Double-Mode Microparticle Manipulation by Tunable Secondary Flow in Microchannel With Arc-Shaped Groove Arrays

Investigation of particle manipulation mechanism and size sorting strategy in a double-layered microchannel

Traditionally, comprehensive laboratorial experiments on newly proposed microfluidic devices are necessary for theoretical validation, technological design, methodological calibration and optimization. Multiple parameters and characteristics, such as the flow rate, particle size, microchannel dimensions, etc., should be studied by controlled trials, which could inevitably result in extensive experiments and a heavy burden on researchers. In this work, a novel numerical model was introduced to simulate particle migration within a complicated double-layered microchannel. Using the hybrid meshing method, the proposed model achieved a significant improvement in meshing quality, and remarkably reduced the required calculation resources at the same time. The robust, efficient and resource-saving numerical model was calibrated and validated with experimental results. Based on this model, 1) the mechanism of microparticle manipulation within the microchannel was revealed; 2) the primary reason for the microparticle focusing failure was investigated; and 3) the optimal microparticle sorting strategy at different flow rates was analyzed. In experiments, the obtained optimal strategy could approach a good sorting performance with a high recovery rate and high concentration ratio in a high-throughput manner. The proposed numerical model shows great potential in mechanism investigation and functional prediction for microfluidic technologies using unconventional designs.

Biomedical Applications of Microfluidic Devices: A Review

Both passive and active microfluidic chips are used in many biomedical and chemical applications to support fluid mixing, particle manipulations, and signal detection. Passive microfluidic devices are geometry-dependent, and their uses are rather limited. Active microfluidic devices include sensors or detectors that transduce chemical, biological, and physical changes into electrical or optical signals. Also, they are transduction devices that detect biological and chemical changes in biomedical applications, and they are highly versatile microfluidic tools for disease diagnosis and organ modeling. This review provides a comprehensive overview of the significant advances that have been made in the development of microfluidics devices. We will discuss the function of microfluidic devices as micromixers or as sorters of cells and substances (e.g., microfiltration, flow or displacement, and trapping). Microfluidic devices are fabricated using a range of techniques, including molding, etching, three-dimensional printing, and nanofabrication. Their broad utility lies in the detection of diagnostic biomarkers and organ-on-chip approaches that permit disease modeling in cancer, as well as uses in neurological, cardiovascular, hepatic, and pulmonary diseases. Biosensor applications allow for point-of-care testing, using assays based on enzymes, nanozymes, antibodies, or nucleic acids (DNA or RNA). An anticipated development in the field includes the optimization of techniques for the fabrication of microfluidic devices using biocompatible materials. These developments will increase biomedical versatility, reduce diagnostic costs, and accelerate diagnosis time of microfluidics technology.

A single-view field filter device for rare tumor cell filtration and enumeration

In this work, we demonstrate a single-view field filter (SVFF) device for the efficient filtration and enumeration of rare tumor cells in the blood. In our device, the track-etched membrane is integrated within a low-cost polymer-film microfluidic chip, and multiplex microfiltration chambers are designed. Our device permits the performing of multiple sample tests on a single membrane and the dynamical observation of the entire filtration process in a single field of view. To characterize the device performance, our device is first tested using tumor cells, and three different cell behaviors are observed during the filtration process. Finally, we successfully apply our device for the separation of rare tumor cells from the lysed blood samples at various flow rates. The recovery rates of 93.3, 87.6, and 84.1% can be respectively achieved at the throughputs of 50, 100, and 150 μL/min. Our single-view field filter (SVFF) device offers the advantages of label-free filtration, efficient enumeration, easy integration, and low cost, and holds the potential to be used as an efficient tool for the filtration and enumeration of rare cells.

A Review of Secondary Flow in Inertial Microfluidics

Inertial microfluidic technology, which can manipulate the target particle entirely relying on the microchannel characteristic geometry and intrinsic hydrodynamic effect, has attracted great attention due to its fascinating advantages of high throughput, simplicity, high resolution and low cost. As a passive microfluidic technology, inertial microfluidics can precisely focus, separate, mix or trap target particles in a continuous and high-flow-speed manner without any extra external force field. Therefore, it is promising and has great potential for a wide range of industrial, biomedical and clinical applications. In the regime of inertial microfluidics, particle migration due to inertial effects forms multiple equilibrium positions in straight channels. However, this is not promising for particle detection and separation. Secondary flow, which is a relatively minor flow perpendicular to the primary flow, may reduce the number of equilibrium positions as well as modify the location of particles focusing within channel cross sections by applying an additional hydrodynamic drag. For secondary flow, the pattern and magnitude can be controlled by the well-designed channel structure, such as curvature or disturbance obstacle. The magnitude and form of generated secondary flow are greatly dependent on the disturbing microstructure. Therefore, many inventive and delicate applications of secondary flow in inertial microfluidics have been reported. In this review, we comprehensively summarize the usage of the secondary flow in inertial microfluidics.