Acoustofluidic separation of micro and nanoparticles in Newtonian and non-Newtonian fluids: A review

Passive and active separation of microparticles has great importance in biological analysis, diagnostics, chemical processing, etc. Acoustofluidic separation is an active technique employed to isolate or sort micron-sized particles continuously. This technique has lower power consumption compared to other active approaches. Besides, it has good biocompatibility. In this review, recent advances in acoustofluidic particle separation are discussed. Bulk Acoustic Waves (BAWs) and Surface Acoustic Waves (SAWs) are introduced and the effective forces in Newtonian and non-Newtonian fluids are defined. It is revealed that SAW transducers have several advantages for the separation of particles in comparison with BAW ones. This review demonstrates that Polydimethylsiloxane (PDMS) is widely used to fabricate microfluidic devices in which acoustic waves are employed for sorting and manipulating microparticles. Different investigations considered the separation of microparticles by acoustic waves are compared and their characteristics are determined. Besides, the challenges and perspectives of the field are analyzed and discussed.