Fluidic Devices Research Articles

Sensitive fluorometric determination of gold in geological samples using fire assay pre-concentration coupled with microfluidic paper-based analytical device

The present study was conducted to develop a simple, low-cost and sensitive micro fluidic paper-based analytical device (µPAD) for analysis of gold in geological samples. This µPAD was fabricated employing eyeliner pencil method. It consists of different zones, including detection, pH adjustment, reaction and elution. We injected 29 µL elution solution in the center of µPAD, direct Au3+, after adjusting pH, to make it react with rhodamine B. The formation of RB-Au3+ complex led to quench of rhodamine B fluorescence. The image of each detection zone was captured using a cell phone camera under a UV lamp, and luminosity intensity was subsequently measured with Photoshop software. Various parameters were studied in order to achieve the most efficient performance of the paper sensor. Under the optimized condition, a wide linear range (1–40 mg L−1, R2 = 0.996) was obtained with detection limit of 0.15 mg L−1. Ultimately, the developed µPAD was applied for the determination of gold in ore samples. The obtained results were in good agreement with those obtained from standard method. The combination of fire assay and µPAD in the determination of gold in geological samples improved the detection limit based on enrichment factor of 75.

Droplet Formation and Emulsification using Microfluidic Channels: A Review

For the production of simple to complex emulsions, Microfluidic channels are becoming encouraging devices for the future. Microfluidic provides an investigation platform where the fluid quantity is in micro scale or nano scale. So performing experiments and investigation with the help of miniature devices offers numerous benefits such as very small quantity requirements of reagents, reduced wastage, and high control. There are several significant fluid dynamic applications at the micro-scale level, for instance, drug delivery (pharmaceuticals), flow chemistry, food processing, biotechnology, Industrial and environment sciences, life sciences and microbiology, etc. For the synthesis of emulsions through bulk emulsion procedure, the required accuracy in size and structure of fluid droplets usually get scarified. However, an emulsion can form accurately by fabricating even a single drop at a time with the help of micro fluidic devices. Also, the formation of highly mono disperse emulsion droplets is possible by using various microfluidic channel configurations. Further, the fabrication of higher-order or complex emulsions with the precise control over their structures can also be possible with this technology. The present article is presenting a review on the mechanism of generation of stable emulsion byusing microfluidic channels. The droplet generation mechanism is complex process where interfacial tension, viscous force, inertia effect and other geometrical parameters collectively govern the breakup process. For emulsion generation, various passive methods like Flow focusing, Co-flowing, membrane emulsification and T-shape junctions with their governing mechanism are discussed. Also the effect of physical parameters such as temperature, viscosity and interfacial tension are summarized in this article.

Biofouling-resistant tubular fluidic devices with magneto-responsive dynamic walls.

Biofouling of tubular fluidic devices limits the stability, accuracy, and long-term uses of lab-on-a-chip systems. Healthcare-associated infection by biofilm formations on body-indwelling and extracorporeal tubular medical devices is also a major cause of mortality and morbidity in patients. Although diverse antifouling techniques have been developed to prevent bacterial contamination of fluidic devices based on antimicrobial materials or nanoscale architectures, they still have limitations in biocompatibility, long-term activity, and durability. In this study, a new conceptual tubular fluidic device model that can effectively suppress bacterial contamination based on dynamic surface motions without using bactericidal materials or nanostructures is proposed. The fluidic device is composed of a magneto-responsive multilayered composite. The composite tube can generate dynamic surface deformation with controlled geometries along its inner wall in response to a remote magnetic field. The magnetic field-derived surface wave induces the generation of vortices near the inner wall surface of the tube, enabling sweeping of bacterial cells from the surface. As a result, the dynamic composite tube could effectively prevent biofilm formation for an extended time of 14 days without surface modification with chemical substances or nanostructures.

