Microfluidics and Nanofluidics最新文献

Liquid transport between parallel electrodes by electrowetting on dielectric (EWOD) is an effective method for microfluid manipulation in many applications. However, the mechanics of liquid motion are complex since many parameters and forces (i.e., electric force, surface tension force, contact line friction force, and viscous force) influence the liquid motion. In this study, we present a new electromechanical model to analyse the transient dnamics of liquid motion. Three common liquids (NaCl and KCl solutions: 3*10^− 4 S/m and DI water: 1.5*10^− 3 S/m) are used to verify our model at three frequencies (i.e., 1 kHz, 10 kHz and 100 kHz). Compared to previous studies, there are three novel features of this study: (1) the absolute value of complex permittivity was added into the model to clarify conductivity-dependent and frequency-dependent liquid motion; (2) the conductivity-dependent and frequency-dependent transient dynamics of liquid motion were investigated; and (3) four conductivity-dependent and frequency-dependent forces were investigated. In the model, the electric force and surface tension force are constant during the full process of liquid motion. The liquid moves slowly with time since the viscous force increases with time. In addition, NaCl and KCl solutions also showed similar behaviour since their conductivities and other experimental conditions are the same. In this work, the experimental data showed good agreement with theoretical predictions. Our model can successfully clarify the conductivity-dependent and frequency-dependent transient behaviour of liquid motion. The developed model can be used to predict the dynamics of fluids in parallel-plate microfluidic devices for many applications.

Therapeutic drug monitoring (TDM) is essential for giving patients a prompt and precise dosage to increase effectiveness and reduce toxicity. The study of TDM is crucial at present due to their widespread use for both legal and illegal medical purposes. Many researchers in various studies have used nanomaterials for drug detection in general, but few have used this technique for detecting drugs. Here, a 3D-printed microfluidic device with a novel design is presented for the detection of narcotic drugs in blood plasma samples. Various diagnostic measurements, such as UV, XRD, FESEM, TEM, FT-IR, and zeta potential, were conducted to characterize the synthetic nanoparticles. The study indicated that the best elements used in the detection of narcotic drugs are silver, cobalt, and copper-nickel bimetallic particles. The device is portable and simple to use, and the method that was demonstrated good linearities (R2 > 0.98). The relative standard deviation (RSD%) was less than 10% (n = 3), suggesting high precision, and the limit of detection (LOD) values for fentanyl citrate, tramadol hydrochloride, and pethidine hydrochloride were estimated to be0.143 mg/L, 0.241 mg/L, and 0.347 mg/L, respectively, and the limit of quantification (LOQ) was 0.584 mg/L, 0.748 mg/L, and 0.946 mg/L, respectively. This low-cost, point-of-care (POC) approach may improve patient and physician convenience, make treatments safer, and expand the availability of TDM in various locations.

Because temperature is one of the environmental factors that can influence chemical kinetics and fluid properties, there is a need for microfluidic devices that can control the temperature uniformity of the reaction zone to minimize errors in the analysis. A novel microfluidic device design leveraging the spatial freedom enabled through stereolithographic (SLA) 3D printing is presented. Building on advances in high resolution fabrication, a microfluidic device was created that can heat a sample volume of 5 (mu L) between 30-90(^circ C) with a spatial temperature variation of 0.3(^circ C) or less. To achieve this level of spatial uniformity, the design incorporates removable support structures, channels for liquid metal loading to act as heating elements, and a central suspended hexagonal segment to provide thermal isolation from external connections and multi-axis heating. This device also features complete internal optical access for fluorescence-based measurements. Optimization of the temperatures within the device was performed using COMSOL multi-physics and validated against experimental measurements. The applicability and limitations of this device for DNA analysis are discussed, particularly the observed interactions between the PEGDA device and water or oil-based solutions at sustained higher temperatures.

An early study on the biological consequences of using polydimethysiloxane (PDMS) for microfluidic cell culture reported that estrogens could be sequestered by PDMS; however, the PDMS interaction parameters of specific hormones have not been reported. Without these parameters, it is not possible to assess whether such sequestration is a problem for a particular device and flow rate combination. Here we quantify chemical-PDMS interactions for a commonly used estrogen and two additional steroid-class hormones: estradiol, aldosterone, and progesterone. We find that aldosterone does not detectably interact with PDMS; estradiol interacts modestly; and progesterone interacts strongly. Based on these measured interactions, we computationally model dynamic dosing protocols based on pulsed/bolus delivery and circadian control. We show that interactions with PDMS can strongly disrupt these dynamic dosing protocols in a chemical-specific and flow-rate-dependent manner. Notably, estradiol-PDMS interactions can have significant impacts under static conditions or low flow rates, but those impacts become negligible at higher flow rates. These results have critical implications for the use of steroid hormones in PDMS-based microfluidic devices.

This study analyzes the dynamics and stability of an outer thin-walled shell with micro-dimensions, which conveys a swirling fluid in the annular zone between the inner and outer shells. Based on the modified couple stress theory and Donnell shell theory, the motion control equations for the shell are derived through Hamilton’s principle. Fluid force is determined by using the potential flow theory that combines no-slip and slip boundary conditions. The objective is to discover the influences of the fluid rotation, geometry parameters and the Knudsen number on the stability of the micro-scale shell. The instability mechanism of the system caused by different fluid forces is discussed. In addition, the Knudsen number can reduce the critical flow velocity and make the dimensionless phase velocity in the annulus faster.

