Fluid Characteristics Research Articles

Experimental investigation of the rheological behavior and micro-morphology of the wormlike micelle cross-linked with polyelectrolyte-grafted nano silica and the associative polymer

This paper has investigated the rheological behavior and micro-morphology of CTAC wormlike micelle (WLM) which cross-linked with polyelectrolyte-grafted nanosilica (PEN) and nonionic hydrophobically-associating polymer (HAP). Cryo-transmission electron microscopy (Cryo-TEM) is adopted to observe the micro-morphology of the associative structure. Results show that PEN cross-linked with CTAC wormlike micelle exhibits higher zero-shear viscosity than the non-modified nano silica, and this viscosity is continuously raised as the PEN concentration is increased. PEN-micelle complex has excellent anti-salt properties and its zero-shear viscosity is increasing in a KCl concentration range of 0–10%. The shear viscosity of wormlike micelle is enhanced by HAP and polymer molecules dominate the rheological characteristic of the mixed fluid. The shear viscosity of HAP-micelle fluid is further increased by PEN. However, the rheological characteristic of the micelle-HAP-PEN complex is identical to that of wormlike micelle. The elasticity of wormlike micelle is noticeably enhanced by cross-linking with PEN and HAP. They stimulate the formation of micelle to significantly increase the length and rigidity of wormlike micelle. Surfactant molecules spontaneously arrange on the surface of PEN and grow outwards, which associates with HAP to generate the tighter three-dimensional network structure.

Investigating the Effect of Palm Kernel Shell Powder on the Rheological and Filtration Properties of Water Based Mud

During drilling operations, the use of drilling fluid plays a critical role, and over time, there has been considerable interest in enhancing drilling fluid characteristics in order to improve performance, reduce costs, and prevent environmental pollution. Deviating from conventional additives, recent studies have explored the use of alternative materials, as drilling fluid additives. In line with this trend, this study focuses on the laboratory investigation of the rheological and filtration properties of water-based drilling fluid treated with Palm Kernel Shell Powder (PKSP) with high viscosity polyanionic cellulose (PAC HV), used as control. To assess the impact of PKSP in water-based mud, experiments were carried out using concentrations spanning from 0.5g to 2.5g, temperatures of 27°C, 40°C, 60°C, and 80°C, and aging of 24, 48, and 72 hours. From the results the plastic viscosity of mud samples treated with PKSP were temperature dependent and also with increasing aging. The addition of PKSP showed improved performance in terms of reducing the filtrate volume as well as the cake thickness with increasing concentration of the additives, and the concentration that gave the best results across all aging duration was 2.5g. The mud weight and pH of all samples remained relatively constant, with no significant changes observed. However, PAC HV showed better results in all the cases of fluid loss and mud cake thickness. It could be attributed to the soluble contents in the PAC HV which increased the viscosity significantly and thus, kept the solid particles in suspension.

Characteristics of the Cerebrospinal Fluid in Septic Patients with Critical Illness Polyneuropathy - A Retrospective Cohort Study.

Critical illness polyneuropathy (CIP) is a complex disease commonly occurring in septic patients which indicates a worse prognosis. Herein, we investigated the characteristics of cerebrospinal fluid (CSF) in septic patients with CIP. This retrospective study was conducted between Match 1, 2018, and July 1, 2022. Patients with sepsis who underwent a CSF examination and nerve electrophysiology were included. The levels of protein, glucose, lipopolysaccharide, white blood cell (WBC), interleukin (IL)-1, IL-6, IL-8, and tumor necrosis factor (TNF) α in CSF were measured. The fungi and bacteria in CSF were also assessed. Among the 175 septic patients, 116 (66.3%) patients were diagnosed with CIP. 28-day Mortality in CIP patients was higher than that in non-CIP patients (25.0% vs. 10.2%, P = 0.02) which was confirmed by survival analysis. The results of propensity score matching analysis (PSMA) indicated a significant difference in the level of protein, WBC, IL-1, IL-6, IL-8, and TNFα present in the CSF between CIP patients and non-CIP patients. The results of the receiver operating characteristic (ROC) analysis showed that IL-1, WBC, TNFα, and their combined indicator had a good diagnostic value with an AUC > 0.8. The increase in the levels of WBC, IL-1, and TNFα in CSF might be an indicator of CIP in septic patients.

