Search

The versatility, rapid development, and ease of production scalability of mRNA therapeutics have placed them at the forefront of biopharmaceutical research. However, despite their vast potential to treat diseases, their novelty comes with unsolved analytical challenges. A key challenge in ensuring sample purity has been monitoring residual, immunostimulatory dsRNA impurities generated during the in vitro transcription of mRNA. Here, we present a method that combines an enzyme, S1 nuclease, to identify and isolate dsRNA from an mRNA sample with a microfluidic electrophoresis analytical platform to characterize the impurity. After the method was developed and optimized, it was tested with clinically relevant, pseudouridine-modified 700 and 1800 bp dsRNA and 818–4451 nt mRNA samples. While the treatment impacted the magnitude of the fluorescent signal used to analyze the samples due to the interference of the buffer with the labeling of the sample, this signal loss was mitigated by 8.8× via treatment optimization. In addition, despite the mRNA concentration being up to 400× greater than that of the dsRNA, under every condition, there was a complete disappearance of the main mRNA peak. While the mRNA peak was digested, the dsRNA fragments remained physically unaffected by the treatment, with no change to their migration time. Using these samples, we detected 0.25% dsRNA impurities in mRNA samples using 15 μL with an analytical runtime of 1 min per sample after digestion and were able to predict their size within 8% of the expected length. The short runtime, sample consumption, and high throughput compatibility make it suitable to support the purity assessment of mRNA during purification and downstream. [ABSTRACT FROM AUTHOR]

Cell-cell interactions in the central nervous system play important roles in neurologic diseases. However, little is known about the specific molecular pathways involved, and methods for their systematic identification are limited. Here, we developed a forward genetic screening platform that combines CRISPR-Cas9 perturbations, cell coculture in picoliter droplets, and microfluidic-based fluorescence-activated droplet sorting to identify mechanisms of cell-cell communication. We used SPEAC-seq (systematic perturbation of encapsulated associated cells followed by sequencing), in combination with in vivo genetic perturbations, to identify microglia-produced amphiregulin as a suppressor of disease-promoting astrocyte responses in multiple sclerosis preclinical models and clinical samples. Thus, SPEAC-seq enables the high-throughput systematic identification of cell-cell communication mechanisms.

Recent years have seen continued expansion of the functionality of lab on a chip (LOC) devices. Indeed LOCs now provide scientists and developers with useful and versatile platforms across a myriad of chemical and biological applications. The field still fails, however, to integrate an often important element of bench-top analytics: real-time molecular measurements that can be used to guide a chemical response. Here we describe the analytical techniques that could provide LOCs with such real-time molecular monitoring capabilities. It appears to us that, among the approaches that are general (i.e., that are independent of the reactive or optical properties of their targets), sensing strategies relying on binding-induced conformational change of bioreceptors are most likely to succeed in such applications.

Numerous immunoassays have been successfully integrated on disc-based centrifugal platforms (CDs) over the last 20 years. These CD devices can be used as portable point-of-care (POC) platforms with sample-to-answer capabilities where bodily fluids such as whole blood can be used as samples directly without pre-processing. In order to use whole blood as a sample on CDs, centrifugation is used to separate red blood cells from plasma on CDs. There are several techniques for using specific fluidic patterns in the centrifugal fluidic network, such as reciprocation, that enhances the sensitivity of the immunoassays, including those using microarray antigen membranes. Present work demonstrates, for the first time, simultaneous integration of blood plasma separation (BPS) and reciprocation on the CD platform. The integrated design allows plasma that is separated from the red blood cells in a sedimentation chamber to flow into the reciprocation chamber via a narrow connecting channel of 0.5 mm × 0.5 mm cross-section. Due to the small cross-section of the connecting channel, there is no inflow of the red blood cell into the reciprocation chamber during subsequent fluidic operations of the CD. While no inflow of the red blood cells into the reciprocation chamber was observed, the conditions of 20 g jerk acceleration were also simulated in ANSYS finite element analysis software, and it was found that the CD design that was used is capable of retaining red blood cells in the sedimentation chamber. Experimentally, the isolation of red blood cells in the sedimentation chamber was confirmed using the ImageJ image processor to detect the visible color-based separation of the plasma from the blood. A fluorescent analyte testing on the bio-sensing array of the presented novel integrated design and on the standard reciprocation design CD was conducted for 7 min of reciprocation in each case. The test analyte was Europium Streptavidin Polystyrene analyte (10-3 mg/mL) and the microarray consisted of Biotin bovine serum albumin (BSA) dots. The fluorescent signals for the standard and integrated designs were nearly identical (within the margin of error) for the first several minutes of reciprocation, but the fluorescent signal for the integrated design was significantly higher when the reciprocation time was increased to 7 min.

The utilizations of microfluidic chips for single RBC (red blood cell) studies have attracted great interests in recent years to filter, trap, analyze, and release single erythrocytes for various applications. Researchers in this field have highlighted the vast potential in developing micro devices for industrial and academia usages, including lab-on-a-chip and organ-on-a-chip systems. This article critically reviews the current state-of-the-art and recent advances of microfluidics for single RBC analyses, including integrated sensors and microfluidic platforms for microscopic/tomographic/spectroscopic single RBC analyses, trapping arrays (including bifurcating channels), dielectrophoretic and agglutination/aggregation studies, as well as clinical implications covering cancer, sepsis, prenatal, and Sickle Cell diseases. Microfluidics based RBC microarrays, sorting/counting and trapping techniques (including acoustic, dielectrophoretic, hydrodynamic, magnetic, and optical techniques) are also reviewed. Lastly, organs on chips, multi-organ chips, and drug discovery involving single RBC are described. The limitations and drawbacks of each technology are addressed and future prospects are discussed.

The manipulation of magnetic microparticles has always been pivotal in the development of microfluidic devices, as it encompasses a broad range of applications, such as drug delivery, bioanalysis, on-chip diagnostics, and more recently organ-on-chip development. However, predicting the behavior and trajectory of these particles remains a recurring and partly unresolved question. Magnetic particle-laden flows can display intricate collective behaviors, such as packed plugs, column-shaped aggregates, or fluidization, which are difficult to predict. In this study, we introduce a finite-element model to simulate highly dense flows of magnetic microparticles. Our method relies on an interpenetrating continuum approach, where both the liquid and particle phases are described by the Navier–Stokes equations, in which the magnetic force, interphase friction, and interparticle forces were included. We demonstrate its applicability across the entire range of particle packing densities and compare the results with experimental data from real microfluidic application cases. The model successfully replicates complex behaviors, such as particle aggregation, plug formation and fluidization. This approach has potential to accelerate microfluidic device development by reducing the need for costly and time-consuming experimental optimization. [ABSTRACT FROM AUTHOR]

The riparian zone, found alongside rivers and streams, is a unique habitat characterized by its vulnerability to sudden floods following intense rainfall. To cope with these challenging conditions, a specific group of plants with linear and lanceolate lamina have adapted to thrive in these environments. Despite their unique ability to withstand the forceful water flow, the specific adaptive characteristics of the petioles, which support the lamina remain unknown. Our morphological, anatomical, and mechanical analyses on the petioles of Osmunda lancea (Osmundaceae) along the river and an inland sister species of O. japonica revealed that the petioles of O. lancea had a larger cell volume in subepidermal cortex and were more flexible than those of O. japonica. [ABSTRACT FROM AUTHOR]

From their initial application to the fields of chemistry and biology, microfluidic chips used as micro total analysis systems have developed into new technologies to satisfy the requirements of various societal industries. Microchannels are essential components of microfluidic chips; they play a vital role in connecting the inlet and outlet as well as determining the flow distribution and reagent mixing. Microfluidic research has always been devoted to minimizing energy dissipation, fluid resistance, and pressure drop to realize energy-efficient microfluidic chips. This study proposes a new theory for manipulating the flow in microchannels based on hydrodynamic metamaterials according to the spatial transformation theory. In particular, hydrodynamic metamaterials are specifically designed to construct flow shifters, flow splitters, and flow combiners, and theoretical and numerical simulations are performed to assess their hydrodynamic performance. The systematic design of hydrodynamic metamaterial devices proposed in this work establishes a theoretical framework to achieve a steady flow state without inducing unstable flow disturbances in complex-shape microchannels. [ABSTRACT FROM AUTHOR]

