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The review presents the classification of point-of-care (POC) devices, and discusses the main characteristics of the devices and the requirements for them. The differences between the POC testing method and the laboratory method of analysis are considered. Examples of devices that fit the definition of POC for diagnosing infectious diseases are given.

A quantitative polymerase chain reaction in real time (real time PCR) has been implemented on polymer microfluidic devices made of polycarbonate and polypropylene. The threshold cycle is determined based on the inflection point of the first-order logistic growth function, which reliably approximates the PCR curve in the absence of interfering factors, for example, the presence of bubbles in the reaction chamber. Use of statistical criteria (generalized Student's criterion, one-way analysis of variance) revealed the insignificance of the influence of the polymer type on the estimation of the position of the threshold cycle in terms of the previously selected algorithm for its search. When using an alternative algorithm for finding the threshold cycle based on the plotting of a tangent to the kinetic curve, in some cases there is a significant influence of the polymer type on the estimation of the position of the threshold cycle and, as a consequence, on the result of quantitative analysis. Proposed and discussed are algorithms for detecting bubbles in the reaction chamber based on the detection of a discrepancy in the measurement sequence associated with both estimates of the approximating dependence's parameters and the characteristics of the time series formed by approximation errors.

Based on qualitative and quantitative criteria, solvents compatible with polymethyl methacrylate (PMMA) such as ethyl acrylate, n-butylacrylate, and vinyl acetate were selected. Features of the solvent-bonded seam of non-detachable bonding of PMMA of various grades obtained using the selected solvents were investigated. It is shown that the method of chemical solvent bonding with vinyl acetate can be an alternative to gluing in sealing of microchips, since the solvent-bonded seam makes a smaller contribution to the change in the working volume of microstructures than the glue seam.

Chemically synthesized inorganic lead halide perovskite lasers based on nanostructures, generating coherent light at room temperature, and having a low threshold, have become powerful tools for var...

A technique for nondestructive determination of the thickness of the adhesive layer of microchips made of polymethyl methacrylate (PMMA) has been proposed and tested based on the estimation of the volume of adhesive introduced into the gap between the plates. It is shown that the thickness of the adhesive layer indirectly depends on the features of the technology for producing PMMA sheets and the formation of microstructures in it.

A number of methods for analyzing liquid media are based on carrying out specific reactions with the component to be determined. In microfluidic devices, due to the laminarity of the flow, it is difficult to organize uniform mixing of the reaction components, which deteriorates the reproducibility of the results of the reactions and the quality of the analysis. To improve the efficiency of passive mixing in microfluidic systems, you can use the input channel samples of variable geometry, in particular, with bends, or with a variable width. The mixing efficiency is directly related to the variability of reagent concentrations in the working area, and this characteristic is adequately evaluated through the dispersion of the concentration profile. To obtain an estimate of the dispersion of the concentration distribution, an analytical solution of the convective–diffusion equation using the method of moments is proposed. For this, the sample entry system—a straight section of constant width with an additional linearly expanding channel—is approximately replaced by an equivalent channel of constant width. Also, the values of convective velocity and diffusion coefficient are approximately replaced by averaged ones. The dispersion estimates obtained on the basis of an approximate analytical solution have an acceptable agreement with the results of numerical 2D modeling of convective mass transfer in COMSOL MULTYPHYSICS.

Microchip devices made of glass, silicon, polymeric materials have been designed and tested for use in Point-of- Care diagnostic systems for biomedical purposes.

Recently, nanomaterials demonstrating optical response under illumination, the so-called optically responsive nanoparticles (NPs), have found their broad application as optical switchers, gas adsorbents, data storage devices, and optical and biological sensors. Unique optical properties of such nanomaterials are strongly related to their chemical composition, geometrical parameters and morphology. Microfluidic approaches for NPs’ synthesis allow overcoming the known critical stages in conventional synthesis of NPs due to a high rate of heat/mass transfer and precise regulation of synthesis conditions, which results in reproducible synthesis outcomes with the desired physico-chemical properties. Here, we review the recent advances in microfluidic approach for synthesis of optically responsive nanomaterials (plasmonic, photoluminescent, shape-changeable NPs), highlighting the general background of microfluidics, common considerations in the design of microfluidic chips (MFCs), and theoretical models of the NPs’ formation mechanisms. Comparative analysis of microfluidic synthesis with conventional synthesis methods is provided further, along with the recent applications of optically responsive NPs in nano- and biophotonics.