The study investigates the design, fabrication, and testing of an advanced microfluidic system for precision soil nutrition detection. It presents an interpretable AI (IAI) as a hybrid approach combining MHBACN_LIME-MSHO to optimize microfluidic systems for enhanced soil nutrient detection. RSM is used to model the relationship between the factors such, as Reynolds number, reagent concentration, applied pressure, and velocity, and the responses include flow rate, mixing index, effective mixing length, and nutrient density. The analysis of RSM models shows high explanatory power with strong R² values exceeding 0.9, indicating a reliable predictive model. A desirability value of 0.972 indicates that the optimal solution. The IAI demonstrates superior performance when compared to traditional methods such as DNN-BA and DT-GWO. The proposed microfluidic chip was validated using real soil samples, demonstrating accurate NPK detection under practical conditions. The results from error analysis, including MSE (0.007), highlight the robustness and precision of the proposed model. The proposed IAI framework not only optimizes system parameters but also provides interpretability, making it a valuable tool for real-world applications. This work offers a comprehensive, reliable, and optimized solution for microfluidic systems.

The hydrodynamic characteristics of liquid-liquid flows in a micro-mixing plate with a ‘heart/spade’ geometry and a hydraulic diameter of (sim) 0.36 mm at the contraction point are studied experimentally in the Reynolds number range of (250 - 1,000). Localised optical observations of the two-phase flow within the micro-mixing device units are performed using a high-speed camera in combination with an LED-induced fluorescence imaging technique. A qualitative interpretation of the instantaneous images enabled the development of a regime map with three stable flow patterns, each with a metastable transitional state. The formation of secondary flows and recirculation zones resulted in the breakup of interfaces and fragmentation of droplets. The droplet size distribution of an MTBE-water dispersion is studied across a broad range of the dispersed phase (water) ratios, (phi _{textrm{d}} = 0.091 - 0.714). The resulting Sauter mean diameter of water droplets is used to evaluate the improvement in the specific surface area and was correlated as a function of the energy dissipation rate and the Reynolds and Weber numbers.

This article investigates the convective instability of a micropolar fluid-saturated horizontal porous layer. An inclined temperature gradient along with the horizontal throughflow is considered during this investigation. The primary aim of this article is to explore the nature of the micropolar fluid parameters on the transverse and longitudinal rolls in the presence of horizontal throughflow. The following parameters, such as coupling number, micropolar parameter, Darcy number, porosity of the medium, horizontal Rayleigh number, and Péclet number, mainly control the flow. The base flow is a combination of horizontally moving mass flow and flow induced by an inclined temperature gradient. This particular flow configuration is known as the Hedley-Prats flow. The eigenvalue problems related to the transverse and longitudinal rolls are numerically solved using the bvp4c routine in MATLAB. A comparison of the numerical results for the Darcy number on the Hadley–Prats flow in the Brinkman model with those of the current problem reveals a high degree of concurrence. It is observed that the direction of the horizontal throughflow does not significantly affect the stability region of micropolar fluids under an inclined temperature gradient. Furthermore, the presence of micropolar fluid parameters (such as (N_text {1}) and m) always stabilizes the flow characteristics.

Droplet dynamics is a critical area of study with significant implications across various fields, including industrial processes and biological systems. This paper presents a novel methodology—Machine Learning-Enhanced Computational Fluid Dynamics (ML-CFD)—to predict energy dissipation mechanisms in droplet dynamics and their effects on wetting phenomena. We analyze primary energy dissipation mechanisms—viscous, interfacial, and thermal—and discuss their roles in influencing dynamic wetting behaviors, contact angle hysteresis, and droplet stability on solid surfaces. By examining relevant equations and models, we elucidate how viscous, interfacial, and thermal dissipation mechanisms collectively influence wetting characteristics. The findings underscore the importance of understanding energy dissipation in optimizing applications across microfluidics, material science, and surface engineering, ultimately enhancing predictive capabilities and informing the design of advanced materials and systems.

The splitting modes of droplet flow in bifurcated minichannel networks are valuable for distributing them in various microfluidics chemical applications and have been widely studied. Previously, predictions of the splitting modes relied on the models of hydraulic flow resistance. This paper presents an experimental study on the correlation between droplet splitting modes and droplet travelling speed characteristics in various minichannel networks. A high-speed camera and machine vision algorithm were used to measure the instantaneous travelling speed of droplets at the inlet and arms of the networks. Five typical splitting modes are identified: bypass splitting, breakup splitting, random splitting, uniform splitting and oscillating splitting. The characteristics of the droplet speed corresponding to different splitting modes are studied and understood by analyzing their varying features and correlations. The results show that splitting modes can be correlated to droplet travelling speed characteristics. This research focuses on how to identify and monitor droplet splitting modes at T-junctions, which relies solely on local visual features of several droplets. It lays the foundation for regulating different splitting modes in the future.