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Controllable manipulation of fluid flow is crucial for efficient particle separation, which is associated with plenty of biomedical and industrial applications. Microfluidic technologies have achieved promising progress in particle positioning depending on inertial force with or without the help of the Dean effect. Herein, we describe an inertial microfluidic system containing a spiral microchannel for various highly efficient particle separations. We demonstrated that Dean-like secondary flow can be regulated by geometric confinement in the microchannel. On the introduction of a library of micro-obstacles into the spiral microchannels, the resulting linear acceleration of secondary flow can be applied to remarkably enhance particle focusing in time and space. Further, multiple separating and sorting manipulations of particles including polymeric particles, circulating tumor cells, and blood cells, can be successfully accomplished in the dimension-confined spiral channels in a sheathless, high-throughput (typically 3 ml min−1), long-term (at least 4 h), and highly-efficient (up to 99.8% focusing) manner. The methodological achievement pointing to ease-of-use, effective, and high-throughput particle manipulations is useful for both laboratory and commercial developments of microfluidic systems in life and material sciences. [ABSTRACT FROM AUTHOR]

Cell sorting by filtration techniques offers a label-free approach for cell separation on the basis of size and deformability. However, filtration is always limited by the unpredictable variation of the filter hydrodynamic resistance due to cell accumulation and clogging in the microstructures. In this study, we present a new integrated microfluidic device for cell separation based on the cell size and deformability by combining the microstructure-constricted filtration and pneumatic microvalves. Using this device, the cell populations sorted by the microstructures can be easily released in real time for subsequent analysis. Moreover, the periodical sort and release of cells greatly avoided cell accumulation and clogging and improved the selectivity. Separation of cancer cells (MCF-7, MDA-MB-231 and MDA231-LM2) with different deformability showed that the mixture of the less flexible cells (MCF-7) and the flexible cells (MDA-MB-231 and MDA231-LM2) can be well separated with more than 75% purity. Moreover, the device can be used to separate cancer cells from the blood samples with more than 90% cell recovery and more than 80% purity. Compared with the current filtration methods, the device provides a new approach for cancer cell separation with high collection recovery and purity, and also, possesses practical potential to be applied as a sample preparation platform for fundamental studies and clinical applications. [ABSTRACT FROM AUTHOR]

Micropatterning technologies are emerging as an enabling tool for various microfluidic-based applications in life sciences. However, the high throughput and multiplex localization of multiple bio-components in a microfluidic device has not yet been well established. In this paper, we describe a simple and in situ micropatterning method using an integrated microfluidic device with pneumatic microstructures (PμSs) for highly controllable immobilization of both proteins and cells in a high throughput, geometry-dynamic, and multi-patterning way. The precise Pluronic F127 passivation of a microchamber surface except the PμS-blocked regions was performed and characterized, and the spatial dynamics and consistency of both the PμSs and protein/cell micropatterning were optically evaluated and quantitatively demonstrated too. Furthermore, a systematic investigation of PμS-assisted micropatterning in microfluidics was carried out. The feature of high throughput and spatial control of micropatterning can be simply realized by using the well-designed PμS arrays. Meanwhile, the co-micropatterning of different proteins (bovine serum albumin and chicken egg albumin) and cells (human umbilical vein endothelial cells and human hepatocellular carcinoma cells) in a microfluidic device was successfully accomplished with the orderly serial manipulation of PμS groups. We demonstrate that PμS-assisted micropatterning can be applied as a convenient microfluidic component for large-scale and diversified protein/cell patterning and manipulation, which could be useful for cell-based tissue organization, high-throughput imaging, protein-related interactions and immunoassays. [ABSTRACT FROM AUTHOR]

The supramolecular interaction between the host molecule β-cyclodextrin (β-CD) and the guest molecule adamantane is extensively applied in several disciplines. However, recent studies on the applications of this molecular recognition mainly focused on glass, silicon, and gold substrates. Few studies have explored the field of poly(dimethylsiloxane) (PDMS), an optically transparent elastomer widely used in biological microfluidic devices. In the present study, various functional group-modified adamantyl-terminated dendronized molecules were synthesized via an efficient and facile route. The binding of adamantyl-terminated dendronized molecules onto β-CD-conjugated PDMS surfaces and their reversible dissociation from PDMS surfaces through the competitive mechanism of β-CD-N3 were studied. The results showed that the dissociation is relatively slow compared with the binding, and the former process can be accelerated through exchanging the original β-CD-N3 solution with a fresh one. Afterward, more complex multilayer assemblies were constructed on PDMS surfaces using the host–guest interaction between adamantane and β-CD as well as between biotin and streptavidin. A further study on the association and dissociation of the established multilayer assemblies showed that the assembly constructed with a biotinylated monoadamantyl-terminated molecule has a reversible property, whereas that with a biotinylated triadamantyl-terminated molecule has an irreversible property. These results demonstrated that the reversible properties of the fabricated assembly can be easily modulated on the PDMS surfaces by regulating the valence of the supramolecular interaction between adamantane and β-CD. [ABSTRACT FROM AUTHOR]

