Continuous separation of particles in a PDMS microfluidic channel via travelling surface acoustic waves (TSAW)

Abstract

We demonstrate a simple and efficient device for the continuous label-free separation of microparticles using travelling surface acoustic waves (TSAW). A focusing interdigitated unidirectional transducer released high frequency (133.3 MHz) TSAW normal to the fluid flow direction to segregate 3 μm particles from 10 μm particles with a separation efficiency of 100%. The TSAW based separator does not necessitate a tight alignment of the PDMS microchannel with the transducer.

Vertical Hydrodynamic Focusing and Continuous Acoustofluidic Separation of Particles via Upward Migration

“…Among the single‐layered PDMS‐based devices, similar kind of focusing is not reported before. Due to the utilization of the principal component of ARF, the present device successfully operated for particle separation at net flow rate up to 1.3 mL min −1 , which is ≈100 times higher than used in previously reported SAW devices 20, 23, 31, 32, 37, 38, 42, 43, 47, 48. The throughput of the proposed device can be further improved with ease by increasing the width of the microchannel since the microchannel is placed directly on the IDT.…”

“…Compared with the most SSAW‐based devices23, 39, 40 that usually require a pair of parallel IDTs tightly aligned with the microchannel, the present device did not require tight alignment with the microchannel similar to other TSAW‐based devices 20, 38. However, tilted angle SSAWs have been utilized to circumvent such limitations 41.…”

“…Acoustophoresis‐based microfluidic separation techniques are preferred due to the contactless handling of the biological samples, low power requirement, and biocompatible nature of the acoustic waves, all of which permit incorporation of acoustophoresis techniques into microscale total analysis systems. Surface acoustic wave (SAW)‐based particle separation devices mostly feature a single‐layered polydimethylsiloxane (PDMS) microfluidic channel and a pair of interdigitated electrodes patterned onto a piezoelectric substrate that produces acoustic waves along the surface of the substrate to manipulate the suspended micro‐objects 17, 18, 19, 20…”

“…Collins et al33 took advantage of the vertical component of the ARF and employed a focused IDT to trap and concentrate selected particles behind a microfabricated PDMS membrane. However, the particle trapping capacity of the membrane would reach a saturation value in a short period of time; therefore, a continuous flow separation device offers improved particle separation performance 20, 23…”

Continuously phase-modulated standing surface acoustic waves for separation of particles and cells in microfluidic channels containing multiple pressure nodes

“…Recently, particle manipulation using surface acoustic waves (SAW) is emerging because of its high energy efficiency, label-free characteristics, and applicability to sound-absorbing materials such as polydimethylsiloxane (PDMS) [6]. Two major types of SAW are travelling SAW (TSAW) and standing SAW (SSAW), both of which are shown to have the ability to separate particles [7][8][9][10][11][12][13][14].…”