Background: The functional heterogeneity of culture-expanded mesenchymal stem cells (MSCs) has hindered the clinical application of MSCs. Previous studies have shown that MSC subpopulations with superior chondrogenic capacity can be isolated using a spiral microfluidic device based on the principle of inertial cell focusing. Hypothesis: The delivery of microfluidic-enriched chondrogenic MSCs that are consistent in size and function will overcome the challenge of the functional heterogeneity of expanded MSCs and will significantly improve MSC-based cartilage repair. Study Design: Controlled laboratory study. Methods: A next-generation, fully automated multidimensional double spiral microfluidic device was designed to provide more refined and efficient isolation of MSC subpopulations based on size. Analysis of in vitro chondrogenic potential and RNA sequencing was performed on size-sorted MSC subpopulations. In vivo cartilage repair efficacy was demonstrated in an osteochondral injury model in 12-week-old rats. Defects were implanted with MSC subpopulations (n = 6 per group) and compared with those implanted with unsegregated MSCs (n = 6). Osteochondral repair was assessed at 6 and 12 weeks after surgery by histological, micro–computed tomography, and mechanical analysis. Results: A chondrogenic MSC subpopulation was efficiently isolated using the multidimensional double spiral device. RNA sequencing revealed distinct transcriptomic profiles and identified differential gene expression between subpopulations. The delivery of a chondrogenic MSC subpopulation resulted in improved cartilage repair, as indicated by histological scoring, the compression modulus, and micro–computed tomography of the subchondral bone. Conclusion: We have established a rapid, label-free, and reliable microfluidic protocol for more efficient size-based enrichment of a chondrogenic MSC subpopulation. Our proof-of-concept in vivo study demonstrates the enhanced cartilage repair efficacy of these enriched chondrogenic MSCs. Clinical Relevance: The delivery of microfluidic-enriched chondrogenic MSCs that are consistent in size and function can overcome the challenge of the functional heterogeneity of expanded MSCs, resulting in significant improvement in MSC-based cartilage repair. The availability of such rapid, label-free enriched chondrogenic MSCs can enable better cell therapy products for cartilage repair with improved treatment outcomes. [ABSTRACT FROM AUTHOR]

• Linear cooling of continuous microfluidic was achieved based on a single TEC. • Multi-structure TEC was proposed to generate a linear temperature gradient. • Numerical model was established and verified by experiment. • Linearity, cooling rate and temperature of linear cooling were analyzed. • Cooling rate can be controlled by changing the current and microfluidic velocity. Linear cooling of continuous microfluidic is crucial to the microfluidic analysis of cell cryopreservation and homogenous ice nucleation. This study presents a method to establish a linear temperature gradient for linear cooling of continuous microfluidic based on a single thermoelectric cooler. A novel multi-structure thermoelectric cooler was proposed to generate a stable linear temperature gradient. Furthermore, a numerical model was established to explore the performance of linear cooling of continuous microfluidic. Meanwhile, experiments were carried out to validate the model. Based on the proposed multi-structure thermoelectric cooler, linear cooling of continuous microfluidic can be successfully achieved, even if the current of the thermoelectric cooler or microfluidic velocity changes. For the case of current equal to 3 A and microfluidic velocity equal to 50 mm/s, microfluidic can be linearly cooled from 297 K to 251 K with a cooling rate of 64.5 K/s and linearity of 0.9912. It was also found that the temperature gradient decreases slightly with increasing microfluidic velocity while the cooling rate increases and is approximately proportional to the microfluidic velocity. With the increase of microfluidic velocity , the linearity increases at first and then decreases. Maximum goodness of fit equal to 0.9942 appears at the microfluidic velocity of 20 mm/s. [ABSTRACT FROM AUTHOR]

Mixing of the algal culture medium in a photobioreactor (PBR) is a crucial factor to enhance microalgae cultivation and production, since it ensures microalgae cells can homogeneously access nutrients and light radiation. Hydrodynamic conditions in an industrially applicable PBR cannot be tested in laboratory cultivation systems since the scale-up methodology is not specified; hence requiring complex tests at a demonstrative scale or the application of mathematical models. In this study, a three-dimensional numerical model of the hydrodynamic conditions in a hybrid horizontal tubular PBR was developed to investigate the mixing of the culture medium under various operating conditions, in order to optimize biomass production in this type of system. The PBR consists of two open tanks connected through sixteen polyethylene transparent tubes, at a demonstrative scale (total volume 11.7 m3). Microalgae cells movement inside the tubes was simulated. Cell trajectory prediction allows to simulate the intensity of mixing of the culture medium. Subsequent coupling with the biokinetic BIO_ALGAE model allows to monitor the influence of hydrodynamic conditions on the distribution of light in the culture medium and the yield of microalgae. The simulations were experimentally validated. The more intense mixing of the culture medium caused by increasing flow rate (Re = 23,700–46,200) allows more frequent exposure of the microalgae cells to the light source, which according to the results obtained can increase the microalgal yield by 14% in the summer cultivation period and by 151% in the winter period. [Display omitted] [ABSTRACT FROM AUTHOR]

The utilization of microfluidic analysis technology has resulted in the advancement of fast pathogenic bacteria detection, which can accurately provide information on biochemical reactions in a single cell and enhance detection efficiency. Nevertheless, the achievement of rapid and effective in situ detection of single-bacteria arrays remains a challenge due to the complexity of bacterial populations and low Reynolds coefficient fluid, resulting in insufficient diffusion. We develop microwell droplet array chips from the lateral hydrodynamic wetting approach to address this issue. The sidewall of the microwell gradually opens which aids in advancing the liquid–air interface and facilitates the impregnation of the solid microwells, preserving the Wenzel state and assisting in resisting the liquid force to separation from the drop. The feasibility of preparing cell arrays and identifying them inside the microwells was demonstrated through the simulated streamlined distribution of gradual and traditional microwells with different sizes. The water-based ink diffusion experiment examined the relationship between diffusion efficiency and flow velocity, as well as the position of the microwell relative to the channel. It showed that the smaller gradual microwell still has a good diffusion efficiency rate at a flow velocity of 2.1 μL min−1 and that the infiltration state is easier to adjust. With this platform, we successfully isolated a mixed population containing E. coli and S. aureus, obtained single-bacteria arrays, and performed Gram assays after in situ propagation. After 20 hours of culture, single bacteria reproduced demonstrating the capability of this platform to isolate, cultivate, and detect pathogenic bacteria. [ABSTRACT FROM AUTHOR]

Simple Summary: Cancer is the main cause of human death. Nanomedicine provides a new strategy for the treatment of diverse cancers. Among them, superparamagnetic artificial cell PLGA-Fe3O4 micro/nanocapsules demand great attention due to their excellent properties, such as targeted delivery, magnetic response, and biocompatibility. The aim of this review is to summarize the application of superparamagnetic artificial cells (PLGA-Fe3O4) micro/nanocapsules in cancer drug targeted delivery and their preparation methods, providing insights into the future development of superparamagnetic artificial cells (PLGA nano/microcapsules) for magnetic targeting in cancer treatment. Artificial cells have been extensively used in many fields, such as nanomedicine, biotherapy, blood substitutes, drug delivery, enzyme/gene therapy, cancer therapy, and the COVID-19 vaccine. The unique properties of superparamagnetic Fe3O4 nanoparticles have contributed to increased interest in using superparamagnetic artificial cells (PLGA-Fe3O4 micro/nanocapsules) for targeted therapy. In this review, the preparation methods of Fe3O4 NPs and superparamagnetic artificial cell PLGA-drug-Fe3O4 micro/nanocapsules are discussed. This review also focuses on the recent progress of superparamagnetic PLGA-drug-Fe3O4 micro/nanocapsules as targeted therapeutics. We shall concentrate on the use of superparamagnetic artificial cells in the form of PLGA-drug-Fe3O4 nanocapsules for magnetic hyperthermia/photothermal therapy and cancer therapies, including lung breast cancer and glioblastoma. [ABSTRACT FROM AUTHOR]

