Enhancement of inflection point focusing and rare-cell separations from untreated whole blood

Multiparameter Mechanical Phenotyping for Accurate Cell Identification Using High-Throughput Microfluidic Deformability Cytometry

Mechanical phenotyping has been widely employed for single-cell analysis over recent years. However, most previous works on characterizing the cellular mechanical properties measured only a single parameter from one image. In this paper, the quasi-real-time multiparameter analysis of cell mechanical properties was realized using high-throughput adjustable deformability cytometry. We first extracted 12 deformability parameters from the cell contours. Then, the machine learning for cell identification was performed to preliminarily verify the rationality of multiparameter mechanical phenotyping. The experiments on characterizing cells after cytoskeletal modification verified that multiple parameters extracted from the cell contours contributed to an identification accuracy of over 80%. Through continuous frame analysis of the cell deformation process, we found that temporal variation and an average level of parameters were correlated with cell type. To achieve quasi-real-time and high-precision multiplex-type cell detection, we constructed a back propagation (BP) neural network model to complete the fast identification of four cell lines. The multiparameter detection method based on time series achieved cell detection with an accuracy of over 90%. To solve the challenges of cell rarity and data lacking for clinical samples, based on the developed BP neural network model, the transfer learning method was used for the identification of three different clinical samples, and finally, a high identification accuracy of approximately 95% was achieved.

A self-cleaning micro-fluidic chip biospired by the filtering system of manta rays

Size-based particle filtration has become indispensable in numerous biomedical and environmental applications. In this study, bioinspired by the filter-feeding mechanism (lobe filtration) of manta rays, we designed a U-shaped biomimetic gill rake filter that combined lobe filtration and Dean flow to filter monodisperse suspensions, bi-disperse suspensions and yeast cells. Compared with other equipment using the inertial focusing technology, our equipment can perform high-throughput (up to 8 mL min-1) and high-efficiency filtration of particles (maximum filtration efficiencies of 96.08% and 97.14% for 10 and 15 μm monodisperse suspensions at the optimum flow rate of 6 mL min-1). The complex velocity field of the micro-fluidic flow within the filter is numerically simulated, and in combination with experiments, a threshold for the flow rate is identified. When the inlet flow rate exceeds the threshold value, the efficiency of particle filtration is increased rapidly. Afterwards, by analysing the filtration mechanism, we develop three novel filtration processes. The equilibrium positions of the particles and yeast cells in the main channel are close to the outer wall at high flow rate, which diminishes the likelihood of particles and yeast cells entering the side channel. This configuration establishes a self-cleaning mechanism, ensuring prolonged and efficient operation of the filter with high-throughput processing. Furthermore, the influence of the filter lobe angle and channel width on the filtration efficiency and outlet flow rate ratio are explored, and an optimisation plan is prepared.

Particle Separation in a Microchannel with a T-Shaped Cross-Section Using Co-Flow of Newtonian and Viscoelastic Fluids

In this study, we investigated the particle separation phenomenon in a microchannel with a T-shaped cross-section, a unique design detailed in our previous study. Utilizing a co-flow system within this T-shaped microchannel, we examined two types of flow configuration: one where a Newtonian fluid served as the inner fluid and a viscoelastic fluid as the outer fluid (Newtonian/viscoelastic), and another where both the inner and outer fluids were Newtonian fluids (Newtonian/Newtonian). We introduced a mixture of three differently sized particles into the microchannel through the outer fluid and observed that the co-flow of Newtonian/viscoelastic fluids effectively separated particles based on their size compared with Newtonian/Newtonian fluids. In this context, we evaluated and compared the particle separation efficiency, recovery rate, and enrichment factor across both co-flow configurations. The Newtonian/viscoelastic co-flow system demonstrated a superior efficiency and recovery ratio when compared with the Newtonian/Newtonian system. Additionally, we assessed the influence of the flow rate ratio between the inner and outer fluids on particle separation within each co-flow system. Our results indicated that increasing the flow rate ratio enhanced the separation efficiency, particularly in the Newtonian/viscoelastic co-flow configuration. Consequently, this study substantiates the potential of utilizing a Newtonian/viscoelastic co-flow system in a T-shaped straight microchannel for the simultaneous separation of three differently sized particles.

