Microdevice For Separation Research Articles

Numerical simulation of novel gas separation microdevice with oscillating elements

Present paper uses Direct Simulation Monte Carlo method to perform a numerical study of a new MEMS-based gas separation device prototype. The core part of the device is represented by a microchannel with a row of elements-barriers oscillating with high frequency perpendicular to channel axis and periodically blocking the flow. The influence of practical aspects (device geometry, arrangement of phases of barriers oscillation, gas leakage and etc.) on separation performance was investigated. It is demonstrated that separation factor of the device can approach values of free-molecular (Knudsen) diffusion at any rate of gas rarefaction (defined by Knudsen number) and feasible barriers oscillation frequency (below 10 kHz) given that the necessary number of barriers is used in the device. Moreover, it was shown that in case of partial sampling of gas at the outlet, separation factor of the device can increase significantly beyond the Knudsen diffusion limit.

A circular gradient-width crossflow microfluidic platform for high-efficiency blood plasma separation

Separation and collection of blood plasma are required steps for broad ranges of clinical diagnostic assays. Here, we introduce a continuous-flow blood plasma separation microfluidic device based on size exclusion cell separation in crossflow microchannels. A gradient-width crossflow microchannel structure is utilized to minimize blood cell leakage into the plasma collection channel while maximizing the flow rate for higher throughput. Additionally, the crossflow channels are placed at the corner of the blood channel to enhance Fahraeus effects, resulting in reduction of the concentration of blood cells around the entrance of the crossflow channels. Combined with a circular geometry that minimizes the footprint of the device for point-of-care diagnosis applications, the developed device significantly improves the performance of blood plasma separation in terms of separation efficiency, degree of hemolysis, and microchannel clogging by blood cells. At a relatively high flow rate of 2000 µl/h for a passive blood separation device, a plasma extraction ratio of 22% and red blood cell separation efficiency of 97% could be achieved using undiluted whole human blood, where such separation efficiency is about 28% higher compared with that of a conventional crossflow design. The effect of channel height and flow rate on the degree of hemolysis was also investigated, where the optimized device could achieve very little hemolysis (0.01–0.5%), demonstrating that the device can produce high-quality blood plasma. Integration of this high-performance, compact, and passive blood plasma separation microdevice with on-chip blood biomarker sensing elements can create a point-of-care diagnosis system with reduced cost, test time, and sample/reagent volume.

Design and Verification of a Blood Cell Separation Microfluidic Device

Blood cell separation microdevices are designed in biomedical engineering for the separation of particular cells from blood, such as cancer cells. The movement of blood microparticles, specially these cancer cells, in a continuous flow microfluidic device is controlled by several forces, as a result, understanding and guiding the movement of these microparticles is a challenging problem. These cells are subject to different types of forces that result from natural or external effects. These forces include gravity, and virtual mass, buoyancy, dielectrophoresis and, inertia force. Therefore, all of these are to be accounted for in any design or implementation of a system. This paper we use formal analysis of a separation microdevice in order to model and verify the the microparticle movement and behavior at high level of abstraction while considering different types of forces. The the dynamic behavior of the particle can be modeled as a Markovian decision process in order to predict the trajectory of microparticles. This model can be used to provide probabilistic analysis for the particle movement in the microdevice under the effect of different types of forces.

Formal Verification of a Microfluidic Device for Blood Cell Separation

Blood cell separation microdevices are designed in biomedical engineering for separation of cancer cells from blood. The movement of cancer cells particles in a continuous flow microfluidic device is a challenging problem since there are several forces incorporated. For instance, forces due to inertia, gravity, buoyancy, dielectrophoresis and virtual mass are accounted for in this system. Understanding the cell particle movement and behavior at high level of abstraction is necessary in order to avoid fundamental errors in the design of systems that can make use of this behavior. In this paper we use formal analysis in order to formalize and validate the movement of microparticles under DEP forces for blood cell separation microdevice. This is achieved by modeling the dynamic behavior that can predict the trajectory of microparticles as a transition state based system. The model is used to validate the correctness of the microdevice at early stages of the design process.