Simulation study of micro fluidic device for biosensor application

The word sensors have got huge importance in the modern world as they detect and analyse the data acquired from the physical world. Nowadays biosensors are used in hospitals as well as in houses for diagnosing medical conditions of a patient. The biosensors are used to detect biological or physicochemical information of a patient. The basic components of the biosensor include a transducer and a receptor. Here in this work, a biosensor model was designed and simulated using the software COMSOL Multiphysics. The flow parameters are identified using a convection micro fluidic device which was extended to the concept for biosensor simulation to know the characteristics of the body fluids. Micro fluids in biosensors will react with the biological components of a patient and the resulting signals are detected by the use transducer. The convection biosensor simulation was performed to find the concentration of adsorbed species in the fluids. The basic model of micro fluidic device with three inlets filled with water was simulated. Convection region of analyte molecule from one inlet and convection region of analyte molecule from two inlets were studied in detail. It was observed that, the flow velocity of the solvent decreases due to more concentration of the solute. The proposed model of biosensor can be used to find out the concentration of urine in blood or vice versa depending on the application like dialysis or blood testing. This can be further used to check the abnormal level of harmful impurities in the blood that affects the body. The study shows that, the convection sensor with one inlet flow is useful for the modelling biosensor. The data obtained from the simulation can be used for the hardware implementation in future.

Routing of Fluidic Circuits Using Skeletons of Polygonal Figures and Compound Splines

Routing of channels between elementary fluidic elements is an important stage in the design of new fluidic devices. This paper considers usage skeletons of polygonal figures and compound splines in routing of fluidic circuits.

Review on micromachining of pyrex glass using wire-ecdm

Pyrex glass has a huge range of applications such as micro optics, mechanical inertial sensors, micro-pumps, micro fluidic devices, biochip etc because of its excellent physical and chemical properties such as high chemical resistance, heat resistance, high electrical isolation, large optical transmission range, biocompatibility, low thermal and electrical conductivity, good chemical stability. Due to the hardness and brittleness properties, Pyrex glass has poor mach inability. It is very complicated to machine Pyrex glass by using conventional processes. Travelling wire electrochemical spark machining (TW-ECSM) is an emerging technique for micromachining of non-conductive materials. In TWECSM, the material of the work piece is melted, vaporized and eroded due to the transmission of spark energy to the work piece. Surface roughness is a very important aspect if we are doing micro aching of a material. The literature reveals the work done by various researchers for the micromachining of Pyrex glass. However very less work has been done on Pyrex glass. So in this paper, work done by various researchers on Pyrex glass, Use of TW-ECDM for micro aching is reviewed, scopes for further research have been identified.

Sex selection techniques and their implications

Abstract Sex selection techniques provide economic benefits to dairy and beef herd management. Therefore, the development of such techniques has attracted the attention of reproductive biologists. There have been numerous studies concerning the development of sex selection techniques. As the sex of the offspring is determined by certain chromosomes, namely the X and Y chromosomes in mammals, most studies have focused on sperm sexing, attempting to separate the X and Y chromosome-bearing sperm based on differences in deoxyribonucleic acid (DNA) content, head size/volume, motility, and immunological specificity. However, most of these methods have failed to show reproducibility. Only the flow cytometric method has been confirmed to be accurate and reliable thus far. More than three decades have passed since this technique was first developed. The sexed semen produced with the method is currently commercialized and widely used for artificial insemination (AI) in cattle around the world. Recently, however, another technique based on differences in DNA contents using a fluidics device was developed by a commercial company. Studies focused on immunological approaches and the modification of sperm motility have also described the successful separation of the two types of sperm. Therefore, the present review evaluated the available sex selection techniques and their implications.

Coupling fluid flow to hydrogel fluidic devices with reversible "pop-it" connections.

Hydrogels are soft, water-based polymer gels that are increasingly used to fabricate free-standing fluidic devices for tissue and biological engineering applications. For many of these applications, pressurized liquid must be driven through the hydrogel device. To couple pressurized liquid to a hydrogel device, a common approach is to insert tubing into a hole in the gel; however, this usually results in leakage and expulsion of the tubing, and other options for coupling pressurized liquid to hydrogels remain limited. Here, we describe a simple coupling approach where microfluidic tubing is inserted into a plastic, 3D-printed bulb-shaped connector, which "pops" into a 3D-printed socket in the gel. By systematically varying the dimensions of the connector relative to those of the socket entrance, we find an optimal head-socket ratio that provides maximum resistance to leakage and expulsion. The resulting connection can withstand liquid pressures on the order of several kilopascals, three orders of magnitude greater than traditional, connector-free approaches. We also show that two-sided connectors can be used to link multiple hydrogels to one another to build complex, reconfigurable hydrogel systems from modular components. We demonstrate the potential usefulness of these connectors by established long-term nutrient flow through a 3D-printed hydrogel device containing bacteria. The simple coupling approach outlined here will enable a variety of applications in hydrogel fluidics.

