Microfluidics and Nanofluidics最新文献

One of the key technologies for developing materials science, microfabrication, and biomedical engineering is the manipulation of microparticles in microfluidic systems. Among the five main manipulation techniques, mechanical, electrical, magnetic, optical, and acoustic, acoustic manipulation has shown great promise because of its special benefits, which include label-free operation, biocompatibility, and efficiency in optically opaque surroundings. With an emphasis on surface acoustic waves (SAWs), bulk acoustic waves (BAWs), acoustic holography, and hybrid acoustic-optical platforms, this paper thoroughly investigates current advancements in acoustic manipulation techniques. In addition to outlining the governing equations and recent advancements in the field, this review paper addresses the key challenges, identifies research gaps, and explores future directions.

Among other things, sweat is the ultrafiltrate of blood plasma, an essential physiological fluid in the human body. It harbours a wide range of metabolites, electrolytes, and other biologically relevant markers that are directly correlated with human health. Relative to other body fluids e.g. blood, tears, interstitial fluid and saliva, sweat has specific benefits of ease of collection and detection that is non-invasive. During recent years, much focus was put on wearable sweat sensors because of their possibility to provide permanent monitoring of biomarkers. The use of wearable bioelectronics has attracted great attention even in the world of medicine due to its vast potential of predictive medical modelling and the ability to conduct personalised Point of Care Testing (POCT). These devices have many attractive features which include lightweight, flexible, great stretchability, and low price. In situ analysis of sweat biomarkers through electrochemical methods has been extensively used as widely reviewed by different researchers. The aim of this paper is to present a literature review of the latest advancements in non-invasive, continuous glucose monitoring with sweat sensors. It will point out various strategies and devices, which can be used in wearable platforms. This review provides insight knowledge that is essential in carrying out effective critical analysis of current problems. In it, wearable glucose biosensors have been classified based on the methodology, and the challenges of each specific approach have been discussed.

Microfluidics is pivotal in producing monodisperse microemulsions and microspheres. However, lower output efficiency hinders its practical application. Although multichannel droplet generators offer a promising solution for increased productivity, their design is inherently complex, and achieving uniform fluid distribution across channels is a significant challenge. Hence, in this paper, a novel rapid-design approach is introduced for multichannel droplet generators and employs topology optimization to enhance the structure, leading to significant improvements in droplet generation efficiency and uniformity. It can automatically generate a multichannel droplet generator structure that meets experimental conditions within five hours and is compatible with 3D printing technology. By employing topology optimization, the design achieves an average inter-channel flow rate variation of less than 1%, even with 81 channels, while reducing the inlet-outlet pressure drop by 19.75% compared to unoptimized configurations. The optimized device can produce both water-in-oil (W/O) and oil-in-water (O/W) droplets at a maximum throughput of 65 mL·min⁻¹, with a coefficient of variation (CV) below 5%, ensuring excellent monodispersity. Moreover, the topology optimization approach provides a comprehensive analytical framework for droplet generators with a matrix of microchannels, thereby facilitating rational design and scalability.

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The biochip is a solid, miniature substrate that may accommodate several test locations, allowing for concurrent biochemical investigations and reactions. In essence, it is a “miniaturized laboratory” or “microarray” where certain bio-molecules are immobilized on a surface. Over the past few decades, Continuous-Flow Microfluidic Biochips (CFMB) has been widely used to automate lab processes in molecular biology and biochemistry. In the recent years the lab automation in the field of molecular biology and biochemistry has been progressed through the development of Digital Microfluidic Biochips (DMFBs). DMFB was rapidly used during 2019 coronavirus disease pandemic (COVID-19). In critical diseases identification, the volume of the reagent or the samples play important role. The major challenges in the DMFB technology such as fixed electrode structure, variable sample or reagent size, non availability of in-process error recovery, limited sensor integration and high cost of production makes the conventional DMFB biochips less popular now a days. To circumvent the associated problems with DMFBs, the researchers came up with new solution is the field of microfluidic biochips is called Micro-Electrode-Dot-Array (MEDA)-based biochips. In this work a comprehensive review of the studies has been made regarding architecture, sample preparation, routing algorithm and synthesis of three different kinds of microfluidic biochip technologies. To begin the review, 327 research papers were chosen from the different academic databases within a span of 55 years starting from 1971. After deploying comprehensive screening process, this review considered 188 studies based on the relevance and importance. The different methodologies, benefits, and shortcomings of microfluidic biochip technologies have been lucidly elaborated in this paper which will be beneficial for biochip researchers.

