Small Volumes Of Fluid Research Articles

Thermo-Fluid Characteristics of High Temperature Molten Salt Flowing in Single-Leaf Type Hollow Paddles.

A single-leaf type paddle heat exchanger with molten salt as the working fluid is a proper option in high temperature heating processes of materials. In this paper, based on computational fluid dynamics (CFD) simulations, we present the thermo-fluid characteristics of high temperature molten salt flowing in single-leaf type hollow paddles in the view of both the first law and the second law of thermodynamics. The results show that the heat transfer rate of the hollow paddles is significantly greater than that of solid paddles. The penalty of the heat transfer enhancement is additional pressure drop and larger total irreversibility (i.e., total entropy generation rate). Increasing the volume of the fluid space helps to enhance the heat transfer, but there exists an upper limit. Hollow paddles are more favorable in heat transfer enhancement for designs with a larger height of the paddles, flow rate of molten salt and material-side heat transfer coefficient. The diameter of the flow holes influences the pressure drop strongly, but their position is not important for heat transfer in the studied range. Other measures of modifying the fluid flow and heat transfer like internal baffles, more flow holes or multiple channels for small fluid volume are further discussed. For few baffles, their effects are limited. More flow holes reduce the pressure drop obviously. For the hollow paddles with small fluid volume, it is possible to increase the heat transfer rate with more fluid channels. The trade-off among fluid flow, heat transfer and mechanical strength is necessary. The thermo-fluid characteristics revealed in this paper will provide guidance for practical designs.

Micropipette-powered droplet based microfluidics.

Droplet-based microfluidics, using water-in-oil emulsion droplets as micro-reactors, is becoming a widespread method for performing assays and especially in the cell biology field. Making a simple and highly portable system for creating emulsion droplets would help to continue the popularization of such a technique. Also, the ability to emulsify all the samples would strengthen this compartimenlization technique to handle samples with limited volume. Here, we propose a strategy of droplet formation that combines a classical flow-focusing microfluidic chip, which could be commercially available, with a standard laboratory adjustable micropipette. The micropipette is used as a negative pressure generator for controlling liquid flows. In that way, emulsification does neither require any electrical power supply nor a cumbersome device and functions with small liquid volumes. Droplet formation can be easily and safely performed in places with limited space, opening a wide range of applications especially in biological laboratory environments with higher level of safety regulations, i.e., BSL-3/4. Fortunately, the present methodology that involves small fluid volumes, and thus possible time dependent flow conditions, allows to minimize dead volume while keeping drops' size homogeneous. A physical characterization of droplet production and a model that describes the emulsion features, in terms of drop size and size distribution, are proposed for rationalizing the performances of the micropipette-powered emulsification process.

A Novel, Nonenzymatic Strategy for Stable, Optical Glucose Detection in Small Volumes of Fluid

The performance of any continuous glucose monitor (CGM) cannot exceed the performance of the underlying glucose sensor. Commercially available CGMs are built around the enzyme glucose oxidase. However, the performance of the enzyme is known to drift over time; accordingly, existing CGMs must be calibrated over periods of hours to days and replaced over periods of weeks. To overcome these fundamental limitations, we have developed a non-enzymatic glucose detection strategy that offers the promise of significantly improved stability and sensitivity. Specifically, we have designed and synthesized a water-soluble, molecular recognition element, which binds glucose with appropriate specificity and selectivity (Kd = 1.9 mM for glucose vs. Kd = 3.3 mM for fructose). The molecular recognition of glucose by our synthetic probes activates interactions between fluorescence-based reporters. Moreover, by coupling the recognition element with a light-harvesting molecular system with high optical cross-section, we are able to amplify optical signals that betray the presence of glucose, making it possible to carry out measurements in volumes as small as picoliters using off-the-shelf LEDs and photodetectors. Our detection platform also offers broad tunability: by altering the molecular recognition element and/or optical reporter we seek to achieve stable, optical detection of other sugars and biomarkers. Disclosure B. Wang: Research Support; Self; American Diabetes Association. G. Bazan: None. S. Pennathur: Stock/Shareholder; Self; Laxmi Therapeutic Devices. Research Support; Self; American Diabetes Association, JDRF. B. Queenan: Research Support; Self; American Diabetes Association. K. Scida: Research Support; Self; American Diabetes Association.