Flow cytometry is an essential technique in single particle analysis and cell sorting for further downstream diagnosis, exhibiting high-throughput and multiplexing capabilities for many biological and biomedical applications. Although many hydrodynamic focusing-based microfluidic cytometers have been demonstrated with reduced size and cost to adapt to point-of-care settings, the operating conditions are not characterized systematically. This study presents the flow transition process in the hydrodynamic focusing mechanism when the flow rate or the Reynolds number increases. The characteristics of flow fields and mass transport were studied under various operating conditions, including flow rates and microchannel heights. A transition from the squeezed focusing state to the over-squeezed anti-focusing state in the hydrodynamic focusing regime was observed when the Reynolds number increased above 30. Parametric studies illustrated that the focusing width increased with the Reynolds number but decreased with the microchannel height in the over-squeezed state. The microfluidic cytometric analyses using microbeads and E. coli show that the recovery rate was maintained by limiting the Reynolds number to 30. The detailed analysis of the flow transition will provide new insight into microfluidic cytometric analyses with a broad range of applications in food safety, water monitoring and healthcare sectors. [ABSTRACT FROM AUTHOR]

The manipulation and control of particles in microfluidic devices through non-intrusive methods is pivotal in many application fields, e.g., cell focusing and sorting. Inertial microfluidics is rapidly gaining attention in the scientific community because of the considerable advantages in terms of throughput. In addition to inertia, other factors can trigger the cross-stream migration of particles in liquids undergoing pressure-driven channel flows, such as the deformability of the particles themselves and/or the viscoelasticity of the carrier fluid. For this reason, the dynamics of an initially spherical elastic particle suspended in a viscoelastic liquid subjected to pressure-driven flow in a cylindrical channel at non-negligible inertia is studied through three-dimensional arbitrary Lagrangian–Eulerian finite-element numerical simulations. The mechanical behavior of the particle is described through the neo-Hookean hyper-elastic constitutive equation, whereas the rheological behavior of the carrier liquid is described through the Giesekus model. The Reynolds number Re, measuring the relative importance of inertial and viscous forces in the tube, the elastic capillary number Ca e , measuring the relative importance of liquid viscous stress and solid elastic stress, and the Deborah number De, measuring the ratio of the liquid relaxation time and the flow characteristic time, are varied. The particle migrates transversally to the flow direction until reaching a radial equilibrium position depending on Re, Ca e , and De. Different dynamics are observed depending on the interplay among inertia and elasticity of both the liquid and the solid phase: one, two, or even three stable equilibrium positions can be found along the tube radius. [ABSTRACT FROM AUTHOR]

In the field of tissue engineering, local hypoxia in large-cell structures (larger than 1 mm3) poses a significant challenge. Oxygen-releasing biomaterials supply an innovative solution through oxygen ⁠ delivery in a sustained and controlled manner. Compared to traditional methods such as emulsion, sonication, and agitation, microfluidic technology offers distinct benefits for oxygen-releasing material production, including controllability, flexibility, and applicability. It holds enormous potential in the production of smart oxygen-releasing materials. This review comprehensively covers the fabrication and application of microfluidic-enabled oxygen-releasing biomaterials. To begin with, the physical mechanism of various microfluidic technologies and their differences in oxygen carrier preparation are explained. Then, the distinctions among diverse oxygen-releasing components in regards for oxygen-releasing mechanism, oxygen-carrying capacity, and duration of oxygen release are presented. Finally, the present obstacles and anticipated development trends are examined together with the application outcomes of oxygen-releasing biomaterials based on microfluidic technology in the biomedical area. Oxygen is essential for sustaining life, and hypoxia (a condition of low oxygen) is a significant challenge in various diseases. Microfluidic-based oxygen-releasing biomaterials offer precise control and outstanding performance, providing unique advantages over traditional approaches for tissue engineering. However, comprehensive reviews on this topic are currently lacking. In this review, we provide a comprehensive analysis of various microfluidic technologies and their applications for developing oxygen-releasing biomaterials. We compare the characteristics of organic and inorganic oxygen-releasing biomaterials and highlight the latest advancements in microfluidic-enabled oxygen-releasing biomaterials for tissue engineering, wound healing, and drug delivery. This review may hold the potential to make a significant contribution to the field, with a profound impact on the scientific community. [Display omitted] [ABSTRACT FROM AUTHOR]

The handling and analysis of gaseous tritium is of interest for hydrogen isotope separation experiments. In this work, we present an easy-to-handle setup for catalytic oxidation to HTO, recovering all of the initially dosed gaseous tritium as determined by LSC, using CuO as a catalyst at a reaction temperature of 900 °C. Aiming to reduce cocktail waste, the LSC determination was downscaled to a microfluidic setup. The performance was evaluated based on the counting efficiency, which was shown to decrease significantly, as the sample volume was reduced to µl amounts, while no changes were observed over a wide range of sample-to-cocktail ratios. [ABSTRACT FROM AUTHOR]

The GeneSoC® that launched recently enables the quantitative detection of target genes (in approximately 15 min) using microfluidic thermal cycling technology. Here, we compared the diagnostic performance of the "GeneSoC® SARS-CoV-2 N2 Detection Kit" (Kyorin assay) and conventional severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) detection assays to verify the clinical usefulness of the Kyorin assay. Two hundred samples (100 nasopharyngeal and 100 saliva specimens) were collected from patients with suspected SARS-CoV-2 infection between May 2020 and August 2021. Conventional SARS-CoV-2 detection assays were performed using the Japanese National Institute of Infectious Diseases (NIID) assay, Ampdirect™ 2019-nCoV Detection Kit (SHIMADZU assay), and Lumipulse Presto SARS-CoV-2 Ag (FUJIREBIO assay), according to each manufacturer's instructions. Using the NIID and SHIMADZU assays as references, the positive and negative concordance rates and the kappa coefficient in the Kyorin assay were 96.9–97.9 %, 99.0–100.0 %, and 0.96–0.98, respectively. The positivity rate of the FUJIREBIO assay was slightly lower than that of the reference assay (p<0.05). The Kyorin assay showed a favorable concordance rate with conventional SARS-CoV-2 detection assays, making it a useful, rapid, and high-performance assay for detecting SARS-CoV-2, which may lead to early diagnosis and appropriate treatment. [ABSTRACT FROM AUTHOR]

In drop-based microfluidics, an aqueous sample is partitioned into drops using individual pump sources that drive water and oil into a drop-making device. Parallelization of drop-making devices is necessary to achieve high-throughput screening of multiple experimental conditions, especially in time-sensitive studies. Here, we present the plate-interfacing parallel encapsulation (PIPE) chip, a microfluidic chip designed to generate 50 to 90 μm diameter drops of up to 96 different conditions in parallel by interfacing individual drop makers with a standard 384-well microtiter plate. The PIPE chip is used to generate two types of optically barcoded drop libraries consisting of two-color fluorescent particle combinations: a library of 24 microbead barcodes and a library of 192 quantum dot barcodes. Barcoded combinations in the drop libraries are rapidly measured within a microfluidic device using fluorescence detection and distinct barcoded populations in the fluorescence drop data are identified using DBSCAN data clustering. Signal analysis reveals that particle size defines the source of dominant noise present in the fluorescence intensity distributions of the barcoded drop populations, arising from Poisson loading for microbeads and shot noise for quantum dots. A barcoded population from a drop library is isolated using fluorescence-activated drop sorting, enabling downstream analysis of drop contents. The PIPE chip can improve multiplexed high-throughput assays by enabling simultaneous encapsulation of barcoded samples stored in a microtiter plate and reducing sample preparation time.