A microbalance that uses a microchannel resonator requires several samples to perform high-sensitivity measurements. However, multiple procedures are required to embed the resonator’s microchannels, which results in high fabrication costs. In this study, we establish a high-sensitivity mass measurement method based on the eigenmode shift in virtually-coupled stainless steel microchannel resonators. We use a pin-shaped electrode to excite the microchannel resonators via electrostatic force. The microresonator does not require semiconductor-specific fabrication equipment because we use a combination of metal etching and diffusion bonding to bury the channels. We combine this approach with the use of a virtually-coupled resonator with dynamics calculated in a computer and verify its effectiveness as a small mass measurement method. Self-excitation of the weakly coupled resonators induced by nonlinear feedback control compensates for increments in viscosity through corresponding increments in the internal viscosity. We measure the densities of distilled water, ethanol, and saline water to compare the sensitivities of methods using eigenfrequency and eigenmode shifts. Use of virtual coupling realizes eigenmode shifts that are two orders of magnitude higher than the corresponding eigenfrequency shifts.

In this study, we developed novel microwave microfluidics that enable the parallel heating of two microchannels at different temperatures within a single post-wall waveguide to accelerate the search for optimal temperature conditions in combinatorial synthesis. The proposed structure consists of two transversely arranged microchannels embedded in a post-wall waveguide whose sidewalls are formed by metal posts. This enables both single-mode microwave propagation and suppression of microwave leakage. A temperature gradient is established between the two channels by exploiting the difference in the microwave absorption between the upstream (CH-A) and downstream (CH-B) channel solvents. Water temperature measurements in each channel under a 3.0 W microwave input demonstrate a steady-state temperature of 82.8 ± 1.6 °C in CH-A and 72.1 ± 0.7 °C in CH-B, confirming the formation of a 10 °C temperature difference. Furthermore, the on-chip synthesis of 4-phenyltoluene, a pharmaceutical intermediate, was conducted via Suzuki–Miyaura coupling using this heating structure, and the product yield was quantified by gas chromatography. The reaction yield depends on the microwave input power and reaction time, with CH-A consistently yielding a higher product conversion than CH-B. These results demonstrate that the proposed device enables the formation of a temperature gradient and parallel synthesis under different thermal conditions within a single waveguide. This suggests that the device is an effective heating platform for combinatorial synthesis, offering a high-density selective temperature control. Accordingly, this structure is expected to contribute to the rapid optimization of reaction conditions for pharmaceutical and material development.

The limitations of traditional, animal-model-based preclinical drug testing methodologies have contributed to an extremely high failure rate of new drug candidates in various phases of clinical trials. Organ-on-chip (OoC) technology has emerged as a promising alternative, providing a physiologically relevant microenvironment for drug testing. However, challenges such as high costs, inadequate physiological replication, and particularly the lack of standardized validation approaches have undermined the widespread adoption of OoCs. Additionally, the need for in silico-assisted functional verification to accelerate drug development, reduce investigational expenses, and enhance ethical feasibility has been increasingly experienced by researchers. In this study, we developed and validated a microfluidic skin-on-chip (SoC) platform that supports dynamic skin co-culture for 11 days. The model was characterized by using live-dead cell staining, fluorescent cell tracking, hematoxylin and eosin (H&E) staining, and immune-histochemistry analysis. In vitro drug diffusion studies with caffeine and salicylic acid were performed and quantified using high-performance liquid chromatography. To enhance predictive accuracy, a mathematical model based on the convection–diffusion equation was developed to simulate passive drug permeation across skin layers. Analytical modeling, solved using a closed-form solution, captured diffusion kinetics and flow patterns, while numerical modeling validated the results through finite element analysis. The model exhibited strong agreement with experimental data (relative error: ±12%) for both drugs, at an initial concentration of 1 mg mL⁻¹. Our microfluidic SoC device, functionally verified using experimental and in silico-assisted approaches, offers a reliable pre-clinical tool for testing chemicals, cosmetics, pharmaceuticals, and allergens. The investigations support a step forward in the use of new approach methodologies (NAMs) for improving predictive accuracy and standardizing drug permeability assays during the drug development process.