Synthesis of Biomaterials Utilizing Microfluidic Technology.

Recently, microfluidic technologies have attracted an enormous amount of interest as potential new tools for a large range of applications including materials synthesis, chemical and biological detection, drug delivery and screening, point-of-care diagnostics, and in-the-field analysis. Their ability to handle extremely small volumes of fluids is accompanied by additional benefits, most notably, rapid and efficient mass and heat transfer. In addition, reactions performed within microfluidic systems are highly controlled, meaning that many advanced materials, with uniform and bespoke properties, can be synthesized in a direct and rapid manner. In this review, we discuss the utility of microfluidic systems in the synthesis of materials for a variety of biological applications. Such materials include microparticles or microcapsules for drug delivery, nanoscale materials for medicine or cellular assays, and micro- or nanofibers for tissue engineering.

Analytical Scheme Leading to Integrated High-Sensitivity Profiling of Glycosphingolipids Together with N- and O-Glycans from One Sample.

Glycoconjugates are directly or indirectly involved in many biological processes. Due to their complex structures, the structural elucidation of glycans and the exploration of their role in biological systems have been challenging. Glycan pools generated through release from glycoprotein or glycolipid mixtures can often be very complex. For the sake of procedural simplicity, many glycan profiling studies choose to concentrate on a single class of glycoconjugates. In this paper, we demonstrate it feasible to cover glycosphingolipids, N-glycans, and O-glycans isolated from the same sample. Small volumes of human blood serum and ascites fluid as well as small mouse brain tissue samples are sufficient to profile sequentially glycans from all three classes of glycoconjugates and even positively identify some mixture components through MALDI-MS and LC-ESI-MS. The results show that comprehensive glycan profiles can be obtained from the equivalent of 500-μg protein starting material or possibly less. These methodological improvements can help accelerating future glycomic comprehensive studies, especially for precious clinical samples. Graphical Abstract Outline of glycan profiling procedures.

Nanoparticle Enhancement Cascade for Sensitive Multiplex Measurements of Biomarkers in Complex Fluids with Surface Plasmon Resonance Imaging.

There is a large unmet need for reliable biomarker measurement systems for clinical application. Such systems should meet challenging requirements for large scale use, including a large dynamic detection range, multiplexing capacity, and both high specificity and sensitivity. More importantly, these requirements need to apply to complex biological samples, which require extensive quality control. In this paper, we present the development of an enhancement detection cascade for surface plasmon resonance imaging (SPRi). The cascade applies an antibody sandwich assay, followed by neutravidin and a gold nanoparticle enhancement for quantitative biomarker measurements in small volumes of complex fluids. We present a feasibility study both in simple buffers and in spiked equine synovial fluid with four cytokines, IL-1β, IL-6, IFN-γ, and TNF-α. Our enhancement cascade leads to an antibody dependent improvement in sensitivity up to 40 000 times, resulting in a limit of detection as low as 50 fg/mL and a dynamic detection range of more than 7 logs. Additionally, measurements at these low concentrations are highly reliable with intra- and interassay CVs between 2% and 20%. We subsequently showed this assay is suitable for multiplex measurements with good specificity and limited cross-reactivity. Moreover, we demonstrated robust detection of IL-6 and IL-1β in spiked undiluted equine synovial fluid with small variation compared to buffer controls. In addition, the availability of real time measurements provides extensive quality control opportunities, essential for clinical applications. Therefore, we consider this method is suitable for broad application in SPRi for multiplex biomarker detection in both research and clinical settings.

