Acoustophoresis of non-spherical microparticles using strong resonant acoustic fields of asymmetric acoustofluidic devices

Acoustofluidic devices use ultrasound to create a force field for manipulation of particles in microchannels. We present a combined numerical and experimental method for design and characterization of asymmetric microfluidic chips capable of exciting acoustic resonances that are stronger by two orders of magnitude compared to their more common symmetric counterparts. Properly damped, multiphysics simulations of silicon-glass devices capture the complex interplay of physical phenomena leading to development of robust acoustophoresis that is crucial for rapid assembly of microparticle structures. Numerical models of isolated non-spherical microparticles show a variance in acoustic force of up to 50 percent based on particle orientation and aspect ratio alone. Calculated acoustic torque emphasizes that suspended non-spherical particles have a single preferred orientation depending on their geometry. These findings offer insight and an added layer of control for generating more complex micro-assemblies using acoustofluidics. This information is critical for technologies that benefit from gentle and robust handling of microparticles for applications like additive manufacturing and bio 3D printing.