Microfluidics and Nanofluidics最新文献

In this work, the combined impacts of electroosmosis and peristaltic processes are investigated to better understand the behavior of fluid flow in a symmetric channel. The Poisson–Boltzmann equation is included into the Navier–Stokes equations to account for the electrokinetic effects in micropolar fluid model. The fluid motion caused by electric fields is effectively described by incorporating electrokinetic variables in these equations. Under the premise of a low Reynolds number and small amplitude, the linearized equations are resolved. Partial differential equations are solved to yield analytical formulations for the velocity and pressure fields. As opposed to earlier research, our analysis explores the combined impacts of electroosmosis and peristaltic motion in symmetric channels. By considering these mechanisms together, we gain a comprehensive understanding of fluid movement and manipulation in microchannels. According to research on modifying the properties of fluid flow, zeta potential, applied voltage, and channel shape all affect the velocity of electroosmotic flow. In addition, the flow rate is impacted by the peristaltic motion-induced periodic pressure changes. In addition, the combined effects of peristalsis and electroosmosis show promise for accurate and efficient regulation of fluid flow in microchannels. The study reveals that the micropolar parameter modifications (0–100) have little effect whereas adjusting the coupling parameter (0–1) modifies electroosmotic peristaltic flow. Center streamlines are trapped and then aligned in a length-dependent way by the interaction of electric fields. Several microfluidic applications, including mixing, pumping, and particle manipulation, are affected by the findings of this research. The electroosmosis and peristaltic processes may be understood and used to create sophisticated microfluidic devices and lab-on-a-chip systems. This development has the potential to greatly improve performance and functionality in industries like chemical analysis, biomedical engineering, and other areas needing precise fluid control at the microscale.

The electro-osmotic flow (EOF) in a neutral system consisting of an aqueous NaCl solution confined in a nanochannel with two parallel Molybdenum disulfide ((text {MoS}_{text {2}})) walls and in the presence of an external electric field parallel to the channel walls, is investigated for the first time. The results indicate that the thickness of the Stern layer grows as the negative electric surface charge density on the nanochannel walls increases. The Stern layer becomes thinner as the salt concentration is increased. Moreover, the EOF occurs under the no-slip condition on the walls. In addition, by increasing the surface charge density the average of the flow velocity across the nanochannel initially grows (Debye–Hückel regime) and reaches its maximum value. Then, by further increasing the surface charge density the water flow rate decreases (intermediate regime), and gets the zero value and becomes negative (reverse flow regime) at even larger values of the surface charge densities. Comparing the results of the previous work wherein the channels are composed of the black phosphorene walls with those of the present study for a channel composed of (text {MoS}_{text {2}}) surfaces, show that for the latter case the reverse flow occurs at a lower surface charge density and with a greater value of the peak velocity with respect to the change in the surface charge density for the former case.

Mathematical and computational models linking cell mechanical properties with deformation are crucial for understanding cellular behavior. While various techniques measure the stiffness and viscosity of cells, recent experiments suggest that cells exhibit poroelastic behavior, characterized by solid mesh networks immersed in cytosol liquid (Moeendarbary et al. in Nat Mater 12:253–261, 2013. https://doi.org/10.1038/nmat3517). Despite this, a mathematical model relating poroelastic cell deformation and Young's modulus of solid networks has not been reported. This study presents the first poroelasticity-based mathematical model for relating cell deformation with Young’s modulus of solid mesh networks. The model is validated by utilizing the experimental data of the cell’s squeezing behavior through a constriction microchannel. The predicted Young’s modulus for HeLa, MCF-10A, and MDA MB-231 cell lines are 153.64 ± 60.3 kPa, 97.84 ± 41.7 kPa, and 67.9 ± 48.8 kPa, respectively, which matches well with the conventional measurements. Additionally, two artificial neural network (ANN) models were developed which predicted Young's modulus and viscosity for these cell lines based on migration and deformation characteristics through constriction microchannel, achieving high accuracy (R ~ 0.974 and R ~ 0.999, respectively). Further, a linear Support Vector Machine (SVM) model classified cell lines based on initial diameter and elongation in the constriction microchannel measured from static images. The combined analytical and computational approach proposed here offers direct quantitative estimates of cell mechanical properties and cell classification based on their squeezing behavior through constriction microchannel.

The uniformity of the deposition in the plasma-enhanced chemical vapor deposition (PECVD) process is greatly influenced by the uniform effect of the microchannels in the showerhead. Most of the previous studies on showerheads have primarily focused on the axial-direction of microchannels. However, there is a lack of comparative studies on the influence of radial changes and different flow regimes on the flow characteristics of microchannels. In this paper, we utilized the coupling of the Navier–Stokes and Direct Simulation Monte Carlo (NS-DSMC) methods to compare the differences between expansion type microchannels and equal-diameter type microchannels in the slip and transition regimes. The results indicate that in the slip flow regime, the microchannel of equal diameter exhibits a stronger jet compared to the expansion type. However, this situation reverses as the slip flow regime transitions to the transition regime. This reflects the influence of the flow regime on the characteristics of the microchannel and the potential of the combined type to enhance deposition uniformity.