Integration of sequential analytical processes into sub-100 nm channels: volumetric sampling, chromatographic separation, and label-free molecule detection.

The progress of nanotechnology has developed nanofluidic devices utilizing nanochannels with a width and/or depth of sub-100 nm (101 nm channels), and several experiments have been implemented in ultra-small spaces comparable to DNAs and proteins. However, current experiments utilizing 101 nm channels focus on a single function or operation; integration of multiple analytical operations into 101 nm channels using nanofluidic circuits and fluidic control has yet to be realized despite the advantage of nanochannels. Herein, we report the establishment of a label-free molecule detection method for 101 nm channels and demonstration of sequential analytical processes using integrated nanofluidic devices. Our absorption-based detection method called photothermal optical diffraction (POD) enables non-invasive label-free molecule detection in 101 nm channels for the first time, and the limit of detection (LOD) of 1.8 μM is achieved in 70 nm wide and deep nanochannels, which corresponds to 7.5 molecules in the detection volume of 7 aL. As a demonstration of sampling in 101 nm channels, aL-fL volumetric sampling is performed using 90 nm deep cross-shaped nanochannels and pressure-driven fluidic control from three directions. Finally, the POD and volumetric sampling are combined with nanochannel chromatography, and separation analysis in 101 nm channels is demonstrated. The experimental results reported in this paper will contribute to the advances in 101 nm fluidic devices which have the potential to provide a novel platform for chemical/biological analyses.

Plasmonic nanobowtiefluidic device for sensitive detection of glioma extracellular vesicles by Raman spectrometry.

Cancer cells shed into biofluids extracellular vesicles (EVs) - nanoscale membrane particles carrying diagnostic information. EVs shed by heterogeneous populations of tumor cells offer a unique opportunity to access biologically important aspects of disease complexity. Glioblastoma (GBM) exemplifies cancers that are incurable, because their temporal dynamics and molecular complexity evade standard diagnostic methods and confound therapeutic efforts. Liquid biopsy based on EVs offers unprecedented real-time access to complex tumour signatures, but it is not used clinically due to inefficient testing methods. We report on a nanostructured microfluidic-device that employs SERS for unambiguous identification of EVs from different GBM cell populations. The device features fabless plasmonic nanobowties for label-free and non-immunological SERS detection of EVs. This nanobowtiefluidic device combines the advanced characteristics of plasmonic nanobowties with a high throughput sample-delivery system for concentration of the analytes in the vicinity of the detection site. We showed theoretically and experimentally that the fluidic device assists the monolayer distribution of the EVs, which dramatically increase the probability of EV's existence in the laser illumination area. In addition, the optimized fabless nanobowtie structures with an average electric field enhancement factor of 9 × 105 achieve distinguishable and high intensity SERS signals. Using the nanobowtiefluidic and micro-Raman equipment, we were able to distinguish a library of peaks expressed in GBM EV subpopulations from two distinct glioblastoma cell lines (U373, U87) and compare them to those of non-cancerous glial EVs (NHA) and artificial homogenous vesicles (e.g. DOPC/Chol). This cost-effective and easy-to-fabricate SERS platform and a portable sample-delivery system for discerning the sub-population of GBM EVs and non-cancerous glial EVs may have broader applications to different types of cancer cells and their molecular/oncogenic signature.

High shear in situ exfoliation of 2D gallium oxide sheets from centrifugally derived thin films of liquid gallium.

A diversity of two-dimensional nanomaterials has recently emerged with recent attention turning to the post-transition metal elements, in particular material derived from liquid metals and eutectic melts below 330 °C where processing is more flexible and in the temperature regime suitable for industry. This has been explored for liquid gallium using an angled vortex fluidic device (VFD) to fabricate ultrathin gallium oxide (Ga2O3) sheets under continuous flow conditions. We have established the nanosheets to form highly insulating material and have electrocatalytic activity for hydrogen evolution, with a Tafel slope of 39 mV dec−1 revealing promoting effects of the surface oxidation (passivation layer).

Sub-micron moulding topological mass transport regimes in angled vortex fluidic flow.