Suppression of Urinary Voiding by Conditional High Frequency Stimulation of the Pelvic Nerve in Conscious Rats.

Female Wistar rats were instrumented to record bladder pressure and to stimulate the left pelvic nerve. Repeated voids were induced by continuous infusion of saline into the bladder (11.2 ml/h) via a T-piece in the line to the bladder catheter. In each animal tested (n = 6) high frequency pelvic nerve stimulation (1–3 kHz, 1–2 mA sinusoidal waveform for 60 s) applied within 2 s of the onset of a sharp rise in bladder pressure signaling an imminent void was able to inhibit micturition. Voiding was modulated in three ways: (1) Suppression of voiding (four rats, n = 13 trials). No fluid output or a very small volume of fluid expelled (<15% of the volume expected based on the mean of the previous 2 or 3 voids). Voiding suppressed for the entirety of the stimulation period (60 s) and resumed within 37 s of stopping stimulation. (2) Void deferred (four rats, n = 6 trials). The imminent void was suppressed (no fluid expelled) but a void occurred later in the stimulation period (12–44 s, mean 24.5 ± 5.2 s after the onset of the stimulation). (3) Reduction in voided volume (five rats, n = 20 trials). Voiding took place but the volume of fluid voided was 15–80% (range 21.8–77.8%, mean 45.3 ± 3.6%) of the volume expected from the mean of the preceding two or three voids. Spontaneous voiding resumed within 5 min of stopping stimulation. Stimulation during the filling phase in between voids had no effect. The experiments demonstrate that conditional high frequency stimulation of the pelvic nerve started at the onset of an imminent void can inhibit voiding. The effect was rapidly reversible and was not accompanied by any adverse behavioral side effects.

The Effects of Fluid Resuscitation on Renal and Cardiac Mitochondrial Function in a Severely Burned Swine Model

Severe burn injury covering over 30% of the total body surface area (TBSA) results in a systemic inflammatory response which can lead to multi organ dysfunction (MOD). Intravenous (IV) fluid resuscitation is a key component in the acute phase of burn treatment, however the volumes and types of fluids used (e.g., crystalloids vs. colloids) remain controversial. While previous studies have shown mitochondrial damage in organs such as heart and kidneys post‐burn, the effects of IV fluids on mitochondrial function have not been studied. The purpose of this study is to determine the effects of small volumes of crystalloid or colloid fluids on mitochondrial function following severe burns in a swine model. Anesthetized Yorkshire swine (n=14) sustained 40% TBSA full‐thickness contact burns with brass probes heated to 100°C placed in contact with the skin for 30 seconds. Animals were allowed to recover in metabolic cages and were given IV fluids (15 mL/kg/day) as either crystalloids (n=7) or colloids (n=7). Five non‐burned swine served as control. After 48 h, heart and kidney tissue were harvested and mitochondrial function was analyzed by high resolution respirometry. Substrates were added to determine the maximum oxidative phosphorylation (OXPHOS). Then the ATP synthase inhibitor, oligomycin was added to determine Leak respiration. Mitochondrial efficiency was defined as the coupling control ratio (OXPHOS/Leak). Citrate synthase (CS) assay was used for normalization of the data, and statistical significance was set at p&lt;0.05. Mitochondrial abundance was significantly lower in swine kidney given colloid vs crystalloid (13.87 ± 2.35 vs 22.03 ± 1.68 nmol CS/ml/s, p&lt;0.05, respectively) and control (23.77 ± 3.55 nmol CS/ml/s, p&lt;0.05). Leak respiration per mitochondrion in heart tissues was significantly higher in burned swine given colloids than crystalloids (672.3 ± 82.74 vs 334.4 ± 50.27 pmol O2/mg/s/CS, p&lt;0.01) and non‐burned controls (254.1 ± 57.77 pmol O2/mg/s/CS, p&lt;0.01), indicating higher O2 respiration without ATP synthesis. We found heart mitochondria in swine given colloids were significantly less efficient than controls (54% ± 6 vs 76% ± 5, p&lt;0.05, respectively), which was not true after IV crystalloids (67% ± 7). This was also found in renal mitochondria where colloid (but not crystalloid‐treated) swine showed less ATP producing efficiency in the kidney than non‐burned controls (55% ± 6 vs 73% ± 5, p&lt;0.05, respectively). For the first time, our study examined the effects of different IV fluids on mitochondrial function following severe burns. Our data suggest that resuscitation with crystalloids may be protective of mitochondrial abundance and function within the first 48 h following severe burns. Future studies to address timing and volume of resuscitation fluid administration are needed.Support or Funding InformationThis study was supported by Military Burn Research Program Award# W81XWH‐16‐2‐0041.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Modelling and experimental verification of pressure relief synchronous control for small trapped fluid volumes