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Lipid nanoparticles (LNPs) have emerged as a promising drug delivery system due to their biocompatibility, biodegradability, and ability to deliver a wide range of therapeutic agents. While conventional bulk synthesis of LNPs results in batch-to-batch variability in particle physiochemical properties, microfluidic-based synthesis enables highly controllable outcomes. In recent years, acoustics have emerged as a powerful tool for LNP synthesis due to its flexibility and contactless operation. However, implementing acoustic-based methods in microfluidic devices usually requires precise microstructure fabrication within the channels, limiting scalability for large-scale synthesis. To overcome these challenges, we present a 3D-printed microfluidic device equipped with an acoustically driven, vibrating sharp-tip glass capillary, engineered to accommodate a wide range of flow rates and enable the scalable production of phosphatidylcholine (POPC) liposomes. Additionally, the impact of crucial parameters including total flow rates and flow rate ratios on the final product was assessed. To validate the results obtained from the sharp-tip mixing method, we compared the device with two widely used microfluidic devices for synthesizing liposomes: the NanoAssembler™ Ignite™ NxGen mixing device and the commercial herringbone mixing device. The mixing characterization results demonstrated that the sharp-tip mixer microfluidic device achieved optimal mixing across a broad range of total flow rates, from 30 µL/min to 3500 µL/min. Size distribution characterization of the final products showed that the sharp-tip mixer device produces homogeneous POPC liposomes with tunable sizes ranging from 60 to 150 nm.

High-purity fractionation of microparticles of different particle features is of great importance, especially in clinical diagnosis, recycling applications, and the food industry. We show that high-purity particle separation driven purely by hydrodynamic effects in a microchannel can be realized, achieving not only size, but also density and shape fractionation. For this, a microchannel with periodic contraction-expansion sections is used. A key feature of the method is that the Reynolds number at which a transition between particle equilibrium focusing regimes occurs decreases with increasing particle size, density, or aspect ratio. The evolution of inertial lift forces and centrifugal forces acting on individual particles is studied based on experimentally-determined, local features of the flow field, to gain a deeper insight into the particle migration dynamics. For this purpose, the General Defocusing Particle Tracking method is employed to reconstruct the three-dimensional positions of ellipsoidal and spherical particles. By enabling efficient, purely hydrodynamic separation of microparticles based on size, density, and shape, this approach opens new possibilities for passive separation in microfluidic applications.

In alignment with the UN Sustainable Development Goals (SDGs), performing research in the most feasible, reproducible, economical, and environmentally friendly way is important. Microfluidic systems are platforms where fluids are controlled on a micro-scale. They use small channels in the range of micrometers to rapidly process the fluids used in the study. This can further mimic many biological systems for studies. With the recent advances in the field of microfluidics, it has been used in the field of biomedical engineering. This review starts with the principle behind microfluidics, which has two parts. The first part of the review widely explains its applications in various biomedical research, including diagnostics, analytical, and therapeutic evaluation techniques. The second part of the review highlights the importance of microfluidics in orthopedic research concerning implant evaluation, drug development, printing scaffolds, and biomechanics aspects. Further, it highlights the applications of microfluidic systems, discusses their futuristic potential, and underscores the advancement of microfluidics in clinical diagnostics and biomedical research.