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. 2017 Jan 1;27(1):015031.
doi: 10.1088/1361-6439/27/1/015031. Epub 2016 Nov 30.

Acoustofluidic bacteria separation

Sixing Li  1 , Fen Ma  2 , Hunter Bachman  3 , Craig E Cameron  4 , Xiangqun Zeng  2 , Tony Jun Huang  1   3
Affiliations

Acoustofluidic bacteria separation

Sixing Li et al. J Micromech Microeng. .

Abstract

Bacterial separation from human blood samples can help with the identification of pathogenic bacteria for sepsis diagnosis. In this work, we report an acoustofluidic device for label-free bacterial separation from human blood samples. In particular, we exploit the acoustic radiation force generated from a tilted-angle standing surface acoustic wave (taSSAW) field to separate E. coli from human blood cells based on their size difference. Flow cytometry analysis of the E. coli separated from red blood cells (RBCs) shows a purity of more than 96%. Moreover, the label-free electrochemical detection of the separated E. coli displays reduced non-specific signals due to the removal of blood cells. Our acoustofluidic bacterial separation platform has advantages such as label-free separation, high biocompatibility, flexibility, low cost, miniaturization, automation, and ease of in-line integration. The platform can be incorporated with an on-chip sensor to realize a point-of-care (POC) sepsis diagnostic device.

Keywords: Acoustofluidics; bacterial separation; standing surface acoustic wave (SSAW).

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Figures

Figure 1
Figure 1
Schematic of our acoustofluidic separation of E. coli from human blood samples using the taSSAW technique. Inset: a photograph of our acoustofluidic device.
Figure 2
Figure 2
Stacked fluorescence images showing the separation of 4.95 μm (green) and 0.97 μm (red) polystyrene microparticles: (a–b) When the taSSAW was off, both the 4.95 and 0.97 μm microparticles exited the microchannel through the lower outlet; (c–d) When the taSSAW was on, the 4.95 μm microparticles were forced to the upper outlet while the 0.97 μm microparticles remained in the lower outlet, resulting in size-dependent acoustic separation of the two types of microparticles.
Figure 3
Figure 3
Stacked micrographs showing the acoustofluidic separation of E. coli from RBCs. (a, c) Bright-field and (b, d) fluorescence images represent RBCs and E. coli, respectively. (a–b) When the taSSAW was not applied, RBCs and E. coli were collected together from the lower outlet in a mixture. (c–d) When the taSSAW was applied, RBCs were pushed to the upper outlet while E. coli were collected from the lower outlet.
Figure 4
Figure 4
Flow cytometry results of (a) the mixture sample (RBCs mixed with E. coli), (b) separated E. coli sample collected through the lower outlet, and (c) separated RBCs sample collected through the upper outlet. (d) Percentages of E. coli and RBCs in three samples.
Figure 5
Figure 5
Electrochemical detection of E. coli from the mixture sample and separated E. coli sample using square wave voltammetry (SWV).
See this image and copyright information in PMC

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