Shear stress in dynamic thin films, as in vortex fluidics, can be harnessed for generating non-equilibrium conditions, but the nature of the fluid flow is not understood. A rapidly rotating inclined tube in the vortex fluidic device (VFD) imparts shear stress (mechanical energy) into a thin film of liquid, depending on the physical characteristics of the liquid and rotational speed, ω, tilt angle, θ, and diameter of the tube. Through understanding that the fluid exhibits resonance behaviours from the confining boundaries of the glass surface and the meniscus that determines the liquid film thickness, we have established specific topological mass transport regimes. These topologies have been established through materials processing, as spinning top flow normal to the surface of the tube, double-helical flow across the thin film, and spicular flow, a transitional region where both effects contribute. The manifestation of mass transport patterns within the film have been observed by monitoring the mixing time, temperature profile, and film thickness against increasing rotational speed, ω. In addition, these flow patterns have unique signatures that enable the morphology of nanomaterials processed in the VFD to be predicted, for example in reversible scrolling and crumbling graphene oxide sheets. Shear-stress induced recrystallisation, crystallisation and polymerisation, at different rotational speeds, provide moulds of high-shear topologies, as ‘positive’ and ‘negative’ spicular flow behaviour. ‘Molecular drilling’ of holes in a thin film of polysulfone demonstrate spatial arrangement of double-helices. The grand sum of the different behavioural regimes is a general fluid flow model that accounts for all processing in the VFD at an optimal tilt angle of 45°, and provides a new concept in the fabrication of novel nanomaterials and controlling the organisation of matter.

Vortex fluidics mediated non-covalent physical entanglement of tannic acid and gelatin for entrapment of nutrients.

We have developed a simple process for the entrapment of nutrients in shear stress induced non-covalent physically entangled tannic acid-gelatin gel in a thin film vortex fluidic device (VFD) operating under continuous flow. This allows control of the porosity and surface area of the pores in order to improve the nutrient entrapment capacity. The VFD microfluidic platform simplifies the processing procedure of physically entangled biopolymers, as a time and cost saving one-step process devoid of any organic solvents, in contrast to the conventional homogenization process, which is also inherently complex, involving multiple-step processing. Moreover, the use of homogenization (as a benchmark to entrap nutrients) afforded much larger porosity and surface area of pores, with lower entrapment capacity of nutrients. Overall, the VFD processing provides a new alternative, bottom-up approach for easy, scalable processing for materials with a high nutrient entrapment capacity.

Fully 3D printed fluidic devices with integrated valves and pumps for flow injection analysis.

The use of a PolyJet 3D printer to create a microfluidic device that has integrated valves and pumps is described. The process uses liquid support and stacked printing to result in fully printed devices that are ready to use within minutes of fabrication after minimal post-processing. A unique feature of PolyJet printing is the ability to incorporate several different materials of varying properties into one print. In this work, two commercially available materials were used: a rigid-transparent plastic material (VeroClear) was used to define the channel regions and the bulk of the device, while the pumps/valves were printed in a flexible, rubber-like material (Agilus30). The entire process, from initial design to testing takes less than 4 hours to complete. The performance of the valves and pumps were characterized by fluorescence microscopy. A flow injection analysis device that enabled the discrete injections of analyte plugs was created, with on-chip pumps being used to move the fluid streams. The injection process was found to be reproducible and linearly correlated with changes in analyte concentration. The utility was demonstrated with the injection and rapid lysis of fluorescently-labeled endothelial cells. The ability to produce a device with integrated pumps/valves in one process significantly adds to the applicability of 3D printing to create microfluidic devices for analytical measurements.

High shear spheroidal topological fluid flow induced coating of polystyrene beads with C60 spicules.

Spheroidal spicular like topological fluid flow in an angled vortex fluidic device (VFD) housing a 20 mm diameter tube with a hemispherical base rotating at 4k rpm and tilted at 45° is effective in reducing the thermodynamic equilibrium concentration of fullerene C60 in toluene, with the formation of spicules of the material under continuous flow processing. Under the same operational conditions in the presence of polystyrene beads 2 to 6 μm in diameter, spicules of C60ca. 150 nm in length grow on their surfaces. This establishes that the spheroidal topological fluid flow in the VFD prevails while enveloping spheroidal like particles of such size.

