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Centrifugal separation is a highly efficient technique for accelerating the sedimentation of blood constituents in a cylindrical container through high-speed spin-up rotation. Few studies have reported on the separation of different blood constituents from homogeneous mixture of whole blood. In this study, the process through which blood constituent sedimentation occurs in a spin-up rotating cylindrical container is numerically investigated. Whole blood is considered a homogeneous mixture of red blood cells (RBC) and plasma, which are both considered incompressible viscous liquids. The Euler multi-fluid VOF (volume of fluid) model is introduced to simulate the separation of RBCs and plasma. The effects of the rotation speed and the geometric construction of the cylindrical container on the sedimentation and stratification of different blood constituents are studied. A stable interface between the RBC layer and plasma layer forms earlier in a high position. With an increase in the rotation speed, the interface between the RBCs and plasma layers forms more quickly. In the cylindrical container with a helical groove on the outer wall, a stable vortex occurs near the groove, which forces red blood cells to move toward the lower location of the groove, resulting in a conical distribution of the RBC layer and a larger volume fraction of plasma near the exit at the top. This allows for sufficient precipitation of the plasma, improving the separation efficiency.

Microplastics have emerged as ubiquitous contaminants, attracting increasing global attention. Recent evidence confirms the presence of microplastics in human blood, suggesting their potential to interact with cells and induce adverse physiological reactions in various organs as blood circulates. To quantify the distribution of microplastics and assess their potential effects on human health, the effective separation of microplastics from blood is crucial. However, current methods for separating microplastics from blood are limited in effectiveness and simplicity. This study proposes a microfluidic device that utilizes traveling surface acoustic waves to separate microplastics from blood. While traveling surface acoustic waves have been employed to separate various particles, a systematic study on the separation of microplastics from blood samples has not been previously reported. Specifically, the theoretical values of the acoustic radiation factor for various types of microplastics and blood cells were investigated. The significant differences in resonant frequencies indicated the feasibility of separating microplastics of different sizes and types from blood cells. Experimental validation was performed using a polydimethylsiloxane microfluidic device on a piezoelectric lithium niobate substrate. The device successfully separated 5- and 10-micrometer polystyrene microplastics from blood samples. The effects of power and flow rate on separation efficiency were also systematically investigated. This study provides a novel approach for the effective separation of microplastics from blood, contributing to the assessment of their distribution and potential health impacts.

The separation of bio-suspensions, such as blood, is of great interest for many biomedical applications, such as the extraction of leucocytes from whole blood, the laboratory analysis of specific cells or a mixed cell suspensions from bioreactors or the preparation of cellular products for cellbased therapy. In particular, mechanical separation processes have been established for the rapid separation of biosuspensions. The principle of mechanical separation is based on the specific density of the particles or the particle size. Thus, the corresponding processes are based on centrifugation and/or filtration. The standard process to prepare blood products from whole blood donations contains several steps. First the blood is separated into different phases by centrifugation and then further separated by filters containing specific filtration layers. The shortcomings of this process is the low yield due to bio-particles remaining in the filter and the high costs for equipment due to the use of multiple devices for centrifugation and filtration. Here we present the proof of principle of an adaptive, size-selective filter that addresses the above mentioned shortcomings. The filter is designed to combine the filtration and centrifugation process within one step. Therefore a novel filtration device was designed that can be used within a standard centrifugation tube. During centrifugation, the centrifugal force changes the filtration coefficient of the filter. This can be used to separate different sized of bio-particles at different centrifugation speeds. Moreover, the cells that were hold back in the filter can be removed afterwards by increasing the centrifugation speed. In this way, the filter is created to gradually release cells of a specific size yielding in a high purity of different cell fractions.

In this paper, we report a point-of-care (POCT) testing strip based on a porous membrane structure for whole blood separation and colorimetric analysis without external supporting equipment. Conventional blood tests rely on large instruments for blood pretreatment and separation to improve measurement accuracy. Cellulose acetate (CA) membranes with different pore diameters and structures were prepared via a non-solvent method for the separation of whole blood. Among them, CA@PEG-2000 membranes with nano-pores on the surface and micro-pores in the interior facilitated the capture of blood cells on the surface, as well as the free diffusion of plasma through the porous interior structure. The fluid flow of blood in the asymmetric porous structure can be theoretically estimated using the Lucas-Washburn equation. Compared with the conventional paper strips and other porous membranes, the CA@PEG-2000 membrane with an immobilized sensing layer exhibited efficient blood separation, a short response time (less than 2 min), an ultralow dosage volume (5 μL), and high sensitivity. The fabricated blood separation membranes can be further used for the detection of various biomarkers in whole blood, providing additional options for rapid quantitative POCT tests.

In this paper, we describe two fabrication methods (well array-based and biopsy punching-based) of gel disks to construct a gel-based point-of-care (POC) diagnosis device for direct colorimetric measurement of human whole blood glucose without any extra blood separation step. The gel disks are made of Polyethylene glycol (PEG) diacrylate (PEG-DA) containing immobilized glucose colorimetric assay reagents. The performances of three types of PEG-DA gel (molecular weight: 575, 3,400, and 10,000) based sensors as well as the two fabrication methods were investigated. • The fabricated devices enabled colorimetric whole blood glucose sensing assay without the need for blood cell separation • The biopsy punching-based gel disk fabrication method provided less variation on the fabricated gel disks

A microfluidic chip, which can separate and enrich leukocytes from whole blood, is proposed. The chip has 10 switchback curve channels, which are connected by straight channels. The straight channels are designed to permit the inertial migration effect and to concentrate the blood cells, while the curve channels allow the Dean flow to further classify the blood cells based on the cell sizes. Hydrodynamic suction is also utilized to remove smaller blood cells (e.g., red blood cell (RBC)) in the curve channels for higher separation purity. By employing the inertial migration, Dean flow force, and hydrodynamic suction in a continuous flow system, our chip successfully separates large white blood cells (WBCs) from the whole blood with the processing rates as high as 1 × 108 cells/sec at a high recovery rate at 93.2% and very few RBCs (~0.1%).

Blood, a complex biological fluid, comprises 45% cellular components suspended in protein rich plasma. These different hematologic components perform distinct functions in vivo and thus the ability to efficiently fractionate blood into its individual components has innumerable applications in both clinical diagnosis and biological research. Yet, processing blood is not trivial. In the past decade, a flurry of new microfluidic based technologies has emerged to address this compelling problem. Microfluidics is an attractive solution for this application leveraging its numerous advantages to process clinical blood samples. This paper reviews the various microfluidic approaches realized to successfully fractionate one or more blood components. Techniques to separate plasma from hematologic cellular components as well as isolating blood cells of interest including certain rare cells are discussed. Comparisons based on common separation metrics including efficiency (sensitivity), purity (selectivity), and throughput will be presented. Finally, we will provide insights into the challenges associated with blood-based separation systems towards realizing true point-of-care (POC) devices and provide future perspectives.