A microfluidic approach for the integration of multiple biochemical concentration gradients in a single microfluidic device is presented in article number 1800434, by Wenming Liu, Jinyi Wang, and co‐workers. The employment of multidirectional hydrogel barriers permits a facile, stable, and long‐term microfluidic production of shear‐free single and double biochemical gradients. Multi‐gradient microfluidics provides a prototypical platform to perform on‐chip biomimetic neuronal manipulation and analysis for the exploration of neurogenesis and development as well as neuro‐regeneration. [ABSTRACT FROM AUTHOR]

Three-dimensional tumor culture methods offer a high degree of biological and clinical relevance to in vitro models as well as cancer therapy. However, a straightforward, dynamic, and high-throughput method for micro-manipulation of 3D tumors is not yet well established. In this study, we present a novel and simple strategy for producing biomimetic 3D tumors in a controllable, high throughput manner based on an integrated microfluidic system with well-established pneumatic microstructures. Serial manipulations, including one-step cell localization, array-like self-assembly, and real-time analysis of 3D tumors, are accomplished smoothly in the microfluidic device. The recovery of tumor products from the chip is performed by dynamic off-switch of the pneumatic microstructures. In addition, this microfluidic platform is demonstrated to be capable of producing multiple types of 3D tumors and performing the evaluation of tumor targeting by nanomedicine. The pneumatic microfluidic-based 3D tumor production shows potential for research on tumor biology, tissue engineering, and drug delivery. [ABSTRACT FROM AUTHOR]

• A microfluidic system for simultaneous and large scale multi-size 3D tumor manipulation and analysis was developed. • Controllable and massive production of biomimetic multi-size tumors was established in the single microfluidic device. • The system allows highly efficient multi-size tumor formation with quantitative-uniformity. • Orthogonal drug resistance determination of multi-size tumors was accomplished in throughput in the single device. The establishment of a miniaturized platform capable of microscale control for sequential, coordinated, and throughput biomimetic tumor manipulation and analysis offer a high degree of biological and clinical relevance to cancer therapy and pharmaceutical research. In this study, we developed a microfluidic system with well-established microwell arrays and simple double-layer composition that allows massive fabrication of biomimetic multi-size 3D tumors and their simultaneous manipulation and orthogonal analysis. Serial manipulations including cell localization, array-like self-assembly/cultivation, and dynamic analysis of different types of 3D tumors, were accomplished in the microfluidic device. We demonstrated that the microfluidic platform is stable and throughput cell trapping and tumor generation with quantity uniform. Furthermore, on-chip monitoring and throughput analysis of tumor phenotypes and responses to culture and different chemotherapies were also achieved in the device. The microfluidic advancement offers a new methodological approach for the development of high-performance and multifunctional 3D tumor systems and for tissue-mimicking cancer research and therapy evaluation. This microfluidic platform, which has the capability of multiple control in time and space, holds great potential for applications in the fields of tumor biology, tissue engineering, and clinical medicine. [ABSTRACT FROM AUTHOR]

[Display omitted] • A thread-based microfluidic device with a NiS/GO modified carbon paste electrode was developed. • Low-cost and continuous method for urea electrochemical detection. • Urea detection in samples of artificial and natural saliva. Urea concentration is an essential indicator of various kidney diseases. The development of an effective method for detecting urea is still an important task. In recent years, microfluidic devices have become an attractive approach for constructing a novel urea analysis system because of their advantages such as less reagent and low sample consumption and high analysis speed. In this report, a cotton thread-based microfluidic electrochemical analysis device was developed for flow urea detection by 3D printing technology. Cotton thread was used as the microfluidic channel for sample flow and NiS/GO modified carbon paste electrode was worked as a urea sensor. The experimental results showed that the proposed microfluidic device provided a stable carrier fluid flow rate and a significant catalytic performance for the electrochemical oxidation of urea. The device allowed to detect urea in the concentration range from 0.1 mM to 6.0 mM with a detection sensitivity of 32.61 μA L mmol−1. In addition, the proposed method has been successfully applied to the detection of urea in human saliva samples by a non-enzymatic amperometry method. More importantly, the approach can be successfully applied to non-enzymatic amperometric detection of urea in human saliva samples. [ABSTRACT FROM AUTHOR]

A novel, facile, and flexible approach for the easy assembly of microfluidic droplet devices using commercially available components is presented. Three different types of devices have been designed and tested, and the experimental results indicated that the devices offer a promising platform for the controllable generation of highly monodisperse droplets with sizes in the micrometer to millimeter diameter ranges. The advantages of the devices include their low cost, portability, reusability, high accuracy, and reliability. Most importantly, the simple and reversible combination of the different components allows the flexible design of versatile devices for fabricating multiple droplets with diverse structures. Therefore, the devices constitute a powerful microplatform that can be used for scientific and industrial applications. [ABSTRACT FROM AUTHOR]