Investigating peristaltic flow of Newtonian fluid in a permeable channel: Effects of nonlinear curvature and wall properties

This investigation delves into the peristaltic flow characteristics of a Newtonian fluid within a permeable channel, emphasizing the influence of nonlinear curvature and wall properties. The study employs wave trains of varying amplitudes and phases to induce an asymmetric configuration along the channel boundaries. The curvature effects are contingent upon the ratio of channel width to wavelength, and the accuracy of results is maintained up to the second order in δ. To facilitate the derivation of closed-form solutions at higher levels, a domain transformation is executed, converting a channel with a variable cross section into one with a uniform cross section. To impose constraints on parameters and achieve a singular flux in the presence of a specified pressure gradient, a distinctiveness criterion is formulated. This study investigates the interplay of inertia and curvature on pumping and trapping, examining both symmetric and asymmetric channels. The pressure difference escalates with wave number in both channel configurations. Moreover, in the absence of inertial forces and flux, the impact of curvature on the pressure difference demonstrates a direct proportionality. Conversely, an augmentation in the permeability of the porous channel correlates with a reduction in the pressure difference. An intriguing observation arises as phase differences increase: the visibility of the bolus diminishes, and the streamlines become more prominent. This establishes a favorable environment for fluid flow, enhancing our understanding of the intricate dynamics at play in peristaltic flow within permeable channels.

An update on the study of synovial fluid in the geriatric patient.

The characteristics of synovial fluid (SF) in geriatric patients differ from those in younger patients. In Mexico, epidemiologic data on the incidence of different rheumatic diseases in geriatric patients are scarce. To describe the physical characteristics of geriatric SF and the prevalence of crystals in knee and other joint aspirates from patients with previously diagnosed joint disease. A retrospective study was performed with a baseline of 517 SF samples between 2011 and 2023. White blood cell count was performed by Neubauer chamber and crystals were identified by polarized light microscopy. Descriptive statistical analysis was performed and prevalence was reported as a percentage. The mean age of the adults was 73.5±5.0 years, 54.4% were women and 45.6% were men. The mean SF volume was 6.3±9.5mL in older adults and 15.3±24.9mL in those younger than 65 years. The mean viscosity in older adults was 9.5±4.5mm and the mean leukocyte count was 7352±16,402leukocytes/mm3. Seventy percent of the older adults' SFs were referred to the laboratory for osteoarthritis (OA), with lower proportions for rheumatoid arthritis (RA) (14.6%) and gout (5.1%). Of the crystals observed in the geriatric population, 14.6% corresponded to monosodium urate crystals (CUM) and 18.9% to calcium pyrophosphate crystals (CPP). The characteristics of LS in older adults were smaller volume, increased viscosity, and non-inflammatory. The main diagnoses were OA, RA, and gout. The crystal content of the SF of the geriatric population corresponded mainly to CPP.

Multisensors based on electrolyte-gated organic field-effect transistors (EGOFETs) with aptamers as recognition elements: current state of research

The review gives a systematic account of published data devoted to multisensor technologies for manufacturing effective miniature devices capable of simultaneous accurate determination of several analytes and/or characteristics of biological fluids. The use of electrolyte-gated field-effect transistors as a biosensing platform is considered in detail. The devices based on these transistors demonstrate record-low limits of detection and are easy for mass production. The use of electrolyte-gated field-effect transistors in combination with aptamers capable of specifically binding to various analytes forms the grounds for innovations in early medical diagnosis (label-free biomarker detection). The most successful examples of multisensor devices using these transistors are presented, and the prospects of using aptamers as a recognition element in these devices are demonstrated.<br>Bibliography — 154 references.

