Model for tracing the path of microparticles in continuous flow microfluidic devices for 2D focusing via standing acoustic waves

• Trajectory of microparticles in microfluidic layered transducer is modelled.
• Forces due to inertia, gravity, buoyancy, virtual mass and acoustics are accounted.
• Steady state levitation depends on acoustic energy density and wavelength.
• Steady state levitation is free of microparticle radius, initial location and flow rate.
• Transient levitation is influenced by all operating and geometric parameters.

An, experimentally validated, two-dimensional dynamic model for tracing the path of microparticles in a microfluidic layered transducer is developed. The model is based on Newton’s 2nd law and considers forces due to inertia, gravity, buoyancy, virtual mass and acoustics; it is solved using finite difference method. Microparticles’ trajectory consists of transient and steady state phases. All operating and geometric parameters are influential during the transient phase. The final levitation height is independent of the radius and initial vertical location of the microparticle as well as volumetric flow rate; however, dependent on the acoustic energy density and wavelength. There exists a threshold acoustic energy density for levitating microparticles from a specific initial vertical displacement; analytical equation for determining this acoustic energy density is provided.