This paper presents a pressure relief synchronous control method for four small entrapped high-pressure fluid volumes on a huge hydraulic machine. Firstly, as the existing pressure relief methods cannot behave well for small entrapped high-pressure fluid volumes, a novel electrohydraulic proportional pressure relief circuit is proposed. The electrohydraulic proportional pressure relief circuit is composed of a proportional pressure relief valve, a damping orifice and a constant pressure source, through which the pressure can be relieved proportionally to the command signal. Secondly, as the machine is a manned hydropower carrier, a very safety-critical application, a simple and easy to implement hybrid control scheme consisting of a synchronization controller and a pressure tracking controller is developed. As the pressure relief circuit has a wide range of operating conditions and parameter uncertainties, a practical self-tuning fuzzy proportion integration (PI) pressure tracking controller with feedforward is proposed, and a master–slave PI synchronization pressure controller with dead band is employed for the four entrapped fluid volumes. Finally, the experimental verification is implemented on a test stand to demonstrate the effectiveness of the proposed synchronous control system. The experimental results confirm that the pressure deviations among the four small entrapped high-pressure fluid volumes are bound within [Formula: see text].

Design of Application-Specific Architectures for Networked Labs-on-Chips

Labs-on-Chips (LoCs) implement laboratory procedures on a single chip and are successfully used for chemical and biomedical applications. A promising and emerging realization of such chips are Networked LoCs (NLoCs) in which small volumes of fluids, so-called droplets, flow in closed channels of submillimeter diameters. NLoCs allow for an incubation and storage of assays over a long period of time and, hence, avoid evaporation and unwanted reactions. To increase the flexibility, effectiveness, and reusability, network functionalities allow to passively route droplets in channels and, hence, to dynamically select operations depending on the executed experiment. However, only manually designed architectures are considered for NLoCs thus far. They frequently suffer from large execution times and/or a high contamination of channels. To overcome these drawbacks, we propose the consideration of application-specific architectures for NLoCs. To this end, an automatic design method is proposed which, for a given set of experiments as well as constraints and objectives from the designer, is able to generate an optimized NLoC architecture realizing these experiments. Evaluations and case studies demonstrate the potential of the proposed solution for design exploration. Moreover, we are able to show that application-specific architectures are capable of realizing experiments in just a fraction of the time needed by architectures used thus far as well as with a substantially reduced contamination.

Design and Development of Micro-channel using PDMS for Biomedical Applications

Micro channels provide the vital breakthrough in many of the applications like drug delivery system. In recent years many of the drugs consumed orally or through injections are at higher doses compared to the actual need for treating which may intern causes after effect of the medicine though initially the disease may apparently decreased. Hence, there is a much need for the systems where we can able to provide results with small sample or fluid volumes. In this work the micro channel of width 100 microns are developed in clean room environment using photolithography on PDMS(Polydimethylsiloxane) material. PDMS material is a polymer which is inexpensive and biocompatible. PDMS is permeable to gas and impermeable to liquids. This allows to study the living cells and to generate flow of fluid through the channels The PDMS material has been studied with the solid of PDMS developed in which the micro channels are designed and fabricated in clean room environment. The channel consists of inlet, outlet and eight trapping chambers, which can be used for bio particle separator and micro incubator. These channels are tested and verified for the flow through the channels and droplets were generated through the trapping channel. The channels show excellent strength and optimum flow through the channel width of 100 micron and depth of 40 micron

A Pumpless Acoustofluidic Platform for Size-Selective Concentration and Separation of Microparticles.