Nowadays nanofluidic devices have a great potential in biosensing and DNA sequencing applications. This work is aimed at development of the technique for fabrication of arrays of nanochannels in silicon-glass chips by focused ion beam milling. The use of lithography with charged particles (electrons and ions) paves the way for the fabrication of micro- and nanochannels and pores as well as functional nanostructures of a more complex shape in nanofluidic devices. In this study, a technique for fabrication of microfluidic chips with a system of nanochannels connecting two independent volumes (2 half cells) was developed. It was shown experimentally that the focused ion beam etching time has an influence on both the width of the created nanochannels and their depth. We suggested using anodic bonding of a silicon wafer with the net of micro- and nanochannels with a glass plate for encapsulation of such devices that provide their long lifetime of microfluidic devices. To determine the functionality of the produced devices we studied the ionic conductivity of the produced nanochannels experimentally and using a theoretical approach. Analyzing the results, we determined the effective diameter of the nanochannels and the surface charge density inside the channel which were 20 nm and 1.5 mC/m $${}^2$$ , respectively. The proposed technique allows to create ensembles of channels with a predefined width and depth. Such systems can find wide application in studies of the transport phenomena of both ions and various molecules in nanofluidic devices.

Early detection of pollutants in wastewater, water coming out of treatment facilities, drinking water, and water for agricultural needs is a challenging problem. Effective water quality monitoring requires development of new methods for express detection of pollutants. Enzymes from bioluminescent bacteria can be used for the development of new express enzyme-based bioassay systems. This work demonstrates, for the first time, a microfluidic chip to generate emulsion droplets containing two enzymes of the bacterial bioluminescent system (luciferase and NAD(P)H:FMN-oxidoreductase) with reaction substrates. The developed chip generated “water-in-oil” emulsion droplets with a volume of 0.1 μL and a frequency of up to 12 droplets per second. A portable photomultiplier tube (PMT) was used to measure the bioluminescent signal in each individual droplet; the signal-to-noise ratio was 3000/1. The intensity of luminescence in droplets depended on the concentration of copper ions. The limit of detection (LOD) for copper sulfate was 1 mg/L. We showed that bioluminescent enzymatic reactions can be carried out in droplet reactors that can be applied for online monitoring of water quality. Thus, the suggested method of biological measurements has a good perspective for biosensing in general.

Microfluidics is a promising technique for controllable synthesis of nanostructured materials that allows to conduct an experimental procedure at ambient conditions and, more importantly, enables faster synthesis process. Moreover, manipulation of the flows in the channels of microfluidic chips allows controlling the reagent's ratio, which leads to precise synthesis of nanostructures of different morphology. In the present work polydimethylsiloxane (PDMS) microfluidic chips were developed in order to control synthesis of lead cesium bromide (CsPbBr3) perovskite microcrystals by varying flow rates of reagents in microchannels. The optical properties of the obtained perovskite microparticles were characterized. Our data reveal that microfluidics enables to tune morphology of perovskite microstructures by changing the external conditions of flows.

Monodisperse polymeric particles have great potential in biomedical and physical applications. Modern high-throughput droplet microfluidic technologies make it possible to produce monodisperse water-in-oil macroemulsions with desired properties. Polymerization in a macroemulsion transforms it to a suspension of microparticles. These particles may be viewed as containers for targeted delivery of drugs and also as bioink for 3D printing of tissues and organs. Conditions for formation of PEGDA and polyacrylamide particles using a microfluidic flow-focusing emulsion generator have been studied. Manufactured microparticles have been characterized by their geometrical sizes and mechanical properties. In addition, the diffusion escape of small molecules from microparticles has been studied using Rhodamine B fluorescent dye.

