Continuous Submicron Particle Separation Via Vortex-Enhanced Ionic Concentration Polarization: A Numerical Investigation

Microstructured Porous Capacitive Bio-pressure Sensor Using Droplet-based Microfluidics

Background

Devices that mimic the functions of human skin are known as "electronic skin," and they must have characteristics like high sensitivity, a wide dynamic range, high spatial homogeneity, cheap cost, wide area easy processing, and the ability to distinguish between diverse external inputs.

Methods

This study introduces a novel approach, termed microfluidic droplet-based emulsion self-assembly (DMESA), for fabricating 3D microstructured elastomer layers using polydimethylsiloxane (PDMS). The method aims to produce accurate capacitive pressure sensors suitable for electronic skin (e-skin) applications. The DMESA method facilitates the creation of uniform-sized spherical micropores dispersed across a significant area without requiring a template, ensuring excellent spatial homogeneity.

Results

Micropore size adjustment, ranging from 100 to 600 μm, allows for customization of pressure sensor sensitivity. The active layer of the capacitive pressure sensor is formed by the three-dimensional elastomer itself. Experimental results demonstrate the outstanding performance of the DMESA approach. It offers simplicity in processing, the ability to adjust performance parameters, excellent spatial homogeneity, and the capability to differentiate varied inputs. Capacitive pressure sensors fabricated using this method exhibit high sensitivity and dynamic amplitude, making them promising candidates for various e-skin applications.

Conclusion

The DMESA method presents a highly promising solution for fabricating 3D microstructured elastomer layers for capacitive pressure sensors in e-skin technology. Its simplicity, performance adjustability, spatial homogeneity, and sensitivity to different inputs make it suitable for a wide range of electronic skin applications.

Cell-free fetal DNA (cffDNA) extraction from whole blood by using a fully automatic centrifugal microfluidic device based on displacement of magnetic silica beads

The purpose of this research was to design a fully automated centrifugal microfluidic system (Lab-on-a-Disk) for isolating cell free fetal DNAs (cffDNAs) from whole blood. To achieve this goal, magnetic silica beads were used, such that after attaching cffDNA to them, they were transferred between chambers by using external fixed magnets. All the standards and required steps for cffDNA extraction including plasma separation, adding proteinase K, lysis buffer, binding buffer, washing buffer, and elution buffer were considered in this designed disk. To evaluate the function of the disk, the collected samples were tested from several aspects. First, the purity of extracted plasma from whole blood was investigated which included hemoglobin test, hemocytometer, etc. This disk could extract 1.3 mL pure plasma from 3 mL blood with 45% hematocrit. The results of the extracted plasma showed 99% purity. Finally, the cffDNAs were examined by using a male fetal gender identification kit and real-time PCR machine. The results indicated the correct function of the disk in extracting cffDNAs in samples of 10 Landa from cycle 34 onwards. Compared to the clinical method, the disk not only was able to extract cffDNA in 20 min but also it led to less buffer consumption since the disk only required 1 mL plasma for extraction of cffDNAs.

An experimental study of centrifugal microfluidic platforms for magnetic-inertial separation of circulating tumor cells using contraction-expansion and zigzag arrays

Cancer diagnosis has recently been at the forefront of recent medical research, with ongoing efforts to develop devices and technologies for detecting cancer in patients. One promising approach for cancer diagnosis is the detection of Circulating Tumor Cells (CTCs) in blood samples. Separating these rare cells from the diverse background of blood cells and analyzing them can provide valuable insights into the disease's stage and lethality. Here we present the design and fabrication of a centrifugal microfluidic platform on a polymeric disk that utilizes centrifugal forces for cell isolation. The separation units exploit both active and passive methods. In other words, in addition to introducing novel geometry for channels, an external magnetic field is also employed to separate the target cells from the background cells. In order for the external field to function, the CTCs must first be labeled with antibody-conjugated nanoparticles; the separation process should be then performed. Before the experimental tests, a numerical study was done to determine the optimum parameters; the angular velocity and magnetization investigations showed that 2000 rpm and 868,000 (kA/m) are the optimum conditions for the designed device to reach the efficiency of 100% for both White Blood Cells (WBCs) and CTCs. These results indicate that the passive region of the channels primarily contributes to the focusing of the target cells, and showed that the focusing effect is more pronounced in the expansion-contraction geometry compared to the zigzag geometry. Additionally, the results proved that curved channel geometries performed better than straight ones in terms of separation efficiency. However, if the separation relies solely on channel geometry, the majority of cells would be directed towards the non-target chamber, leading to suboptimal results. This is due to the direction of the forces acting on the cells. However, including an external magnetic field improves the direction of the net force and enhances the separation efficiency. Finally, the numerical and experimental results of the study were compared, and the curved expansion-contraction channel is introduced as the best geometry having 100% and ∼92% CTC separation efficiency, respectively.

Numerical study of a double-stair-shaped dielectrophoresis channel for continuous on-chip cell separation and lysis using finite element method

Prognostication of numerous chronic diseases are in need of identifying circulating tumor cells (CTCs), afterwards, separating and reviving contaminated samples are required. Conventional methods of separating blood cells, namely cytometry or magnetically activated cell sorting, in many cases lose their functionality, or efficiency under different conditions. Hence microfluidic methods of separation have been implemented. Herein, an innovative integrated double stair-shaped microchannel is designed and optimized, capable of 'separation', and 'chemical lysis' simultaneously in which the lysis reagent concentration can be controlled to tune the lysis intensity. The method of insulator-based dielectrophoresis (iDEP), which is the main physics in this device, is utilized yielding maximum separation. Pivotal features of the applied voltage, the voltage difference, the angles and the number of stairs, and the width of the throat in the microchannel have been numerically explored in order to optimize the channel in terms of separation and the lysis buffer concentration. The overall state of optimum case for the voltage difference (ΔV) of 10 owns the following features: the number of stairs is 2, the angle of stairs is 110°, the width of throat is 140 μm, and the inlet voltages are 30 V and 40 V. Also, the overall state of optimum cases for delta possess the following features: the number of stairs is 2, the angle of stairs is 110°, the width of throat is 140 μm, and the inlet voltages are 30 V and 35 V.