Microfluidics and Nanofluidics最新文献

Microfluidic technology is designed for the liquid handling and manipulation of fluids and materials at a small scale. This technology offers distinct advantages that address the limitations of conventional methods such as precision control, reproducibility, efficiency, and rapid processing. These advantages signify a paradigm shift in the field of biomedical and pharmaceutical research, particularly in the preparation of nanomedicines. This review briefly introduces microfluidics along with its principles and fundamentals, including the key components, different types of microfluidic mixing mechanisms, and materials used in microfluidic devices. It also comprises a detailed discussion of the benefits and challenges of using microfluidics in preparing nanoformulations (such as lipid-based, polymer-based, inorganic-based, and hybrid-based) and biomedical applications. This review also discusses the advancement of microfluidic and nanomedicine preparation, such as modular microfluidics, digital microfluidics, three-dimensional (3D) printed chips, automated microfluidics, artificial intelligence (AI), and healthcare wearable devices (HWDs). The review concludes by encouraging cooperation between multiple parties for the success of nanomedicine and offering better patient care to the public.

Efficient mixing of fluid streams in microfluidic devices remains a critical challenge due to the dominance of laminar flow, where mixing relies solely on diffusion. To overcome this limitation, various microfluidic mixers have been developed to transition from laminar to non-laminar regimes, enabling faster mixing rates. Passive micromixers utilize geometric channel designs instead of external energy sources, making them advantageous due to their simplicity. Among these, convergent-divergent micromixers employ alternating narrow and wide channels to stretch and fold fluid streams, enhancing the mixing process. This study explores a novel series of microfluidic mixers based on dynamical-billiard-shaped chambers. Each microfluidic mixer comprises twenty consecutive nanoliter billiard-shaped chambers connected by relatively narrow channels of equal or variable lengths. Six chamber designs were analyzed: three chaotic billiard shapes (Bunimovich-stadium, diamond-shape, and Sinai-billiard) and their respective non-chaotic counterparts (ellipse, triangle, and ring). Two spatial arrangements—out-of-axis and on-axis chambers—were tested to evaluate their impact on mixing efficiency. Key findings reveal that an out-of-axis chamber configuration significantly enhances mixing, as does connectors with varying lengths. Orientation of the initial chamber at a 36° angle further improves performance. However, chaotic chambers did not consistently outperform non-chaotic ones, likely due to limitations in flow rates. Comparisons with a previously reported baffled structure, considered an excellent micromixer, showed improved mixing efficiency using both chaotic and non-chaotic chambers. These results provide valuable insights into passive mixing mechanisms, contributing to the design of more efficient microfluidic mixers adaptable to specific experimental conditions.

The development of drug resistance in breast cancer cells posed significant challenges that necessitate overcoming. Traditional two-dimensional cell research models failed to replicate the tumor microenvironment (TME) in vivo, thus necessitating the utilization of three-dimensional cell culture models for anti-cancer drug research. In this study, we utilized a matrix-free microfluidic three-dimensional (3D) biomimetic chip to generate uniformly sized and highly viable tumor cell spheroids, setting it apart from conventional matrix-based spheroid models. Simultaneously, these cell spheroids were accurately retrieved and embedded within type I collagen to establish the TME environment and further investigate the mechanism by which type I collagen influences doxorubicin resistance in breast cancer cells. The research findings demonstrated that type I collagen enhanced the doxorubicin resistance in breast cancer cells by upregulating the expression levels of Bcl-2, Bcl-XL, and MRP1 proteins. Additionally, the up-regulation of MRP1 is mediated through the ERK1/2 signaling pathway. In conclusion, we posited that this microfluidic biomimetic chip offered a novel and sophisticated platform for three-dimensional tumor research. This platform was expected to facilitate a more comprehensive elucidation of the pharmacokinetic properties of tumor cells within the extracellular matrix (ECM) in future studies, thereby enhancing the efficiency and accuracy of in vitro drug screening.

Identifying blood type is a routine procedure for blood transfusion, typically performed using forward and reverse typing methods. However, distinguishing blood subtypes remains a challenging task in clinical practice. This study proposes a novel approach to rapidly differentiate blood subtypes based on the distinct binding strengths between red blood cells (RBCs) and antibodies immobilized on a micro-channel surface. Different blood subtypes can be distinguished by measuring the ratio of RBCs before and after applying a shear force with a wash buffer. Experimental results demonstrate residual ratios of approximately 99.5%, 31.8–39.8%, 7.4–7.6%, and 10.0–11.1% for B, B₃ (including AB₃), B_el, and A_el types, respectively. Notably, this method makes it possible to differentiate subtypes with minimal surface antigens, such as B_el and A_el, within 15 min—significantly faster and less complex than the conventional adsorption–elution method used in clinical settings. This proposed approach offers a promising solution for rapidly differentiating rare blood subtypes.

We present a cleanroom-compatible fabrication route to open space microfluidic devices, utilizing a multilayer lamination/photolithography process on the wafer scale. The devices were applied to generate and maintain molecular surfactant films. In a dedicated setup, film stability was investigated in conjunction with 108 kHz ultrasonic sound, and response to acoustic waves in the audible range was determined.