Conventional chemical synthesis methods for nanomaterials fabrication do not always provide precise reproducible synthesis with controllable physicochemical parameters. A better control over the resultant properties of nanomaterials can be achieved by scaling down the synthesis approach to the microlevel. This can be realized by means of microfluidics. In this work, a microfluidic approach is applied for the controllable synthesis of perovskite particles with defined cubic morphology. The structural characterization of perovskite particles is performed using scanning electron microscopy and X-ray diffraction. All the synthesized particles demonstrate photoluminescence.

We developed a technique for fabrication microfluidic silicon-glass chips with a system of nanochannels connecting two microchannel using traditional optical lithography and a focused ion beam. To investigate the transport phenomena in the nanochannels we experimentally studied their ion conductivity and using optical microscopy confirmed the existence of the diffusion flow through them. The developed method allows us to create systems of nanochannels with on-purpose geometry and controlled sizes. Devices with such nanochannels can be applied in the creation of biosensor devices and for genetic studies.

Parameters for sample introduction, dried reagents dissolution and mixing with sample for bienzyme system NAD(H):FMN-oxidoreductase and luciferase immobilised in microfluidic chip were successfully determined. Numerical simulations of reaction chamber geometry, flavin mononucleotide (FMN) escape from starch gel and mixing options were conducted to achieve higher sensitivity of bioluminescent reaction. Results of numerical simulations were verified experimentally. The active mixer for dried reagents was made from an electro-mechanical speaker's membrane which was connected to the input of the chip. Such a mixer provided better efficiency than a passive mixing, and it is simple enough for use in point-of-care devices with any systems based on immobilised enzymes in chips.

Technologies and methods of prototyping microfluidic devices are widely used in solving many biological problems and testing of operability of new microanalytic systems. This study is devoted to analyzing the features of the formation of microstructures in SU-8 photoresist and the preparation of replicas in polydimethyl siloxane by the soft lithography method. It has been shown that the aspect ratio of the resultant microstructures is determined by their shape, size, and the force of resist adhesion to the silicon substrate and the efficiency of the circulation of the developer around microstructures. In the replication of complex microstructures, an aspect ratio of ~25 is attained. The technology considered here is used to prepare microfluidic chips with mechanical traps for fixation and the in vitro analysis of living cells.

Numerical simulation of the formation of a chemoattractant gradient in reaction chambers of a chip having different geometries enabled the determination of a structure suitable for the study of cell migration, in accordance with which hybrid polymer–glass microfluidic devices were manufactured. Verification of the procedures of alignment of cells in the reaction chamber of the chip by centrifugal force and subsequent culturing of the cells showed that microfluidic chips can be used to study cell migration under the effect of the chemoattractant gradient in vitro.

Organic-inorganic lead halide perovskites are the class of materials with unique physical properties that have attracted an interest in scientific and industrial communities. With microfluidic devices it is possible to obtain high-quality nanoparticles (NPs) based on perovskites of different physico-chemical properties such as size, shape, chemical composition. The aim of this work is to achieve the stable and reproducible synthesis of perovskite NPs on the microfluidic device. To obtain perovskite NPs two microfluidic chips (MFCs) of different topologies are investigated, where a porous membrane is introduced into MFCs using different methods: first method includes direct incorporation of commercial membrane into straight channel of MFC resulting in a "sandwich" structure, the second method implied membrane preparation as a part of a chip fabrication process. The results revealed that microfluidic devices allow synthesis of monodisperse perovskite NPs.

The current state and prospects for the use of microfluidic devices in the detection of nucleic acids at biological and medical research are discussed in the article. The main trends in the development of analytical instruments base a microfluidic platform are indicated. The most usually used technologies for the formation of micro- and nanoscale functional structures in microfluidic devices are noted. Popular materials used for the mass production of devices are highlighted. Examples of domestic developments of microfluidic devices for biological and medical research are given and perspective directions of their application are discussed.

The results on making a microfluidic chip for in vitro microscopic investigations of single cells are presented. Numerical simulation of the motion trajectories of microparticles makes it possible to determine the geometry of hydrodynamic traps, their number, and the trap arrangement in a reaction chamber. According to the developed design, microfluidic chips were fabricated from a SU-8 photoresist by photolithography. The microfluidic chips have been tested to prove their operating capacity for isolating and holding K562 human myeloid leukemia cells from a sample flow and their subsequent investigation by confocal laser scanning microscopy.