Superhydrophobic surface-based optofluidics have been introduced to biosensors and unconventional optics with unique advantages, such as low light loss and power consumption. However, most of these platforms were made with planar-like microstructures and nanostructures, which may cause bonding issues and result in significant waveguide loss. Here, we introduce a fully enclosed superhydrophobic-based optofluidics system, enabled by a one-step microstereolithography procedure. Various microstructured cladding designs with a feature size down to 100 μm were studied and a T-type overhang design exhibits the lowest optical loss, regardless of the excitation wavelength. Surprisingly, the optical loss of superhydrophobic-based optofluidics is not solely decided by the solid area fraction at the solid/water/air interface, but also the cross-section shape and the effective cladding layer composition. We show that this fully enclosed optofluidic system can be used for CRISPR-labeled quantum dot quantification, intended for in vitro and in vivo CRISPR therapeutics.

Protein networks can be assembled in vitro for basic biochemistry research, drug screening, and the creation of artificial cells. Two standard methodologies are used: manual pipetting and pipetting robots. Manual pipetting has limited throughput in the number of input reagents and the combination of reagents in a single sample. While pipetting robots are evident in improving pipetting efficiency and saving hands-on time, their liquid handling volume usually ranges from a few to hundreds of microliters. Microfluidic methods have been developed to minimize the reagent consumption and speed up screening but are challenging in multifactorial protein studies due to their reliance on complex structures and labeling dyes. Here, we engineered a new impact-printing-based methodology to generate printed microdroplet arrays containing water-in-oil droplets. The printed droplet volume was linearly proportional (R2 = 0.9999) to the single droplet number, and each single droplet volume was around 59.2 nL (coefficient of variation = 93.8%). Our new methodology enables the study of protein networks in both membrane-unbound and -bound states, without and with anchor lipids DGS-NTA(Ni), respectively. The methodology is demonstrated using a subnetwork of mitogen-activated protein kinase (MAPK). It takes less than 10 min to prepare 100 different droplet-based reactions, using

Current methods for fabricating microparticles offer limited control over size and shape. Here, we demonstrate a droplet microfluidic method to form polyhedral microparticles with controlled concavity. By manipulating Laplace pressure, buoyancy, and particle rheology, we generate microparticles with diverse shapes and curvatures. Additionally, we demonstrate the particles provide increased capture efficiency when used for particle-templated emulsification. Our approach enables microparticles with enhanced chemical and biological functionality.

Droplet-based microfluidic systems have been employed to manipulate discrete fluid volumes with immiscible phases. Creating the fluid droplets at microscale has led to a paradigm shift in mixing, sorting, encapsulation, sensing, and designing high throughput devices for biomedical applications. Droplet microfluidics has opened many opportunities in microparticle synthesis, molecular detection, diagnostics, drug delivery, and cell biology. In the present review, we first introduce standard methods for droplet generation (i.e. passive and active methods) and discuss the latest examples of emulsification and particle synthesis approaches enabled by microfluidic platforms. Then, the applications of droplet-based microfluidics in different biomedical applications are detailed. Finally, a general overview of the latest trends along with the perspectives and future potentials in the field are provided.

Waterborne diseases cause millions of deaths worldwide, especially in developing communities. The monitoring and rapid detection of microbial pathogens in water is critical for public health protection. This study reports the development of a proof-of-concept portable pathogen analysis system (PPAS) that can detect bacteria in water with the potential application in a point-of-sample collection setting. A centrifugal microfluidic platform is adopted to integrate bacterial cell lysis in water samples, nucleic acid extraction, and reagent mixing with a droplet digital loop mediated isothermal amplification assay for bacteria quantification onto a single centrifugal disc (CD). Coupled with a portable "CD Driver" capable of automating the assay steps, the CD functions as a single step bacterial detection "lab" without the need to transfer samples from vial-to-vial as in a traditional laboratory. The prototype system can detect Enterococcus faecalis, a common fecal indicator bacterium, in water samples with a single touch of a start button within 1 h and having total hands-on-time being less than 5 min. An add-on bacterial concentration cup prefilled with absorbent polymer beads was designed to integrate with the pathogen CD to improve the downstream quantification sensitivity. All reagents and amplified products are contained within the single-use disc, reducing the opportunity of cross contamination of other samples by the amplification products. This proof-of-concept PPAS lays the foundation for field testing devices in areas needing more accessible water quality monitoring tools and are at higher risk for being exposed to contaminated waters.

Shan Chen,1 Houming Liu,1 Tianpin Li,1 Wenjie Lai,1 Lei Liu,1 Youchun Xu,2 Jiuxin Qu1 1Department of Clinical Laboratory, Shenzhen Third People’s Hospital, National Clinical Research Center for Infectious Diseases, The Second Affiliated Hospital of Southern University of Science and Technology, Shenzhen, Guangdong Province, 518112, People’s Republic of China; 2Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing, 100084, People’s Republic of ChinaCorrespondence: Jiuxin Qu, Department of Clinical Laboratory, Shenzhen Third People’s Hospital, National Clinical Research Center for Infectious Diseases, The Second Affiliated Hospital of Southern University of Science and Technology, Shenzhen, People’s Republic of China, Email Qujiuxin@163.com Youchun Xu, Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing, People’s Republic of China, Email CYX040198@163.comBackground: The currently used conventional susceptibility testing for drug-resistant Mycobacterium tuberculosis (M.TB) is limited due to being time-consuming and having low efficiency. Herein, we propose the use of a microfluidic-based method to rapidly detect drug-resistant gene mutations using Kompetitive Allele-Specific PCR (KASP).Methods: A total of 300 clinical samples were collected, and DNA extraction was performed using the “isoChip®” Mycobacterium detection kit. Phenotypic susceptibility testing and Sanger sequencing were performed to sequence the PCR products. Allele-specific primers targeting 37 gene mutation sites were designed, and a microfluidic chip (KASP) was constructed using 112 reaction chambers to simultaneously detect multiple mutations. Chip validation was performed using clinical samples.Results: Phenotypic susceptibility of clinical isolates revealed 38 rifampicin (RIF)-resistant, 64 isoniazid (INH)-resistant, 48 streptomycin (SM)-resistant and 23 ethambutol (EMB)-resistant strains, as well as 33 multi-drug-resistant TB (MDR-TB) strains and 20 strains fully resistant to all four drugs. Optimization of the chip-based detection system for drug resistance detection showed satisfactory specificity and maximum fluorescence at a DNA concentration of 1× 101 copies/μL. Further analysis revealed that 76.32% of the RIF-resistant strains harbored rpoB gene mutations (sensitivity, 76.32%; specificity 100%), 60.93% of the INH-resistant strains had katG gene mutations (sensitivity, 60.93%; specificity, 100%), 66.66% of the SM-resistant strains carried drug resistance gene mutations (sensitivity, 66.66%; specificity, 99.2%), and 69.56% of the EMB-resistant strains had embB gene mutations (sensitivity, 69.56%; specificity, 100%). Further, the overall agreement between the microfluidic chip and Sanger sequencing was satisfactory, with a turnaround time of the microfluidic chip was approximately 2 hours, much shorter than the conventional DST method.Conclusion: The proposed microfluidic-based KASP assay provides a cost-effective and convenient method for detecting mutations associated with drug resistance in M. tuberculosis. It represents a promising alternative to the traditional DST method, with satisfactory sensitivity and specificity and a much shorter turnaround time.Graphical Abstract: Keywords: Mycobacterium tuberculosis, multidrug-resistance, drug resistance, resistance-conferring gene mutations, polymerase chain reaction, microfluidic analytical techniques, Sanger sequencing

