Issue 9, 2009

Soft inertial microfluidics for high throughput separation of bacteria from human blood cells

Abstract

We developed a new approach to separate bacteria from human blood cells based on soft inertial force induced migration with flow defined curved and focused sample flow inside a microfluidic device. This approach relies on a combination of an asymmetrical sheath flow and proper channel geometry to generate a soft inertial force on the sample fluid in the curved and focused sample flow segment to deflect larger particles away while the smaller ones are kept on or near the original flow streamline. The curved and focused sample flow and inertial effect were visualized and verified using a fluorescent dye primed in the device. First the particle behaviour was studied in detail using 9.9 and 1.0 µm particles with a polymer-based prototype. The prototype device is compact with an active size of 3 mm2. The soft inertial effect and deflection distance were proportional to the fluid Reynolds number (Re) and particle Reynolds number (Rep), respectively. We successfully demonstrated separation of bacteria (Escherichia coli) from human red blood cells at high cell concentrations (above 108/mL), using a sample flow rate of up to 18 µL/min. This resulted in at least a 300-fold enrichment of bacteria at a wide range of flow rates with a controlled flow spreading. The separated cells were proven to be viable. Proteins from fractions before and after cell separation were analyzed by gel electrophoresis and staining to verify the removal of red blood cell proteins from the bacterial cell fraction. This novel microfluidic process is robust, reproducible, simple to perform, and has a high throughput compared to other cell sorting systems. Microfluidic systems based on these principles could easily be manufactured for clinical laboratory and biomedical applications.

Graphical abstract: Soft inertial microfluidics for high throughput separation of bacteria from human blood cells

Article information

Article type
Paper
Submitted
07 Oct 2008
Accepted
21 Jan 2009
First published
13 Feb 2009

Lab Chip, 2009,9, 1193-1199

Soft inertial microfluidics for high throughput separation of bacteria from human blood cells

Z. Wu, B. Willing, J. Bjerketorp, J. K. Jansson and K. Hjort, Lab Chip, 2009, 9, 1193 DOI: 10.1039/B817611F

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