the shell or physically entrapped into shell. Considering effect volume fraction SPIOs on density viscosity, a nonlinear dynamic equation microbubbles (MMBs) multilayer membrane structure constructed based basic theory bubble dynamics. influences driving sound pressure frequency, particle fraction, thickness surface tension acoustic-dynamics behavior numerically analyzed. results show that when particles small <i>α</i> ≤ 0.1, acoustic properties similar those ordinary UCA microbubbles. response depends its initial size pressure. critical vibration instability lowest field frequency twice <i>f</i><sub>0</sub> (<i>f</i> = 2<i>f</i><sub>0</sub>). presence inhibits bubbles from expanding contracting, but inhibition very limited. parameter <i>K</i> outer film material also affect microbubble. When 0.2–0.4 N/m 50–150 nm respectively, it observed an unstable region.