Fluid–rock interaction within the altered oceanic crust and across the slab–mantle boundary during subduction facilitates element transfer, but the dynamics of fluid transport and fluid–rock exchange during upward fluid migration are still unclear. A study of metamorphic fluid–rock interaction within a section of subducted oceanic crust was carried out on eclogites and metasediments of the ultra-high-pressure Lago di Cignana Unit (NW Italian Alps). The P–T modeling of a quartzschist shows that garnet grew during the prograde and sporadically during the retrograde path and that phengite mainly records the peak to retrograde conditions. Microscale geochemical analysis of garnets has revealed a systematic evolution of oxygen isotopic composition with garnet major element zonation, with extreme within-sample core–rim variations in δ18O between 18 and 4‰ providing evidence for external fluid influx. Garnet in eclogites and calcschists, as well as garnet cores in quartz-rich lithologies, shows normal compositional zoning, as expected for prograde garnet growth, and a relatively constant oxygen isotopic composition. The outer garnet growth zones within a few metasediments show reverse or discontinuous zoning and progressively lower δ18O. Despite major element zoning, the isotopic composition of mica is homogeneous across chemical zoning in one eclogite and one quartzschist, but shows 6‰ variability in another quartzschist. In the underlying Zermatt–Saas serpentinites, antigorite from nine serpentinite samples shows some variation in δ18O, with average δ18O values for individual samples ranging from 1 to 6‰. These results provide evidence for two main stages of external fluid infiltration: (i) fluids from the dehydration of mafic lithologies entered the sequence at peak conditions around 3 GPa, as indicated by the oxygen composition of intermediate zones of mica and garnet, and (ii) low δ18O fluids from serpentinites infiltrated parts of the sedimentary package during exhumation prior to 1.5 GPa, as recorded by the 4‰ garnet outer rims. Samples recording external fluid infiltration are concentrated in the lower part of the sequence, indicating channelized fluid flow, suggesting focused fluid infiltration due to permeability contrasts between metasedimentary and eclogitic lithologies. Channelized fluid flow in the ultra-high-pressure metasediments of Lago di Cignana has not resulted in systematic decarbonation of the metasediments. [ABSTRACT FROM AUTHOR]

The emergence of exceptional points in a non‐Hermitian system has provided intriguing possibilities to enhance the sensitivity of a sensor, while it is yet a considerable challenge to implement subwavelength non‐Hermitian systems. One possible solution to tackle this challenge is to take advantage of localized surface plasmon resonances, which enable large electromagnetic enhancement at the subwavelength scale. In this work, a novel sensing scheme based on the exceptional points in a spoof plasmonic structure working at microwave frequencies is proposed. It is shown that near‐field plasmonic vortices can be efficiently generated at the exceptional points, resulting in the enhanced sensitivity when detecting a single particle or fluid analytes. Single particle detection with the particle size as small as 1/100 of the operating wavelength is reported. For liquid analysis in the microfluidic system, the sample consumption is down to 0.72 μL. This work demonstrates the ultrahigh sensitivity of exceptional‐point‐based plasmonic sensing and opens up new possibilities for subwavelength and compact sensors operating in the microwave, terahertz, and even far‐infrared regions. [ABSTRACT FROM AUTHOR]

Wireless, skin‐interfaced electronic and microfluidic devices have the potential to replace wired, bulky, and cumbersome technologies for personal and clinical health monitoring, allowing care to extend from hospital settings to the home. For use on skin, these devices commonly employ silicone‐based thermoset elastomers (TSEs) as layers that encapsulate the electronics or serve as molded microchannels for biofluid (e.g., sweat) capture, storage, and analysis. Barriers to commercial adoption of such devices include difficulties in use of these elastomers in conventional practices for mass manufacturing. Their relatively high cost and inability to allow for recycling represent additional disadvantages. By contrast, thermoplastic elastomers (TPEs) are fully compatible with industrial‐scale manufacturing processes, low in cost, and recyclable. Like TSEs, TPEs are soft, stretchable, flexible, and optically transparent, while possessing other properties well‐suited for applications in wireless, skin‐interfaced devices. Herein, the characteristics, processing, and application techniques for three commercially available TPEs, including two thermoplastic polyurethanes as encapsulation layers for a wireless skin hydration sensor and one thermoplastic styrenic block copolymer for a microfluidic sweat analysis platform, are reported. The results demonstrate that TPEs can be effectively integrated into these classes of devices, as a compelling alternative to TSEs, as a mass‐manufacturable, sustainable materials option. [ABSTRACT FROM AUTHOR]

Contemporary personalized cancer diagnostic approaches encounter multiple challenges. The presence of cellular and molecular heterogeneity in patient samples introduces complexities to analysis protocols. Conventional analyses are manual, reliant on expert personnel, time-intensive, and financially burdensome. The copious data amassed for subsequent analysis strains the system, obstructing real-time diagnostics at the "point of care" and impeding prompt intervention. This study introduces PTOLEMI: Python-based Tensor Oncological Locator Examining Microfluidic Instruments. PTOLEMI stands out as a specialized system designed for high-throughput image analysis, particularly in the realm of microfluidic assays. Utilizing a blend of machine learning algorithms, PTOLEMI can process large datasets rapidly and with high accuracy, making it feasible for point-of-care diagnostics. Furthermore, its advanced analytics capabilities facilitate a more granular understanding of cellular dynamics, thereby allowing for more targeted and effective treatment options. Leveraging cutting-edge AI algorithms, PTOLEMI rapidly and accurately discriminates between cell viability and distinct cell types within biopsy samples. The diagnostic process becomes automated, swift, precise, and resource-efficient, rendering it well-suited for point-of-care requisites. By employing PTOLEMI alongside a microfluidic cell culture chip, physicians can attain personalized diagnostic and therapeutic insights. This paper elucidates the evolution of PTOLEMI and showcases its prowess in analyzing cancer patient samples within a microfluidic apparatus. While the integration of machine learning tools into biomedical domains is undoubtedly in progress, this study's innovation lies in the fusion of PTOLEMI with a microfluidic platform—an integrated, rapid, and independent framework for personalized drug screening-based clinical decision-making. [ABSTRACT FROM AUTHOR]

Over the past few decades, there has been a significant increase in the use of paper-based microfluidic devices in various fields, including environmental monitoring, food safety analysis, and medical diagnostics. As a result, flow through paper-based substrates has gained much attention in the research community. Liquid flows through a paper substrate due to the inherent capillary suction pressure. In order to predict the flow through a paper substrate, we used macro- and microscopic methodologies to construct an analytical and numerical model. We have considered the effect of different factors, e.g., roughness, swelling, dynamic contact angle, and evaporation simultaneously to predict liquid wicking. A modified capillary radius technique is used to incorporate the effects of roughness and swelling into the numerical model, while a sink factor in Darcy's equation is used to model the evaporation. Experiments are performed to validate the developed models, and it is found that both models are in good agreement with the experiments, with a maximum error of 5%. The proposed analytical and numerical models can be used to forecast the capillary rise in a paper-based substrate, which has implications for paper-based microfluidic devices. [ABSTRACT FROM AUTHOR]

Simple Summary: Macrophages, specifically tumor-associated macrophages (TAMs), play a vital role in inflammatory breast cancer (IBC) progression, including cell growth, angiogenesis, and resistance to treatment. Current in vitro models for studying IBC have limitations and do not fully capture the dynamic nature of interactions between macrophages, the tumor, and the microenvironment in IBC. Therefore, we have developed a 3D in vitro model of IBC that incorporates a collagen matrix, functional blood vessels, and THP1 M0, M1, or M2 macrophages, allowing for the study of macrophage-tumor interactions and angiogenesis. Using this platform, it was found that Incorporating TAMs increases the number of new vessel sprouts, permeability of the vessel, matrix porosity, and intravasation of MDA-IBC3 cells. Additionally, IL8 and MMP-9, which are known to promote angiogenesis and tumor invasion, were found to be preferentially secreted in M0 and M2 co-culture platforms. Inflammatory breast cancer (IBC) is an aggressive disease with a poor prognosis and a lack of effective treatments. It is widely established that understanding the interactions between tumor-associated macrophages (TAMs) and the tumor microenvironment is essential for identifying distinct targeting markers that help with prognosis and subsequent development of effective treatments. In this study, we present a 3D in vitro microfluidic IBC platform consisting of THP1 M0, M1, or M2 macrophages, IBC cells, and endothelial cells. The platform comprises a collagen matrix that includes an endothelialized vessel, creating a physiologically relevant environment for cellular interactions. Through the utilization of this platform, it was discovered that the inclusion of tumor-associated macrophages (TAMs) led to an increase in the formation of new blood vessel sprouts and enhanced permeability of the endothelium, regardless of the macrophage phenotype. Interestingly, the platforms containing THP-1 M1 or M2 macrophages exhibited significantly greater porosity in the collagen extracellular matrix (ECM) compared to the platforms containing THP-1 M0 and the MDA-IBC3 cells alone. Cytokine analysis revealed that IL-8 and MMP9 showed selective increases when macrophages were cultured in the platforms. Notably, intravasation of tumor cells into the vessels was observed exclusively in the platform containing MDA-IBC3 and M0 macrophages. [ABSTRACT FROM AUTHOR]