Microdevice for Separation of Circulating Tumor Cells using Embedded Magnetophoresis with V-shaped Ni-Co Nanowires and Immuno-nanomagnetic Beads

The novelty of this study resides in a 6”-wafer-level microfabrication protocol for a microdevice with a fluidic control system for the separation of circulating tumor cells (CTCs) from human whole blood cells. The microdevice utilizes a lateral magnetophoresis method based on immunomagnetic nanobeads with anti-epithelial cell adhesive molecule antibodies that selectively bind to epithelial cancer cells. The device consists of a top polydimethylsiloxane substrate for microfluidic control and a bottom substrate for lateral magnetophoretic force generation with embedded v-shaped soft magnetic microwires. The microdevice can isolate about 93% of the spiked cancer cells (MCF-7, a breast cancer cell line) at a flow rate of 40/100 mL/min with respect to a whole human blood/buffer solution. For all isolation, it takes only 10 min to process 400 mL of whole human blood. The fabrication method is sufficiently simple and easy, allowing the microdevice to be a mass-producible clinical tool for cancer diagnosis, prognosis, and personalized medicine.

A microfluidic device for continuous manipulation of biological cells using dielectrophoresis

The present study demonstrates the design, simulation, fabrication and testing of a label-free continuous manipulation and separation micro-device of particles/biological cells suspended on medium based on conventional dielectrophoresis. The current dielectrophoretic device uses three planner electrodes to generate non-uniform electric field and induces both p-DEP and n-DEP force simultaneously depending on the dielectric properties of the particles and thus influencing at least two types of particles at a time. Numerical simulations were performed to predict the distribution of non-uniform electric field, DEP force and particle trajectories. The device is fabricated utilizing the advantage of bonding between PDMS and SU8 polymer. The p-DEP particles move away from the center of the streamline, while the n-DEP particles will follow the central streamline along the channel length. Dielectrophoretic effects were initially tested using polystyrene beads followed by manipulation of HeLa cells. In the experiment, it was observed that polystyrene beads in DI water always response as n-DEP up to 1MHz frequency, whereas HeLa cells in PBS medium response as n-DEP up to 400kHz frequency and then it experiences p-DEP up to 1MHz. Further, the microscopic observations of DEP responses of HeLa cells were verified by performing trapping experiment at static condition.

Basic Structure and Cell Culture Condition of a Bioartificial Renal Tubule on Chip towards a Cell-based Separation Microdevice

Various separation processes have been integrated in microfluidics, such as capillary electrophoresis and chromatography, on a microchip. However, it is extremely difficult to separate a complicated biological system by conventional methods. Here, we report on a feasible structure and the culture condition of human renal proximal tubule epithelial cells (RPTECs), with the aim to construct a bioartificial renal tubule on a chip. Glass microchips and a polycarbonate membrane were sealed with no leakage after a surface modification. Furthermore, matrigel was selected as an optimized extracellular matrix (ECM) for cell-proliferation on the membrane. After culturing for 5 days, RPTECs reached confluent in the chip-membrane structure, which was confirmed by nuclei staining. So far, we have constructed the basic structure and cell proliferation circumstance for the future demonstration of the RPTECs separating function. This separation microdevice has promising potential to be applied as both a unit of a circulation cell culture system and a research platform of cell biology.

Microdevices for separation, accumulation, and analysis of biological micro- and nanoparticles

Microfabrication and performance of a novel microsystem for separation, accumulation and analysis of biological micro- and nanoparticles is reported. Versatile chip functions based on dielectrophoresis and microfluidics were integrated to isolate particles from complex sample solutions such as serum. A bead-based assay for virus detection is proposed. Separation of micro- and sub-mum beads employing dielectrophoretic deflector and bandpass structures is demonstrated. Individual antibody coated beads with hepatitis A virus bound to their surface were trapped by negative dielectrophoresis in a field cage and analysed by fluorescence microscopy.