Inertial focusing of microparticles, bacteria, and blood in serpentine glass channels

Abstract

Early detection of pathogenic microorganisms is pivotal to diagnosis and prevention of health and safety crises. Standard methods for pathogen detection often rely on lengthy culturing procedures, confirmed by biochemical assays, leading to >24 h for a diagnosis. The main challenge for pathogen detection is their low concentration within complex matrices. Detection of blood‐borne pathogens via techniques such as PCR requires an initial positive blood culture and removal of inhibitory blood components, reducing its potential as a diagnostic tool. Among different label‐free microfluidic techniques, inertial focusing on microscale channels holds great promise for automation, parallelization, and passive continuous separation of particles and cells. This work presents inertial microfluidic manipulation of small particles and cells (1–10 μm) in curved serpentine glass channels etched at different depths (deep and shallow designs) that can be exploited for (1) bacteria preconcentration from biological samples and (2) bacteria‐blood cell separation. In our shallow device, the ability to focus Escherichia coli into the channel side streams with high recovery (89% at 2.2× preconcentration factor) could be applied for bacteria preconcentration in urine for diagnosis of urinary tract infections. Relying on differential equilibrium positions of red blood cells and E. coli inside the deep device, 97% red blood cells were depleted from 1:50 diluted blood with 54% E. coli recovered at a throughput of 0.7 mL/min. Parallelization of such devices could process relevant volumes of 7 mL whole blood in 10 min, allowing faster sample preparation for downstream molecular diagnostics of bacteria present in bloodstream.

Tuning particle inertial separation in sinusoidal channels by embedding periodic obstacle microstructures

“…Four typical geometries have been extensively studied for inertial focusing and separation, including straight, 38,39 expansioncontraction, 40,41 spiral 42,43 and serpentine channels. 44,45 Microfluidic devices based on these channel geometries have been studied and applied for a wide range of biomedical applications such as blood cells separation, 46 isolation of circulating tumour cells (CTCs), 47 bacteria separation, 48 algae sorting, 49 plasma extraction 50 and solution exchange. 51 To further leverage secondary flows in inertial microfluidics, innovative channel designs that combine two or more geometric features have been explored.…”

Investigation of Multidimensional Fractionation in Microchannels Combining a Numerical DEM-LBM Approach with Optical Measurements

“…Still the use of serpentine channels for the manipulation of microparticles is very attractive, as the channels have a simple linear structure (relatively easy fabrication and parallelization), do not rely on external forces and have proven to work with model particles as well as with cells (see e.g., [4,61,[63][64][65]). All this makes serpentine channels very attractive, which is why they are the subject of current research.…”

High-throughput particle focusing and separation in split-recombination channel

“…is the hydraulic diameter of the channel, where H ch and W ch are the channel height and width respectively. Normally, inertial microfluidic works with an intermediate Reynolds number regime (∼1 < Re < ∼100) [31].…”

“…Huang et al [30] investigated the focusing and separation of human breast cancer cells from the diluted blood under a throughput of 400 µl min −1 using the spiral channel. However, the major drawback of the spiral channel is the difficulty of arranging them in parallel on a single substrate, resulting in a low throughput [31]. Given that, a serpentine channel with alternating curvatures in series is often proposed to focus particles [31,32], circulating tumor cells (CTCs) [33,34], exosome [35] and bacteria [36,37] due to its combined effects of inertial lift force, Dean drag force and particle centrifugal force.…”

“…However, the major drawback of the spiral channel is the difficulty of arranging them in parallel on a single substrate, resulting in a low throughput [31]. Given that, a serpentine channel with alternating curvatures in series is often proposed to focus particles [31,32], circulating tumor cells (CTCs) [33,34], exosome [35] and bacteria [36,37] due to its combined effects of inertial lift force, Dean drag force and particle centrifugal force. Moreover, the combination of straight and curved channels is another appealing method to focus and separation particles.…”