Detection and imaging of viruses in a complex solution is particularly significant for virology and requires a comprehensive understanding of biosensors. While lab-on-a-chip systems are used in virus detection as biosensors, analysis and optimization of these systems are especially challenging due to the size of the system to be used in the certain application. The system of interest for virus detection is required to be cost efficient and is also needed to be able to easily operable with a simple setup. Moreover, the detailed analysis of these microfluidic systems should be made with precision in order to predict the capabilities and the efficiency of the system accurately. This paper reports on the use of a common commercial computational fluid dynamics (cfd) software for the analysis of a microfluidic lab-on-a-chip virus detection cartridge. This study evaluates the problems commonly encountered during microfluidic applications of cfd softwares particularly in the area of reaction modeling of the antigen-antibody interaction. cfd analysis is later validated and combined with experiments to optimize the amount of dilute solution used in the tests. Thereafter, the geometry of the microchannel is also optimized and optimal test conditions are set for a cost efficient and effective virus detection kit using light microscopy. [ABSTRACT FROM AUTHOR]

The widespread consumption of plant-based drinks, driven by health and dietary reasons (including cow's milk allergy, lactose intolerance, milk protein intolerance, following a vegetarian or vegan diet) necessitates automated and accurate test methods. Our study demonstrates the simultaneous determination of protein components and total protein concentrations in plant-based milk alternatives using a rapid and reproducible microchip gel electrophoretic method. As expected, the electrophoretic profiles of each plant-based drink differed. Based on our analyses and statistical evaluation, it can be determined that the protein profiles of different plant-based beverages do not differ significantly between different manufacturers or different expiry dates. The measured total protein content was compared with the nominal values, i.e., the values stated on the beverage labels. As the number of consumers of functional and specialized plant-based milk alternatives continues to rise, it is important to prioritize methods that provide qualitative and quantitative information on protein composition and other nutrients. [ABSTRACT FROM AUTHOR]

As core parts of microfluidic chip analysis systems, micromixers show robust applications in wide fields. However, restricted by the fabrication technology, it remains challenging to achieve high-quality micromixers with both delicately designed structure and efficient mixing. In this study, based on the theory of chaotic mixing, sinusoidal structures with variable phases were designed and then fabricated through scanning probe lithography (SPL) and post-selective etching. It was found that scratches with phase differences can lead to the periodic formation of amorphous silicon (a-Si), which can resist etching. Consequentially, misaligned sine channels with thick–thin alternating 3D shapes can be generated in situ from the scratched traces after the etching. Further analysis showed that a thicker a-Si layer can be obtained by reducing the line spacing in the scratching, confirmed by Raman detections and simulations. With the proposed method, the misaligned sine micromixer was achieved with higher mixing efficiency than ever. The duplicating process was also investigated for high-precision production of micromixers. The study provided strategies for the miniaturization of high-performance microfluidic chips. [ABSTRACT FROM AUTHOR]

Cell-cell interactions are important to numerous biological systems, including tissue microenvironments, the immune system, and cancer. However, current methods for studying cell combinations and interactions are limited in scalability, allowing just hundreds to thousands of multicell assays per experiment; this limited throughput makes it difficult to characterize interactions at biologically relevant scales. Here, we describe a paradigm in cell interaction profiling that allows accurate grouping of cells and characterization of their interactions for tens to hundreds of thousands of combinations. Our approach leverages high-throughput droplet microfluidics to construct multicellular combinations in a deterministic process that allows inclusion of programmed reagent mixtures and beads. The combination droplets are compatible with common manipulation and measurement techniques, including imaging, barcode-based genomics, and sorting. We demonstrate the approach by using it to enrich for chimeric antigen receptor (CAR)-T cells that activate upon incubation with target cells, a bottleneck in the therapeutic T cell engineering pipeline. The speed and control of our approach should enable valuable cell interaction studies.

Production of high-energy lipids by microalgae may provide a sustainable energy source that can help tackle climate change. However, microalgae engineered to produce more lipids usually grow slowly, leading to reduced overall yields. Unfortunately, culture vessels used to select cells based on growth while maintaining high biomass production, such as well plates, water-in-oil droplet emulsions, and nanowell arrays, do not provide production-relevant environments that cells experience in scaled-up cultures (e.g., bioreactors or outdoor cultivation farms). As a result, strains that are developed in the laboratory may not exhibit the same beneficial phenotypic behavior when transferred to industrial production. Here, we introduce PicoShells, picoliter-scale porous hydrogel compartments, that enable >100,000 individual cells to be compartmentalized, cultured in production-relevant environments, and selected based on growth and bioproduct accumulation traits using standard flow cytometers. PicoShells consist of a hollow inner cavity where cells are encapsulated and a porous outer shell that allows for continuous solution exchange with the external environment. PicoShells allow for cell growth directly in culture environments, such as shaking flasks and bioreactors. We experimentally demonstrate that Chlorella sp., Saccharomyces cerevisiae, and Chinese hamster ovary cells, used for bioproduction, grow to significantly larger colony sizes in PicoShells than in water-in-oil droplet emulsions (P < 0.05). We also demonstrate that PicoShells containing faster dividing and growing Chlorella clonal colonies can be selected using a fluorescence-activated cell sorter and regrown. Using the PicoShell process, we select a Chlorella population that accumulates chlorophyll 8% faster than does an unselected population after a single selection cycle.

Cell-free protein synthesis can enable the combinatorial screening of many different components and concentrations. However, manual pipetting methods are unfit to handle many cell-free reactions. Here, we describe a microfluidic method that can generate hundreds of unique submicroliter scale reactions. The method is coupled with a high yield cell-free system that can be applied for broad protein screening assays.

Many cellular analytical technologies measure only the average response from a cell population with an assumption that a clonal population is homogenous. The ensemble measurement often masks the difference among individual cells that can lead to misinterpretation. The advent of microfluidic technology has revolutionized single-cell analysis through precise manipulation of liquid and compartmentalizing single cells in small volumes (pico- to nano-liter). Due to its advantages from miniaturization, microfluidic systems offer an array of capabilities to study genomics, transcriptomics, and proteomics of a large number of individual cells. In this regard, microfluidic systems have emerged as a powerful technology to uncover cellular heterogeneity and expand the depth and breadth of single-cell analysis. This review will focus on recent developments of three microfluidic compartmentalization platforms (microvalve, microwell, and microdroplets) that target single-cell analysis spanning from proteomics to genomics. We also compare and contrast these three microfluidic platforms and discuss their respective advantages and disadvantages in single-cell analysis.