We have designed a pumpless acoustofluidic device for the concentration and separation of different sized particles inside a single-layered straight polydimethylsiloxane (PDMS) microfluidic channel. The proposed device comprises two parallel interdigitated transducers (IDTs) positioned underneath the PDMS microchannel. The IDTs produce high-frequency surface acoustic waves that generate semipermeable virtual acoustic radiation force field walls that selectively trap and concentrate larger particles at different locations inside the microchannel and allow the smaller particles to pass through the acoustic filter. The performance of the acoustofluidic device was first characterized by injecting into the microchannel a uniform flow of suspended 9.9 μm diameter particles with various initial concentrations (as low as 10 particles/mL) using a syringe pump. The particles were trapped with ∼100% efficiency by a single IDT actuated at 73 MHz. The acoustofluidic platform was used to demonstrate the pumpless separation of 12.0, 4.8, and 2.1 μm microparticles by trapping the 12 and 4.8 μm particles using the two IDTs actuated at 73 and 140 MHz, respectively. However, most of the 2.1 μm particles flowed over the IDTs unaffected. The acoustofluidic device was capable of rapidly processing a large volume of sample fluid pumped through the microchannel using an external syringe pump. A small volume of the sample fluid was processed through the device using a capillary flow and a hydrodynamic pressure difference that did not require an external pumping device.

The Magmatic to Magmatic-Hydrothermal Evolution of the El Laco Deposit (Chile) and Its Implications for the Genesis of Magnetite-Apatite Deposits

Abstract The geology and geochemistry of the El Laco iron oxide deposit (Central Andes, Chile) support a genesis related to the ascent, degassing, and subvolcanic emplacement of an unusual oxidized silica-poor but water-and iron-rich melt that took place during the growth of the host Pliocene-Holocene andesitic volcano. The model proposed in this paper for the evolution of the deposit involves the formation of a shallow telescoped magmatichydrothermal system with complex melt-fluid unmixing in a vertical column of less than 1 km. The dominant mineralization occurs as large stratabound apatite-poor magnetite bodies interfingered with an andesite host and rooted in vertical dikes of magnetite with minor apatite. The stratabound mineralization is crosscut by abundant coeval diatreme-like structures indicative of vigorous degassing. The andesite underlying the mineralization is pervasively replaced by a high-temperature alkali-calcic alteration assemblage (K feldspar-diopside-magnetite-scapolite) that includes coarse-grained diopside-magnetite-anhydrite veins and large subvertical bodies of magmatic-hydrothermal breccias. The host andesite also shows a large strata-bound steam-heated acid alteration that is devoid of any magnetite but has produced the replacement of a significant proportion of the early magnetite by hematite. The El Laco system is rich in anhydrite but poor in sulfides, suggesting that there were persistent oxidizing conditions that inhibited the formation of a sulfide-bearing mineralization. Field evidence, oxygen isotope geothermometry, and thermodynamic constraints suggest that the magnetite mineralization formed close to the surface at temperatures above 800°C. The magnetite textures, similar to those of subaerial low-viscosity basalts, and the presence of melt inclusions in the host andesite recording the presence of immiscible Fe-Mg-Ca-(Si-Ti-P-S) and Si-K-Na-Al melts, suggest that the magnetite ore formed by direct crystallization from an iron-rich melt; its chemistry inhibited the formation of most other magmatic phases except minor apatite, anhydrite, and diopside. The crystallization of the iron-rich melt at shallow depths promoted the separation of large amounts of two immiscible aqueous fluids: a dominant low-density vapor phase and a small volume of hypersaline fluid. Diopside-magnetite-anhydrite veins are interpreted as the product of the crystallization of the residual melts, whereas the interaction of the brine with the host andesite formed the deep alkali-calcic hydrothermal assemblage. The condensation and mixing of the low-density magmatic vapor with meteoric water produced the steam-heated alteration. Isotope data from the host andesite (87Sr/86Sr: 0.7066–0.7074; εNd: −5.5 to −4.1; δ18Owhole rock: 7.2–9.6‰; δ18Omagnetite: 5.1–6.2‰) and an underlying andesite porphyry (87Sr/86Sr: 0.7075–0.7082; εNd: −5.9 to −4.6) reflect the interaction of a primitive mantle melt with Andean crustal rocks. The isotope geochemistry of the magnetite ore (87Sr/86Sr: 0.7083; εNd: −5.4 to −5.1; δ18O 3.5–5.5‰) and the alkali-calcic alteration and related diopside-magnetite-anhydrite veins (87Sr/86Sr: 0.7080–0.7083; εNd: −5.1 to −4.6; δ18Odiopside: 7.2–8.2%c; δ18Omagnetite 4.4–6.3‰) show that the mineralization has a more crustal signature than the host andesite and all the volcanic rocks of the Central Andes. Therefore, ore-forming fluids/melts were not equilibrated with the host volcanic rocks and are interpreted as related to a deep yet undiscovered batch of highly contaminated igneous rocks. Crustal contamination is interpreted as due to major interaction of a juvenile melt with the underlying Late Mesozoic-Tertiary Salta Group, located 1 to 6 km beneath the volcano and which has high 87Sr/86Sr values (0.7140–0.7141).