Large-scale single-cell arrays are urgently required for current high-throughput screening of cell function and heterogeneity. However, the rapid and convenient generation of large-scale single-cell array in a multiplex and universal manner is not yet well established. In this paper, we report a simple and reliable method for the generation of a single-cell array by combining pneumatic microvalve arrays (PμVAs) and hydrodynamic single-cell trapping sites in a single microfluidic device. The PμVAs, which can be precisely controlled by actuated pressures, were designed to guide multiple types of cells being trapped in the corresponding single-cell trapping sites located in the fluidic channel. According to the theoretical demonstration and computational simulation, we successfully realized a multiplex single-cell array with three different types of cells by a step-by-step protocol. Furthermore, the analysis of cellular esterase heterogeneity of the three types of cells was concurrently implemented in the device as a proof-of-concept experiment. All the results demonstrated that the method developed in the current study could be applied for the generation of large-scale single-cell array with multiple cell types, which would be also promising and helpful for single-cell-based high-throughput drug test, multipurpose immunosensor and clinical diagnosis. [ABSTRACT FROM AUTHOR]

Abstract: The current paper reports the synthesis of a highly hydrophilic, antifouling dendronized poly(3,4,5-tris(2-(2-(2-hydroxylethoxy)ethoxy)ethoxy)benzyl methacrylate) (PolyPEG) brush using surface initiated atom transfer radical polymerization (SI-ATRP) on PDMS substrates. The PDMS substrates were first oxidized in H2SO4/H2O2 solution to transform the Si–CH3 groups on their surfaces into Si–OH groups. Subsequently, a surface initiator for ATRP was immobilized onto the PDMS surface, and PolyPEG was finally grafted onto the PDMS surface via copper-mediated ATRP. Various characterization techniques, including contact angle measurements, attenuated total reflection infrared spectroscopy, and X-ray photoelectron spectroscopy, were used to ascertain the successful grafting of the PolyPEG brush onto the PDMS surface. Furthermore, the wettability and stability of the PDMS–PolyPEG surface were examined by contact angle measurements. Anti-adhesion properties were investigated via protein adsorption, as well as bacterial and cell adhesion studies. The results suggest that the PDMS–PolyPEG surface exhibited durable wettability and stability, as well as significantly anti-adhesion properties, compared with native PDMS surfaces. Additionally, our results present possible uses for the PDMS–PolyPEG surface as adhesion barriers and anti-fouling or functional surfaces in biomedical applications. [Copyright &y& Elsevier]

Abstract: This work describes chemical heat shock transformation of foreign plasmid DNA into bacterial host Escherichia coli cells using a capillary-composited microfluidic device. Transformation processes of the loading, mixing, heat shock and recovery of the transformation mixture were carried out automatically in a linear fashion. In addition, by utilizing the capillary with a hollow cylindrical chamber as heating source, simple, low cost local heat shock with accurate heat shock time to transformation mixture was obtained on the microdevice. Results demonstrated that plasmid DNA could be effectively transformed into E. coli, and the transformation efficiency and frequency were as the same level or better than conventional tube-based method. This work complements other microfluidic technologies for potential gene cloning and functional genomics studies. [Copyright &y& Elsevier]

Tetrathiafulvalene (TTF) based charge-transfer compounds are ideal as a transducer layer for a solid-contact ion-selective electrode (SC-ISE), because of their excellent ionic conductivity and high capacitance. Since nanomaterials with tailored geometries exhibit unique shape-dependent properties and subsequent utilization of them for the fabrication of electrochemical devices is of significant interest. Gold-TTF (Au-TTF) with different morphologies such as flower-like, sheet-like, long wire and tubular with different length, were synthesized by microfluidics-dictated synthesis in a fast, simple and continuous procedure. The electrochemical performance of synthesized Au-TTF hybrid crystals was characterized by cyclic voltammetric, electrochemical impedance and constant-current chronopotentiometric measurement. The results demonstrate that long-tubular-like Au-TTF crystal is best suitable for ISE due to its great stability, high capacitance and co-existence of TTF/TTF+ providing a stable interphase potential. Then paper-based potentiometric potassium sensors were fabricated based on flower-like and long-tubular-like Au-TTF hybrid crystal as transducer layer of ISE and reference electrode. Compared to paper-based sensor with flower-like Au-TTF as transducer layer, paper-based sensor with long-tubular-like Au-TTF as transducer layer exhibits a much better Nernstian response with a slop of 57.64 ± 0.09 mV/dec and a lower detection limit of 2.75 × 10−6 M. Furthermore, the fabricated potentiometric sensor requires only 5 μL samples to test and displays little water-layer, good anti-interference, and great reproducibility and selectivity. [ABSTRACT FROM AUTHOR]