Bandpass sorting of heterogeneous cells using a single surface acoustic wave transducer pair

Abstract

Separation and sorting of biological entities (viruses, bacteria, and cells) is a critical step in any microfluidic lab-on-a-chip device. Acoustofluidics platforms have demonstrated their ability to use physical characteristics of cells to perform label-free separation. Bandpass-type sorting methods of medium-sized entities from a mixture have been presented using acoustic techniques; however, they require multiple transducers, lack support for various target populations, can be sensitive to flow variations, or have not been verified for continuous flow sorting of biological cells. To our knowledge, this paper presents the first acoustic bandpass method that overcomes all these limitations and presents an inherently reconfigurable technique with a single transducer pair for stable continuous flow sorting of blood cells. The sorting method is first demonstrated for polystyrene particles of sizes 6, 10, and 14.5 μm in diameter with measured purity and efficiency coefficients above 75 ± 6% and 85 ± 9%, respectively. The sorting strategy was further validated in the separation of red blood cells from white blood cells and 1 μm polystyrene particles with 78 ± 8% efficiency and 74 ± 6% purity, respectively, at a flow rate of at least 1 μl/min, enabling to process finger prick blood samples within minutes.

Automated Particle and Cell Phenotyping Using Object Recognition and Tracking Based on Machine Learning Algorithms

“…where ( 2) is used for a static standing wave and (3) for frequency modulated standing waves. The parameter 𝑘 𝑦 is the horizontal wavenumber, 𝑦 0 the initial position, 𝛾 the ratio of peak acoustic and viscous forces, Δ𝜔 the frequency difference between the two transducers and 𝑄 = √(Δω) 2 − 𝛾 2 [5][6][7][8]. The constant 𝑐 1 is used to satisfy initial conditions.…”

Surface acoustic wave based microfluidic devices for biological applications

“…The resonant frequency of SSAW was about 12.98 MHz and the pressure nodes were designed to be close to the side of the channel. Simon et al 64 developed the bandpass sorting method, where a middle-sized particle was selected in two steps (Fig. 5b).…”

Recent advances in acoustofluidic separation technology in biology

“… Type of acoustic waves Typical exciter Features of devices Ref. Bulk acoustic waves Piezoelectric material Easy to fabricate, but difficult to manipulate pressure nodes and antinodes 71 , 82 Traveling surface acoustic waves One IDT Flexible to manipulate and generate acoustic streaming 43 , 73 Standing surface acoustic waves A pair of opposing IDTs Convenient control of pressure nodes and anti-nodes 42 , 69 , 72 Tilted-angle traveling surface acoustic waves One IDT with tilted-angle along the channel Increased migration distance of target particles 60 Tilted-angle standing surface acoustic waves A pair of opposing IDTs with tilted-angle along the channel Long distance migration and stable separation for multiple particles 63 , 74 …”

“…Because the ARF acting on particles is proportional to the particle size, it is natural to use acoustic waves to separate particles of different sizes. Many acoustofluidic devices 42 – 45 have been developed based on this separation principle. However, other factors, such as the structure and position of IDTs, can affect the outcomes in size-based separation.…”