Successful outcome in perinatal intravaginal torsion of testis in neonate: Long-term outcome

Introduction Perinatal testicular torsion can be intravaginal or extravaginal. Extravaginal torsion can be managed in an elective manner. Intravaginal torsion needs an urgent operation to maximize the viability of the testis. The history is vital to distinguish between the two diagnoses. We report a case in which a perinatal intravaginal torted testicle was successfully salvaged due to a timely exploration. This was a retrospective review of a case and literature review of perinatal testicular torsion. Case description A term baby was transferred to a tertiary pediatric surgical unit in the for surgical management of exomphalos minor. The child was noted to have normal testes. On the seventh day of life, he was noted to have a firm swelling in his right scrotum with purple discoloration. He was promptly reviewed by the surgical team. A perinatal torsion of intravaginal type was suspected and he was booked for emergency exploration. The surgical findings were 1) significant edema of the right scrotal wall, 2) a thickened tunica vaginalis and small volume of hemolyzed fluid, and 3) a bluish and congested torted testicle in intravaginal plane. Testis was de-rotated and color returned within 5 minutes. A three-point testicular fixation was performed bilaterally. He was reviewed in clinic for the following 2 years and found to have equal growth of the testicles, both of which were appropriately positioned within the scrotum. Results and conclusions This case highlights the importance of being aware that perinatal torsion can be extravaginal or intravaginal. The patient history is important to distinguish between the two diagnoses as proven by the above case. A positive outcome can be achieved with judicious assessment and emergent management of perinatal intravaginal torsions. Take-home message Clinicians should maintain a high level of suspicion of intravaginal torsion in all cases of perinatal testicular torsion.