Nonmonotonic calibration dependence has been found during the fluorescent detection when performing the competitive immune analysis of insulin in a microfluidic device with the integrated sensor element based on silicate porous glass. A possible version of the interpretation of the observed effect has been discussed. The effect of the light flux intensity of the source radiation on the fluorescence of the sensor element has been studied experimentally.

Here we discuss the concepts of “biological quantity” and “nominal property” within the framework of the problem of biological measurements based on new specific results of biological analysis using a microfluidic platform and chips developed by our team earlier. It was shown that based on different microfluidic platforms it is possible to develop chips with a polyenzymatic bioluminescent system NAD(P)H:FMN-oxidoreductase-luciferase (Red + Luc), which can be used in various areas of biological analysis. Thus, disposable microfluidic chips with Red + Luc system suitable for field and indoor use were developed using continuous flow microfluidic platform. The use of droplet-based microfluidic platform allowed to develop microfluidic chips with Red + Luc system for long-term continuous measurements of water samples, for example, in places of waste disposal by industrial enterprises. The reference for comparing different biological quantities with each other in the proposed system was a photodetector, which converted non-numeric values and nominal properties recorded by a biological module Red + Luc into numerical variables. Such a reference was implemented as a portable luminometer based on silicon photomultiplier. The results allow to perform other biological measurements and to start the discussion of modern biological concepts in the language of biological measures.

Heart problems tend to occupy a leading position among elderly diseases. Organ-on-a-chip is suitable technology for researches of human body mechanisms without animal models. One of the widely spread diseases is valve calcification. To study growth of hydroxyapatite crystals a microfluidic device was created. For simulating the heart valve on microfluidic device COMSOL Multiphysics® was used. The device was fabricated from polydimethylsiloxan using spin-coating method for membrane which acts as a valve and soft lithography for the other parts.

In present work we have designed and fabricated microfluidic chips (MFC) with integrated nets of nanochannels and whisker nanostructures in microchannels for investigation of biological samples in their native environment. We have designed a number of MFC topologies: (a) hydrodynamic traps with nanoscale channels which link microchannels; (b) a structure with regular vertical nanorod (nanowhisker) array, which could be used as a sensitive element. These topologies were created by means of ion and electron beam assisted techniques. These MFCs allow to investigate biological objects by means of high resolution microscopy. Fabricated MFCs were investigated with emulator of biological objects in different buffer solutions.

The morphology of platinum films deposited onto a polymer membrane material of the Nafion type has been studied. The films with thicknesses above ∼20 nm exhibit a specific structure (morphology) that is related to the process of self-organization. The observed phenomenon is interpreted and it is established that the main mechanism responsible for the self-organization is related to the dipole interaction between clusters of the deposited catalytic metal.

This paper presents the results of measurements of the spectral characteristics of samples of porous and two-phase glasses in transmitted and reflected light. The spectral ranges in which Rayleigh scattering predominates are determined for samples of porous glasses. Estimates of the absorption coefficient and refractive index are obtained for weakly absorbing and scattering samples. The porosity and the size of the porous structures are estimated in the effective-medium model. Estimates obtained from the Gurevich-Kubelka-Munk formula are used for scattering porous glasses.

Microchannels in polyimide (PI) have been produced by means of laser ablation (LA). The obtained results confirm the possibility of using the LA technology for the functional structure formation on PI-based microfluidic chips (MFCs). The shape of the channel edge may depend on the thermal properties of PI. This circumstance makes it possible to optimize the process of MFC fabrication by selecting a proper PI and the corresponding LA regime. Optimization of the other characteristics, such as mechanical properties and planarity of the MFCs, requires additional investigations.

State-of-the-art microfluidic analytical systems are briefly surveyed. Attention is focused on the use of microchip capillary electrophoresis. The main results obtained in the development of a prototype analytical system with a laser-induced fluorescence detector for electrophoresis on a glass microfluidic chip are presented. Experimental data on electroosmotic flow and the distribution of sample fluorescence intensity over the cross section of a microchannel are analyzed. A procedure for the rapid analysis of oligonucleotides on a microfluidic chip is described.