A novel on-chip inductive detection sensor has been developed, offering a new method for analyzing contaminants and viscosity in hydraulic oil. An ultra-high-throughput microchannel with a rectangular cross-section has been designed, along with a dual-core coil resonant method to generate a large-scale magnetic field with high sensitivity on the chip. The inductive sensing unit consists of two symmetrically arranged rectangular magnetic core coils, creating a detection area with a high magnetic field strength. A rectangular microchannel with a cross-sectional area of up to 6 mm² passes between the two magnetic core coils. Compared to traditional micro-inductive sensors, the throughput increased by nearly 2 orders of magnitude, reaching 120 mL/h. Using the microchannel and resonance measurement method, we successfully detected 30 μm iron particles and 80 μm copper particles. Furthermore, we have established a model that correlates oil viscosity with its transit time through the microchannel. Through the inductance signal, we can determine the time it takes for the oil to pass through the coils and subsequently calculate its viscosity using our theoretical model. This method allows for the integration of inductive detection and viscosity measurement without the need for additional sensor. In the experiment, we measured hydraulic oils of different viscosities and compared the results with measurements obtained using a viscometer to verify the accuracy of the viscosity measurements.

Glucose monitoring is critical for diabetes management, yet traditional invasive methods remain fraught with discomfort and logistical challenges. Recent advancements in microwave-based microstrip line sensors offer a transformative alternative, leveraging electromagnetic interactions with biological tissues to detect glucose-induced dielectric changes non-invasively. This review examines the evolution of microstrip line-based sensors, emphasizing their design principles, operational mechanisms, and clinical applicability. Current challenges, such as environmental interference, tissue heterogeneity, and signal stability, hinder widespread adoption. Among the diverse technologies evaluated, resonator-based sensors, particularly split-ring (SRR) and swastika-shaped geometries that demonstrate superior performance due to their multi-parameter sensing capabilities, high sensitivity (e.g., 148.367 Ω/(mg/mL)), and compact design. These sensors integrate reflection coefficient phase, magnitude, and impedance measurements, enhancing robustness against noise and biological variability. While metamaterial and implantable antennas show promise, their limitations in scalability or biocompatibility underscore the practicality of resonator-based systems. Future efforts must prioritize clinical validation and integration with machine learning to address individual variability. In conclusion, resonator-based microstrip sensors represent the most viable path toward reliable, continuous glucose monitoring, combining innovation with practicality to redefine diabetes care.

In this manuscript, heat transfer and flow characteristics (HTFC) of multi-walled carbon nanotubes (MWCNT)/water nanofluids investigated in flat and circular tubes under constant heat flux (CHF) conditions, experimentally. The two-step method was used in preparing nanofluids at various weight fractions of 0.01, 0.05, 0.1 and 0.3 wt.% with the use of cetyl trimethyl ammonium bromide (CTAB) surfactant. The thermo-physical properties (TPP) such as thermal conductivity (TC) and viscosity were studied through instruments. Specific heat and density were calculated through standard theoretical equations. TC enhanced with temperature and particle concentration. The experiments were performed in test rig having both flat and circular tubes connected in parallel. Fluids were flow through tubes at different flow rates 0.15–0.5 L/min. Thermal performance was measured through two parameters such as heat transfer coefficient (HTC) and Nusselt number. Both parameters were increased with increase in nanoparticle concentration and flow rate of nanofluids. Highest enhancement in HTC of 0.3 wt.% nanofluid was 72.13% and 82.82% at flow rate 0.5 L/min compared to that of distilled water in circular and flat tubes, respectively. HTC enhancement of 17% was obtained in flat tube compared to circular tube at similar operating conditions. Pressure drop (PD) for 0.3 wt.% nanofluid was 2.35 times and 2.63 times at 0.5 L/min flow rate in circular and flat tubes, respectively. Energy efficiency ratio ((eta)) was also calculated to be 1.57 and 1.39 for 0.3 wt.% and 0.5 L/min for flat and circular tubes, respectively. Flat tube showed good thermo-hydraulic performance compared to circular tube under similar operating conditions.

In this study, we propose and develop an autonomous picoliter droplet array-generating device using a centrifugal microfluidic system. Droplet arrays play a crucial role in the advancement of chemical analyses, such as digital quantification and digital PCR. In digital quantification, it is important to standardize the size of the droplets and ensure the ease of analysis of the detection reactions within each droplet. Hence, we developed a device that can form droplets of a predetermined size within pre-arranged cup structures simply by flowing liquid and successfully controlled the flow for generating picoliter droplet arrays. The flow control was conducted simply by rotation, and it was not necessary to customize the centrifuge. By optimizing the cup arrangement and these spaces, the device realized that approximately140 pL of highly uniform droplets with an area concentration as high as 32 pieces per square millimeter. Moreover, by implementing an evaporation-prevention function, it was confirmed that the droplets could be retained for more than 30 min. Owing to its simplicity, it is expected to make a significant contribution to the widespread adoption of digital quantification and advancement of analysis.

The present investigation considers roughness elements which are generally very small relative to the principal flow length scale, and about the same order of magnitude as the molecular mean free path of helium. Significantly different rarefaction flow behavior is produced using three roughness arrangements, which have different character and structure in regard to distributions of larger ridges, as well as sizes, shapes, and distributions of smaller roughness elements. Measured distributions of slip velocity and associated tangential momentum accommodation coefficients are provided as they vary with Knudsen number Kn, disk rotation speed ω, and mean roughness height Ra. Results are given for helium and air as working fluids, three different surface roughness types, different disk rotational speeds ω, different volumetric flow rates, and different flow passage heights h. Knudsen number values range from 5.21 × 10^–3 to 2.15 × 10^–2 for helium, and from 1.82 × 10^–3 to 7.53 × 10^–3 for air. The device employed to produce these data is a viscous disk pump (VDP). With smallest mean roughness height, all of the elements on the surface are about the same size, which is about the same as the molecular mean free path of helium, and a larger percentage of molecules are subject to specular reflection resulting in substantial slip velocity magnitudes. With largest mean roughness height, a diversity of roughness element sizes, shapes, and heights is present, and a larger percentage of molecules are subject to diffuse reflection resulting in relatively small slip velocity magnitudes.