Single-cell encapsulation in droplet microfluidics is commonly hindered by the tradeoff between cell suspension density and on-chip focusing performance. In this study, we introduce a novel droplet microfluidic chip to overcome this challenge. The chip comprises a double spiral focusing unit, a flow resistance-based sample enrichment module with fine-tunable outlets, and a crossflow droplet generation unit. Utilizing a low-density cell/bead suspension (2 × 106 objects/mL), cells/beads are focused into a near-equidistant linear arrangement within the double spiral microchannel. The excess water phase is diverted while cells/beads remain focused and sequentially encapsulated in individual droplets. Focusing performance was assessed through numerical simulations and experiments at three flow rates (40, 60, 80 μL/min), demonstrating successful focusing at 40 and 80 μL/min for beads and cells, respectively. In addition, both simulation and experimental results revealed that the flow resistance at the sample enrichment module is adjustable by punching different outlets, allowing over 50% of the aqueous phase to be removed. YOLOv8n-based droplet detection algorithms realized the counting of cells/beads in droplets, statistically demonstrating single-cell and bead encapsulation rates of 72.2% and 79.2%, respectively. All the results indicate that this on-chip sample enrichment approach can be further developed and employed as a critical component in single-cell encapsulation in water-in-oil droplets. [ABSTRACT FROM AUTHOR]

This paper investigates the physical layer security (PLS) performance of full-duplex cooperative non-orthogonal multiple access (FD-CNOMA) network in the presence of an external passive eavesdropper. Firstly, we derive approximate analytical expressions for the secrecy outage probabilities (SOPs) of the downlink users and the system SOP (SSOP) of a single-cell FD-CNOMA network, considering the presence/absence of direct link from the base station (BS) to the far user, under imperfect successive interference cancellation conditions. We consider both perfect channel state information and imperfect CSI conditions. To enhance the PLS performance, we propose an artificial noise (AN)-aided framework and derive approximate analytical expressions for the SOPs of the downlink users and the SSOP of the AN-aided FD-CNOMA network. The asymptotic SOP and SSOP expressions are also derived, which are used to determine the secrecy diversity orders. The proposed AN-aided framework significantly reduces the SOPs of the users and the SSOP of the network compared to that without AN. To further enhance the PLS performance, we use the Polak-Ribiere conjugate gradient method to determine the optimal power allocation coefficient (OPAC) for the users at the BS that minimizes the SSOP of the AN-aided FD-CNOMA network. The proposed OPAC significantly reduces the SOPs of the users and the SSOP, compared to random selection/equal setting of the PACs. Finally, we extend the performance evaluations to a multi-cell scenario and demonstrate that the PLS performance of the FD-CNOMA network significantly deteriorates in the presence of co-channel interference. [ABSTRACT FROM AUTHOR]

Micromixers play a crucial role as essential components in microfluidic analysis systems. This paper introduces a novel micromixer designed by harnessing electrokinetic vortices arising on the surface of a Janus droplet within a microchannel. The Janus droplet is characterized by different polarities of charges on its two sides (upstream part and downstream part). In the presence of a direct current electric field, the droplet's surface generates electroosmotic flows in opposite directions, resulting in the formation of vortices and facilitating solution mixing. Results from numerical simulations suggest that a better mixing performance of the micromixer is associated with both a higher absolute value of the zeta potential ratio between the downstream and upstream surfaces of the Janus droplet and a larger downstream surface area. Additionally, this study reveals that microchannel dimensions significantly influence the performance of the micromixer. Smaller microchannel widths and heights correspond to a larger mixing index for the micromixer. The micromixer presented in this study features a simple structure, easy fabrication, and holds promising application potential. [ABSTRACT FROM AUTHOR]

Enzyme-linked immunosorbent assays (ELISA), as one of the most used immunoassays, have been conducted ubiquitously in hospitals, research laboratories, etc. However, the conventional ELISA procedure is usually laborious, occupies bulky instruments, consumes lengthy operation time, and relies considerably on the skills of technicians, and such limitations call for innovations to develop a fully automated ELISA platform. In this paper, we have presented a system incorporating a robotic-microfluidic interface (RoMI) and a modular hybrid microfluidic chip that embeds a highly sensitive nanofibrous membrane, referred to as the Robotic ELISA, to achieve human-free sample-to-answer ELISA tests in a fully programmable and automated manner. It carries out multiple bioanalytical procedures to replace the manual steps involved in classic ELISA operations, including the pneumatically driven high-precision pipetting, efficient mixing and enrichment enabled by back-and-forth flows, washing, and integrated machine vision for colorimetric readout. The Robotic ELISA platform has achieved a low limit of detection of 0.1 ng/mL in the detection of a low sample volume (15 μL) of chloramphenicol within 20 min without human intervention, which is significantly faster than that of the conventional ELISA procedure. Benefiting from its modular design and automated operations, the Robotic ELISA platform has great potential to be deployed for a broad range of detections in various resource-limited settings or high-risk environments, where human involvement needs to be minimized while the testing timeliness, consistency, and sensitivity are all desired.

We derived equations and closed-form solutions of transit time for a viscous droplet squeezing through a small circular pore with a finite length at microscale under constant pressures. Our analyses were motivated by the vital processes of biological cells squeezing through small pores in blood vessels and sinusoids and droplets squeezing through pores in microfluidics. First, we derived ordinary differential equations (ODEs) of a droplet squeezing through a circular pore by combining Sampson flow, Poiseuille flow, and Young–Laplace equations and took into account the lubrication layer between the droplet and the pore wall. Second, for droplets wetting the wall with small surface tension, we derived the closed-form solutions of transit time. For droplets with finite surface tension, we solved the original ODEs numerically to predict the transit time. After validations against experiments and finite element simulations, we studied the effects of pressure, viscosity, pore/droplet dimensions, and surface tension on the transit time. We found that the transit time is inversely linearly proportional to pressure when the surface tension is low compared to the critical surface tension for preventing the droplet to pass and becomes nonlinear when it approaches the critical tension. Remarkably, we showed that when a fixed percentage of surface tension to critical tension is applied, the transit time is always inversely linearly proportional to pressure, and the dependence of transit time on surface tension is nonmonotonic. Our results provided a quick way of quantitative calculations of transit time for designing droplet microfluidics and understanding cells passing through constrictions. [ABSTRACT FROM AUTHOR]

Droplet-based microfluidic technology is a powerful tool for generating large numbers of monodispersed nanoliter-sized droplets for ultra-high throughput screening of molecules or single cells. Yet further progress in the development of methods for the real-time detection and measurement of passing droplets is needed for achieving fully automated systems and ultimately scalability. Existing droplet monitoring technologies are either difficult to implement by non-experts or require complex experimentation setups. Moreover, commercially available monitoring equipment is expensive and therefore limited to a few laboratories worldwide. In this work, we validated for the first time an easy-to-use, open-source Bonsai visual programming language to accurately measure in real-time droplets generated in a microfluidic device. With this method, droplets are found and characterized from bright-field images with high processing speed. We used off-the-shelf components to achieve an optical system that allows sensitive image-based, label-free, and cost-effective monitoring. As a test of its use we present the results, in terms of droplet radius, circulation speed and production frequency, of our method and compared its performance with that of the widely-used ImageJ software. Moreover, we show that similar results are obtained regardless of the degree of expertise. Finally, our goal is to provide a robust, simple to integrate, and user-friendly tool for monitoring droplets, capable of helping researchers to get started in the laboratory immediately, even without programming experience, enabling analysis and reporting of droplet data in real-time and closed-loop experiments. [ABSTRACT FROM AUTHOR]

Microfluidic-based lab-on-a-chip technology is a multidisciplinary approach, which has evolved rapidly in the past decade and remains a hot research topic as a promising microanalysis platform for a plethora of biomedical applications. Microfluidic chips have been successfully applied in cancer diagnosis and monitoring, given that they can lead to the effective separation and analysis of cancer-derived substances such as extracellular vesicles (EVs), circulating tumour cells (CTCs) and circulating DNA (ctDNA), proteins and other metabolites. In particular, EVs and CTCs are two outstanding objects for cancer liquid biopsy, which share similar membrane structures but possess different sizes. Through molecular typing and concentration detection of EVs, CTCs and ctDNA, disease-related information can be well-learned, including the development stage and prognosis of cancer. However, the conventional separation and detection methods are often time-consuming with limited efficiency. In comparison, the use of microfluidic platforms can effectively simplify the separation and enrichment process and improve the detection efficiency significantly. Although review papers have been published on the application of microfluidic chips for the analysis of objects of liquid biopsy, generally they focused on a specific detection target, lacking a descriptive extraction of the commonality of LOC devices used in liquid biopsy. Thus, few of them present a comprehensive overview and outlook on the design and application of microfluidic chips for liquid biopsy. This motivated us to prepare this review paper, which is divided into 4 parts. The first part aims to elucidate the material selection and fabrication approaches of microfluidic chips. In the second part, the important separation strategies, including physical methods and biological methods, are discussed. The third part highlights the advanced on-chip technologies for the detection of EVs, CTCs and ctDNA by providing practical examples. In the fourth part, novel on-chip applications of single cells/exosomes are introduced. Finally, the prospective outlook and challenges for the long-term development of on-chip assays are envisioned and discussed. [ABSTRACT FROM AUTHOR]