The migration of sperm cells in a female reproductive tract is responsible for the successful fertilization of the female egg. In this research work, the effect of the surrounding fluids on the motion of sperm cells has been studied using a microfluidic channel. To analyze the motility of sperm, primary motility parameters such as velocity, beat frequency, amplitude, and derived parameters such as linearity, straightness, and wobble have been measured. The results indicate that sperms possess higher progressive motility in non-Newtonian fluids compared to Newtonian fluids in the same viscosity range. The motion of the sperm shows an inverse relationship between the amplitude of the head trajectory and the beat frequency of the flagella. Numerical studies were performed to measure the drag force on these sperm. The trajectories of the flagella, forces acting on sperm, power generated, pulling power, and efficiency of the sperm motion through the fluid medium have been investigated and a relationship between the force and rotation of the flagella has been established. The results show that the flagella also change their shape based on the properties of the surrounding fluid. This study aims to improve our understanding of issues related to infertility diagnosis and help design in-vitro experiments required for sperm separation.

The separation of cancer cells from blood samples is one of the most crucial tasks in cancer research. However, existing methods tend to be expensive and labor intensive. Accordingly, the present study proposes a low-cost platform that uses hydrodynamic effects for the label-free separation of cancer cells from whole blood samples using a simple centrifugal microfluidic device consisting of a Y-shaped microchannel, a contraction–expansion array (CEA) microchannel, and a bifurcation region. To enhance the separation efficiency, the input branches of the Y-shaped microchannel are designed with different widths to generate a sheath flow rate greater than the sample flow rate. As the sample flows through the CEA microchannel, the cancer cells are separated from the blood cells through inertial effects and the bifurcation law. Finally, the cancer cells are collected from the low-flow-rate branch of the bifurcation region. The feasibility of the device is first demonstrated by numerical simulations. Experimental trials are then performed to separate K562 cancer cells from blood samples with various hematocrit concentrations at disk rotational speeds ranging from 1000 to 3000 rpm. The experimental results show that the cancer cells can be successfully separated from a diluted blood sample with a ratio of 1:1.2 × 10⁵ K562 cells to blood cells with a high efficiency of 90% at an angular velocity of 2000 rpm.

This study proposed a two-step simple method for rapid superhydrophobic surface modification of PDMS for PDMS-based microfluidics. A laser-patterned PMMA plate was used as the mask for the following selective CO₂ laser surface treatment on PDMS. The water contact angle, SEM and ATR-FTIR analysis were conducted for the characterization of the proposed superhydrophobic surface modification method for PDMS. The result shows that the water contact angle on the modified PDMS surface reaches around 160° with the laser power of 12 W and with a scanning speed of 60 mm/s. This method aims to develop a faster, easier, and low-cost method for selective superhydrophobic modification method for PDMS-based microfluidic devices. The proposed method could have wide applications potentials in the microfluidics field, especially for PDMS-based droplet microfluidics.

This study proposes a novel co-flow capillary microfluidic device that can generate highly monodisperse droplets and polymeric microspheres. The device mainly consists of two self-aligning special-shaped polymeric capillaries. The outer capillary features a gradually contracting and expanding geometry, and the inner has an elliptical cross section at the end. The elliptical nozzle of the inner capillary fits into the contraction region of the outer capillary, and so assembled device, namely a plane-symmetric co-flow capillary, benefits from the self-alignment of the capillaries. The design and manufacturing process of the device are outlined, including a discussion on how the processing conditions affect the capillary geometry. Subsequently, the proposed device is used for droplet generation tests, and the diameter distribution of generated droplets and their influencing factors are investigated. The droplet generation mechanism with the elliptical nozzle is discussed with the help of modeling and simulation. Furthermore, monodisperse porous polymeric microspheres are fabricated using the proposed device, and their porous features are characterized. The results show that the proposed device can produce monodisperse droplets with a mean diameter of a few hundred micrometers and a coefficient of variance (CV) of less than 1%, reflecting the stability of the device. Additionally, porous polymeric microspheres could be successfully produced, and the CV of the size distribution is only around 1%.

The Controlled transport of tiny particles in a microfluidic environment has attracted the attention of numerous researchers in the field of lab-on-a-chip. In this work, for the first time, a fully operational microfluidic chip composed of asymmetric magnetic tracks that unidirectionally transport multiple magnetic particles synced with a general tri-axial magnetic field is proposed. In this innovative chip, the particle motion is analogous to the electron transport in electrical diodes, with similar controllability and automation levels not seen in other single-particle manipulation systems. The vertical bias component of the magnetic field by providing a repulsive force between the particles and preventing undesired cluster formation, makes the proposed chip even more similar to the electrical circuits. Additionally, the chip functions as a highly sensitive biosensor capable of detecting extremely low levels of DNA fragments using ligand-functionalized magnetic beads. The uniqueness of the proposed sensor lies in the introduction of a novel particle/analyte concentrator based on the proposed diodes, which enhances its detection sensitivity. This sensitivity is even further enhanced by a single-particle and pair detection image processing code. Furthermore, the background noise is reduced by eliminating the unwanted bead cluster formation commonly observed in previous works. The proposed device serves as a high-throughput unidirectional transport system at the single-particle resolution, offering sensitive bio-detection with many applications in biomedicine.