How can sound be used to move cells?
Sound is created when a vibration generates pressure waves that propagate through a medium. When the wave encounters a particle, the particle is moved by the acoustic forces generated by the wave.
In acoustofluidics, ultrasound is used to create standing acoustic waves in microfluidic channels. The standing wave typically focuses the particles towards the pressure node, where the pressure variation is the lowest.
The sound frequency is similar to diagnostic ultrasound and has been shown to be very gentle to biological samples, with no activation or decrease in viability.
Acoustofluidics can be implemented in two different ways, acoustic separation and acoustic trapping.