Study of Permanent Shear Thinning of VM Polymer Solutions

The ultrashear viscometer (USV) has been adapted and employed to investigate the permanent shear thinning of polystyrene solutions in a series of phthalate ester base fluids. The permanent shear stability index based on viscosities measured at 106 s−1, PSSI(106), has been found to be a convenient way to express the magnitude of permanent shear thinning. When comparing permanent shear thinning at various shear rates in the USV, it is very important to take account of the different times of shear that are present at different shear rates. The PSSI(106) value divided by the total time of shear is then a useful way of quantifying and comparing permanent shear thinning rates. Tests using polystyrene in different viscosity base fluids have shown that this rate of permanent shear thinning depends on shear stress and not shear rate and varies linearly with polymer concentration. The rate of permanent shear thinning also varies exponentially with shear stress, suggestive of a stress-promoted polymer breakdown process. By using a small volume of test fluid in the USV and solvent extraction after a test, it has proved possible to obtain molecular weight distributions of polymer after shear using gel permeation chromatography (GPC). This indicates that the polymer breakdown process is different at low and high polymer concentrations, with molecule fragmentation at low polymer concentration but mid-chain scission at high concentration. A key feature of the USV is that, unlike other methods currently used to measure permanent shear thinning behaviour of engine oils, it subjects the test fluid to well-defined, controllable high shear conditions. Coupled with the use of GPC, this makes it possible for the first time to relate quantitatively the permanent shear thinning of engine oils to shear conditions and to polymer degradation response.

New nucleic acid testing devices to diagnose infectious diseases in resource-limited settings.

Point-of-care diagnosis based on nucleic acid testing aims to incorporate all the analytical steps, from sample preparation to nucleic acid amplification and detection, in a single device. This device needs to provide a low-cost, robust, sensitive, specific, and easily readable analysis. Microfluidics has great potential for handling small volumes of fluids on a single platform. Microfluidic technology has recently been applied to paper, which is already used in low-cost lateral flow tests. Nucleic acid extraction from a biological specimen usually requires cell filtration and lysis on specific membranes, while affinity matrices, such as chitosan or polydiacetylene, are well suited to concentrating nucleic acids for subsequent amplification. Access to electricity is often difficult in resource-limited areas, so the amplification step needs to be equipment-free. Consequently, the reaction has to be isothermal to alleviate the need for a thermocycler. LAMP, NASBA, HDA, and RPA are examples of the technologies available. Nucleic acid detection techniques are currently based on fluorescence, colorimetry, or chemiluminescence. For point-of-care diagnostics, the results should be readable with the naked eye. Nowadays, interpretation and communication of results to health professionals could rely on a smartphone, used as a telemedicine device. The major challenge of creating an "all-in-one" diagnostic test involves the design of an optimal solution and a sequence for each analytical step, as well as combining the execution of all these steps on a single device. This review provides an overview of available materials and technologies which seem to be adapted to point-of-care nucleic acid-based diagnosis, in low-resource areas.

Novel Microwave Torso Scanner for Thoracic Fluid Accumulation Diagnosis and Monitoring

Thoracic fluid accumulation is one of the significant and early-stage manifestations of fatal diseases, such as lung-cancer, liver-failure and congestive heart-failure. Currently, computational-tomography (CT)-Scan is the most widely used tool for the detection of thoracic fluid. Yet, it is unable to detect small amounts of fluid, has ionizing radiation and lacks mobility. On the other hand, microwave imaging systems have emerged as an accurate and portable complementary diagnostic tool. However, there is a lack of a complete clinical platform that can fulfill the requirements of accurate and reliable imaging. Therefore, a microwave torso scanner that is designed to meet those requirements is presented. In this system, two elliptical-arrays of microwave antennas (sensors) transmit signals towards the torso and collect the back-scattered signals. The captured signals are then processed by a frequency-based imaging algorithm to form microwave images that display a possible accumulated fluid. The system successfully detects and localized small volumes (3 mL) of fluid injected at different places inside a torso-phantom. As preparations for future clinical trials, the system is tested on healthy subjects to define the threshold range of healthy scenario images.

