Fig. 4: Trapping and transport mechanism.
From: Acoustic microbubble propulsion, train-like assembly and cargo transport
The schematic and image sequences demonstrate (a) bubble train propulsion and simultaneous trapping of solid particles at the center point between adjacent microbubbles. b The transport and release of microparticles at 2.5 s when the acoustic field is deactivated. Microbubbles emerge from a narrow slit leaving solid particles behind. c The trapping, transport, and release of yeast cells, at 3.5 s when the acoustic field is deactivated. d A solid microparticle bounded by two oscillating bubbles in an acoustic field. e Force field experienced by the microparticle was calculated using the following parameters. The equilibrium bubble radii are \({R}_{10}={R}_{20}=25\) μm. The distance between the bubbles’ surfaces is 15 μm. The bubbles oscillate at 23 kHz. The particle, with radius \({R}_{p}=5\) μm, is made of polystyrene, whose density and sound speed are \({\rho }_{p}=1060\) kg/m3 and cp = 2350 m/s. The sound speed in the liquid is c = 1450 m/s. The liquid density is \({\rho }_{0}=1086\) kg/m3. f Acoustic streamlines created by oscillation of a pair of discoidal microbubbles illustrates the repulsion between them.