High shear vortex fluidic morphologically controlled polysulfone formed under anhydrous conditions

Polysulfone (PSF) was prepared under anhydrous conditions in DMSO, under high shear in a vortex fluidic device (VFD) operating under confined mode thereby avoiding the use of chlorinated solvents, unlike in conventional batch processing.

Azide-alkyne cycloadditions in a vortex fluidic device: enhanced "on water" effects and catalysis in flow.

The Vortex Fluidic Device is a flow reactor that processes reactions in thin films. Running the metal-free azide-alkyne cycloaddition in this reactor revealed a dramatic enhancement of the "on water" effect. For the copper-catalyzed azide-alkyne cycloaddition, stainless steel or copper jet feeds were effective reservoirs of active copper catalyst.

Design Guidelines for Thermal Comfort and Energy Consumption of Triple Glazed Fluidic Windows on Building Level

AbstractThere has been a growing trend for buildings with large glazing size. As a trade‐off, this comes with enhanced solar heat input and/or reduced thermal insulation. Several approaches are being followed to reduce the energy consumption in these buildings, including the prolific field of smart windows. In a previous report, a fluidic window device for thermal harvesting and air‐conditioning was introduced. Using this example, the impact of a building's window‐to‐wall ratio on the triple glazed fluidic window's energy consumption and user thermal comfort is evaluated, providing design guidelines for large‐scale implementation of such smart windows with real‐world buildings. The analysis shows that the proposed window design reduces the primary energy demand as compared to using a conventional air‐conditioning system. Building simulation results indicate that the system enables satisfying thermal comfort for buildings with different window‐to‐wall ratios. Although a higher window‐to‐wall ratio improves the heat pump efficiency, it requires more heating and cooling energy. On‐device photovoltaic modules may be used for changing this relationship. In this case, the proposed device may become self‐sufficient once the transfer efficiency is high enough. It is argued that similar considerations should be applied to other types of smart window technologies.

Sonoporation enables high-throughput loading of trehalose into red blood cells

Despite recent advances in biostabilization, clinical blood supplies still experience shortages and storage limitations for red blood cells (RBCs) have not yet been sufficiently addressed. Storing RBCs in a frozen or dried state is an appealing solution to address storage limitations, but many promising cryoprotectants, including the non-reducing sugar trehalose, are impermeant to mammalian cell membranes and cannot be utilized effectively using currently available compound-loading methods. We found that transient pore formation induced by ultrasound and microbubbles (sonoporation) offers an effective means of loading trehalose into RBCs to facilitate long-term storage in a frozen or desiccated state. The protective potential of trehalose loading was demonstrated by freezing processed RBCs at −1 °C/min to −80 °C, then either storing the cells at −80 °C or lyophilizing them. RBCs were either thawed or rehydrated after 42 days of storage and evaluated for membrane integrity and esterase activity to estimate recovery and cell viability. The intracellular concentration of trehalose reached 40 mM after sonoporation and over 95% of treated RBCs were recovered after loading. Loading of trehalose was sufficient to maintain RBC morphology and esterase activity in most cells during freezing (>90% RBC recovery) and to a lower degree after lyophilization and rehydration (>20% recovery). Combining sonoporation with an integrated fluidics device allowed for rapid loading of up to 70 mM trehalose into RBCs. These results demonstrate the potential of sonoporation-mediated trehalose loading to increase recovery of viable RBCs, which could lead to effective methods for long-term stabilization of RBCs.

Fluidic and Mechanical Thermal Control Devices

AbstractIn recent years, intensive studies on thermal control devices have been conducted for the thermal management of electronics and computers as well as for applications in energy conversion, chemistry, sensors, buildings, and outer space. Conventional cooling or heating techniques realized using traditional thermal resistors and capacitors cannot meet the thermal requirements of advanced systems. Therefore, new thermal control devices are being investigated to satisfy these requirements. These devices include thermal diodes, thermal switches, thermal regulators, and thermal transistors, all of which manage heat in a manner analogous to how electronic devices and circuits control electricity. To design or apply these novel devices as well as thermal control principles, this paper presents a systematic and comprehensive review of the state‐of‐the‐art of fluidic and mechanical thermal control devices that have already been implemented in various applications for different size scales and temperature ranges. Operation principles, working parameters, and limitations are discussed and the most important features for a particular device are identified.