A needle tip CCEA microfluidic device based on enhanced Dean flow for cell washing

Particle/cell washing is an essential technique in biological and clinical manipulations. Herein, we propose a novel circular contraction-expansion array (CCEA) microdevice. It can be directly connected to a needle tip without connection tubes. Its small size and centrosymmetric structure are beneficial to low sample consumption, high connection stability, and a wide application range. Computational fluid dynamics (CFD) simulation results show that the CCEA structure can produce a stronger Dean flow and lead to faster particle/cell focusing than the circle structure and CEA structure with the same length. Experimentally, an optimal flow rate ratio of 1:3 and an optimal total flow rate of 120 μL/min were found to ensure a stable fluid distribution. Under these conditions, rapid focusing of 10-20 μm particles with high efficiencies was achieved. Compared with a normal CEA device using tubes, the particle loss rate could be reduced from 64 to 7% when washing 500 μL of a rare sample. Cell suspensions with concentrations from 3 × 105/mL to 1 × 103/mL were tested. The high cell collection efficiency (>85% for three cell lines) and stable waste removal efficiency (>80%) reflected the universality of the CCEA microfluidic device. After the washing, the cell activities of H1299 cells and MCF-7 cells were calculated to be 93.8 and 97.5%, respectively. This needle-tip CCEA microfluidic device showed potential in basic medical research and clinical diagnosis.

Inertial microfluidics for high-throughput cell analysis and detection: a review

Since it was first proposed in 2007, inertial microfluidics has been extensively studied in terms of theory, design, fabrication, and application. In recent years, with the rapid development of microfabrication technologies, a variety of channel structures that can focus, concentrate, separate, and capture bioparticles or fluids have been designed and manufactured to extend the range of potential biomedical applications of inertial microfluidics. Due to the advantages of high throughput, simplicity, and low device cost, inertial microfluidics is a promising candidate for rapid sample processing, especially for large-volume samples with low-abundance targets. As an approach to cellular sample pretreatment, inertial microfluidics has been widely employed to ensure downstream cell analysis and detection. In this review, a comprehensive summary of the application of inertial microfluidics for high-throughput cell analysis and detection is presented. According to application areas, the recent advances can be sorted into label-free cell mechanical phenotyping, sheathless flow cytometric counting, electrical impedance cytometer, high-throughput cellular image analysis, and other methods. Finally, the challenges and prospects of inertial microfluidics for cell analysis and detection are summarized.

Size-tuneable isolation of cancer cells using stretchable inertial microfluidics

Inertial microfluidics is a simple, low cost, efficient size-based separation technique which is being widely investigated for rare-cell isolation and detection. Due to the fixed geometrical dimensions of the current rigid inertial microfluidic systems, most of them are only capable of isolating and separating cells with certain types and sizes. Herein, we report the design, fabrication, and validation of a stretchable inertial microfluidic device with a tuneable separation threshold that can be used for heterogenous mixtures of particles and cells. Stretchability allows for the fine-tuning of the critical sorting size, resulting in a high separation resolution that makes the separation of cells with small size differences possible. We validated the tunability of the separation threshold by stretching the length of a microchannel to separate the particle sizes of interest. We also evaluated the focusing efficiency, flow behaviour, and the positions of cancer cells and white blood cells (WBCs) in an elongated channel, separately. In addition, the performance of the device was verified by isolating cancer cells from WBCs which revealed a high recovery rate and purity. The stretchable chip showed promising results in the separation of cells with comparable sizes. Further validation of the chip using whole blood spiked with cancer cells delivered a 98.6% recovery rate with 90% purity. Elongating a stretchable microfluidic chip enables onsite modification of the dimensions of a microchannel leading to a precise tunability of the separation threshold as well as a high separation resolution.

Changes of Inertial Focusing Position in a Triangular Channel Depending on Droplet Deformability and Size

Studies on cell separation with inertial microfluidics are often carried out with solid particles initially. When this condition is applied for actual cell separations, the efficiency typically becomes lower because of the polydispersity and deformability of cells. Therefore, the understanding of deformability-induced lift force is essential to achieve highly efficient cell separation. We investigate the inertial focusing positions of viscous droplets in a triangular channel while varying Re, deformability, and droplet size. With increasing Re and decreasing droplet size, the top focusing position splits and shifts along the sidewalls. The threshold size of the focusing position splitting increases for droplets with larger deformability. The overall path of the focusing position shifts with increasing Re also has a strong dependency on deformability. Consequently, droplets of the same size can have different focusing positions depending on their deformability. The feasibility of deformability-based cell separation is shown by different focusing positions of MCF10a and MCF7 cells.