Two-stage microfluidic device for acoustic particle manipulation

In this paper, we introduce a novel surface acoustic wave (SAW) based two-stage microfluidic platform for continuous particle focusing and separation. The driving force is acoustic radiation force generated by surface acoustic waves in a microfluidic device over a piezoelectric substrate. The prominent features of this two-stage sorter are that particle focusing and separation are accomplished simultaneously and the sorter doesn't require the use of the sheath flow for positioning or aligning of particles, thereby decreasing the complexity. Moreover, no physical contact is needed between the ultrasonic transducer and the medium. The ultrasonic treatment has not been shown to damage cells or biological material as well. Prior to separation, the particles are lined up to the center of the channel in the first stage without adding any sheath flow. After passing the first stage, the larger particles move to the pressure node more quickly than the smaller particles according to the difference of the acoustic forces acting on them. As the acoustic force is proportional to the volume of the particles, the larger particles are subjected to larger acoustic force. Consequently, the flow focused particles are separated with different lateral displacement along the cross-section of the channel. In the present paper, we discuss our design and fabrication efforts as well as review state-of-the-art particles manipulation techniques that are currently employed.