The cerebrovascular blood vessels feed necessary agents such as oxygen, glucose, and so forth. to the brain which maintains the smooth functioning of the human body. However, the blood–brain barrier as a vascular border restricts the entry of drugs that can be necessary for the treatment of neurological disorders. The fluid shear stress in the cerebrovascular blood vessels may regulate the drug delivery in the interface between the cerebrovascular blood vessels and the brain. The intensity of influence by various factors that affects the shear stress in the cerebrovascular blood vessels is scarcely addressed in the present study. A hybrid approach of computational fluid dynamics and Taguchi analysis is proposed to evaluate the influence of various geometrical and operating factors on the shear stress in the microfluidic cerebrovascular channel. Furthermore, the non‐Newtonian behavior of blood flow is considered to evaluate the shear stress in the microfluidic cerebrovascular channel. The Newtonian and six non‐Newtonian fluids models of Carreau, Carreau–Yasuda, Casson, Cross, Ostwald–de Waele, and Herschel–Bulkley are numerically tested under various conditions of the flow rate, width, and height of the channel to find the viscosity influence on the shear stress. The Taguchi analysis consisting of range and variance analyses is applied to the L16 orthogonal array to evaluate the effect of various factors on shear stress in terms of influence order, range, F value, and percentage contribution. The parameters for the considered six non‐Newtonian fluid models are proposed to accurately map the viscosity behavior with shear strain compared to the actual blood flow behavior. The Newtonian, Carreau, and Carreau–Yasuda non‐Newtonian fluid models are found accurately with maximum errors between the experimental and numerical shear stress results as 2.17%, 1.30%, and 1.48%, respectively. The shear stress decreases with an increase in the width and height of the channel and a decrease in the viscosity for all flow rates. The porosity is evaluated as a highly influential factor followed by the flow rate, width, and height of the channel in decreasing order based on their effects on the shear stress. The modified shear stress equation is proposed with an accuracy of 0.96 by integrating the effect of porosity in addition to width, height, flow rate, and viscosity. The in‐vitro microfluidic cerebrovascular model could be designed and manufactured based on the proposed results on influence order, F value, and percentage contribution of various factors in direction of achieving the in‐vivo level shear stress. [ABSTRACT FROM AUTHOR]

In the process of tertiary migration of crude oil, the phase that occurs after the cessation of primary exploitation of petroleum fluid deposits, the deposit is characterized by a state of maximum discontinuity of microscale phases and their abnormal gravitational positioning. This is precisely why it is necessary to discuss the blocking/unblocking mechanisms of wetting phase and non-wetting phase plugs in/out of capillary microtraps. The article presents for the first time a microfluidic behavior of crude oil through cores, with the analysis of polymer flow through rock pores and their filling with petroleum fluids. [ABSTRACT FROM AUTHOR]

The present study is focused on micromixing enhancement techniques for electroosmotic flows in a modulated microchannel with a modified topology by utilizing heated blocks on the surface of the microchannel. The heated blocks carry higher temperatures as compared to the other portions of the channel wall, resulting in a sharp variation in the temperature of the fluid. The species transport is governed by the Nernst–Planck equation in a modified form by adding a thermo-electrochemical migration term due to the temperature variation in the ions, justifying the electrochemical equilibrium conditions. The fluid considered for the study is non-Newtonian and is governed by a power-law model. The Navier–Stokes equations, along with the thermal energy equation, are simulated numerically in a coupled form utilizing a finite volume-based semi-implicit method for the pressure-linked equation algorithm to interpret the behavior of the electric potential distribution, the external electric field, the flow field, the temperature distribution, and the species concentration, which are the major contributors for the mixing efficiency. The numerically simulated results are varied with the analytical results for the simple electroosmotic flow in the microchannel, indicating that the mixing efficiency can be enhanced by increasing the temperature of the heated blocks. Due to the thermo-electrochemical migration, ions are redistributed along the heated blocks, oscillating the flow velocity by creating vortices, resulting in the mixing enhancement. The effects of the geometrical parameters, the Debye–Hückel parameter, the temperature gradient, the power-law index, and the Nusselt number are elaborated for the effective flow rate and micromixing. The mixing efficiency is found to be optimum for higher temperature gradients and higher power-law indices. The net throughput analysis that combines the geometrical modulation and wall temperature variation will aid in improving the design and fabrication of microfluidic mixers. [ABSTRACT FROM AUTHOR]

A Hele–Shaw quadratic flow in the form of a six-port microfluidic device is employed to study the deformation of a single channel-spanning or Hele–Shaw Newtonian drop suspended in a Newtonian medium. An initially circular drop in a quadratic flow deforms into a regular triarcle, i.e., a rounded-corner triangle. Theoretically, the deformation is calculated in the limit of small capillary number, which is defined as C a = C μ a 4 / (4 γ b 2) , where C is the quadratic flow rate, μ is the suspending fluid viscosity, a is the drop radius, γ is the interfacial tension, and b is the channel depth. The theory matches reasonably well with the experiment for small capillary numbers. This is the new way of deforming drops on a Hele–Shaw quadratic platform experimentally and may lead to measurements such as complex interfacial properties and breakup. [ABSTRACT FROM AUTHOR]

In recent times, among all the substrates used in microfluidic systems, cellulose paper is used as a handy, low-cost substrate that has gained attention for carrying fluid on its surface over capillary pressure. Cellulose paper substrate has exhibited great potential on microfluidic devices owing to prevalent obtainability, easy fluid (sample) flow system, flexibility, and low cost. Cellulose paper is fibrous, biocompatible, and hydrophilic in nature due to the hydroxyl group of the cellulose molecule. Based on the dominance of functional hydroxyl groups, cellulose is very reactive and every single cellulose fiber acts like a microchannel on the paper substrates. Aggregation of inter- and intra-cellulose fiber chains has a strong binding affinity to it and toward materials containing hydroxyls groups. In this paper, impact of inter- and intra-cellulose fiber on the paper substrate has been discussed through an experimental study. For the addition of work a "hydrophobic penetration-on-paper substrate (Hyp-POP)" method has been shown by using TiO2 ink as a hydrophobic material to design the microfluidic channel on the Whatman cellulose filter paper (grade 1) as a paper substrate. In this experimental study, the intra-cellulose fibers of paper substrate interact through hydrogen bonds with water molecules and form a hydrophilic surface on paper substrate while TiO2 binds with intra-cellulose fibers by electrostatic forces which change the crystallinity of intra-cellulose fiber and make the surface of paper substrate; hydrophobic. Field Emission Scanning Electron Microscope (FESEM) analysis is conceded for microfluidic channel analysis on the paper surface and EDS is carried out for TiO2 ink contents analysis. It has been experimentally observed that the printing material of TiO2 ink with 17.2% Ti content is suitable to integrate hydrophobic barrier on paper substrate for microfluidic channel fabrication. The wetting ability of Whatman cellulose filter paper (grade 1) was further evaluated by contact angle measurements (Data physics OCA 15EC). Using "Hyp-POP" method a hydrophobic pattern (width 3140 μ m) on paper substrate has been made for the flow of liquid (blue fountain ink) into a paper fluidic channel (width 1860 μ m) without any leakage. [ABSTRACT FROM AUTHOR]