Highly integrated polymeric microliquid flow controller for droplet microfluidics

Microfluidic applications demand accurate control and measurement of small fluid flows and volumes, and the majority of approaches found in the literature involve materials and fabrication methods not suitable for a monolithic integration of different microcomponents needed to make a complex Lab-on-a-Chip (LoC) system. The present work leads to a design and manufacturing approach for problem-free monolithic integration of components on thermoplastics, allowing the production of excellent quality devices either as stand-alone components or combined in a complex structures. In particular, a polymeric liquid flow controlling system (LFCS) at microscale is presented, which is composed of a pneumatic microvalve and an on-chip microflow sensor. It enables flow regulation between 30 and 230 μl/min with excellent reproducibility and accuracy (error lower than 5%). The device is made of a single Cyclic Olefin Polymer (COP) piece, where the channels and cavities are hot-embossed, sealed with a single COP membrane by solvent bonding and metalized, after sealing, to render a fully functional microfluidic control system that features on-chip flow sensing. In contrast with commercially available flow control systems, the device can be used for high-quality flow modulation in disposable LoC devices, since the microfluidic chip is low cost and replaceable from the external electronic and pneumatic actuators box. Functionality of the LFCS is tested by connecting it to a microfluidic droplet generator, rendering highly stable flow rates and allowing generation of monodisperse droplets over a wide range of flow rates. The results indicate the successful performance of the LFCS with significant improvements over existing LFCS devices, facing the possibility of using the system for biological applications such as generating distinct perfusion modes in cell culture, novel digital microfluidics. Moreover, the integration capabilities and the reproducible fabrication method enable straightforward transition from prototype to product in a way that is lean, cost-effective and with reduced risk.

A two-dimensional inviscid model of the gravity-current head by Lagrangian block simulation

A two-dimensional inviscid model of the gravity-current head produced by the release of a relatively small volume of dense fluid from behind a tall lock gate is constructed by Lagrangian block simulation. Three numerical experiments are conducted for the lock’s height-to-length aspect ratios H/Lo = 8, 4 and 2. The front speeds obtained by the simulations agree with the laboratory observation for a similar range of aspect ratios. The floor velocity in the wake behind these heads is found to be greater than their front speed. The high floor velocity is caused by the impingement of the coherent wake vortex on the floor. It is a condition that permits these gravity-current heads to maintain their structural integrity so that the fine sediments can travel with the head over long distances on the ocean floor. The structural coherence of the current head depends on the lock aspect ratio. The gravity-current head produced by the release from the lock with the highest aspect ratio of H/Lo = 8 is most coherent and relatively has the greatest floor velocity and the least trailing current behind the head.

ELISA‐type assays of trace biomarkers using microfluidic methods

Recently, great progress has been achieved for analytical technologies for biological substances. Traditionally, detection methods for analytes mainly rely on large instrumental analyses. These methods require costly equipment, skilled operators and long measurement time despite their generally low sensitivity. In contrast, immunoassays are becoming more and more popular for it is powerful, inexpensive, and convenient nature. Immunoassay has a range of applications, because it employs antibody, a protein produced by plasma cells in the acquired immune system to identify and neutralize diverse pathogens and other exogenous substances. However, the sensitivity of conventional immunoassays so far is limited by their reaction principles and detection methods. The microfluidics technology is the one that manipulates small volumes of fluid and flow, which has the potential to miniaturize many laboratory procedures. Immunoassays on microfluidic devices have been studied extensively and have gained significant attention owing to intrinsic advantages offered by the assay platforms. The techniques have allowed the miniaturization of conventional immunoassay and bring the advantages such as small volumes of samples and reagents as well as the decrease of contamination, which results in the decline of false-positive results. Ultimately, the combination of immunoassays with microfluidics affords a promising platform for multiple, sensitive, and automatic point-of-care diagnostics. Recent achievements on microfluidic devices and immunoassay detection systems including digital assay employing single molecule will be introduced in detail and the strategies for faster and more sensitive configurations in microfluidic immunosensors will be highlighted. WIREs Nanomed Nanobiotechnol 2017, 9:e1457. doi: 10.1002/wnan.1457 For further resources related to this article, please visit the WIREs website.