Microscopic occurrence and distribution of oil and water in situ shale: Evidence from nuclear magnetic resonance

Characterizing the microscopic occurrence and distribution of in-situ pore water and oil is crucial for resource estimation and development method selection of shale oil. In this paper, a series of nuclear magnetic resonance (NMR) experiments were conducted on shales from the Gulong Sag, Songliao Basin, China, at AR, WR-AR, WOR-AR, Dry, SO, and WR states. In-situ pore water and oil were reconstructed after WOR-AR. An improved T1–T2 pattern for shale oil reservoirs comprising water and oil was proposed to classify and quantitatively detect pore fluids at different occurrence states. The total and free oil contents derived from NMR T1–T2 spectra at AR states were found to correlate well with those from multistage Rock-Eval. Moreover, the NMR-calculated total and free oil are generally larger than those measured from multistage Rock-Eval, whereas adsorbed oil is the opposite, which implies that adsorbed, bound, and movable oils in shale pores can be accurately and quantitatively detected via NMR, without absorbed hydrocarbons in kerogen. As per the NMR T2 and T1–T2 spectra at WOR-AR state, the microdistributions of in-situ pore water and oil were clearly demonstrated. Adsorbed, bound, and movable oils primarily occur in the micropores (<100 nm), mesopores (100–1000 nm), and macropores (>1000 nm), respectively, whereas capillary-bound water is primarily correlated with micropores. Thus, the microscopic occurrence and distribution of adsorbed oil are remarkably affected by pore water, followed by bound oil, and movable oil is hardly affected. This study would be helpful in further understanding the microscopic occurrence characteristics of pore fluids in-situ shale oil reservoirs.

Determining the pore structure and fluid characteristics of different ranks of coal using nuclear magnetic resonance

The microstructure of coal reservoirs and their fluid-endowment characteristics are important indicators for evaluating coalbed methane during mining. This study aimed to investigate the influence mechanism of the nanopore structure of different coal ranks on the fluid distribution characteristics. Low-field nuclear magnetic resonance (NMR), centrifugal force, and heat treatment tests were conducted. The results indicated that as the degree of coal metamorphism increases, micro-transition pores increase significantly, mesopores–macropores decrease, and the nonhomogeneity of the pores increases. The optimum centrifugal forces for low-, middle-, and high-rank coals were 1.68, 1.08, and 1.08 MPa, respectively. The corresponding mean T2C1 (first T2 cutoff) values were measured as 8.01, 1.61, and 5.09 ms, respectively, while the mean T2C2 (second T2 cutoff) values were 0.23, 0.26, and 1.25 ms, respectively. Pore sizes less than 11.6 nm indicate unrecoverable fluid, those higher than 88 nm indicate free fluid, and the rest (11.6–88 nm) indicate capillary bound fluid. As the degree of coal metamorphism increases, free fluid saturation decreases, capillary bound fluid saturation increases and then decreases, and unrecoverable fluid saturation increases.

The effect of the inlet steam superheat degree on the non-equilibrium condensation in steam turbine cascade

Due to the high steam velocity and low thermal parameters at the turbine's final stage, steam generates non-equilibrium condensation and forms a large number of small droplets during the process of pressure expansion. The wet steam mixed with droplets impinges on the turbine blades, endangering turbine operation safety and reducing turbine work efficiency. This article modifies the non-equilibrium condensation control equation and embeds it into the numerical simulation software to make the numerical calculation results more accurate. By modifying the inlet steam superheat in the classical experiments, the condensation characteristics of wet steam in Moses–Stein nozzles and Dykas cascades are studied. The results show that increasing inlet superheat can effectively suppress the generation of non-equilibrium condensation and reduce outlet liquid mass fraction. The minimum supercooling temperature of non-equilibrium condensation is only related to the working fluid characteristics (the steam model used in this article is around 20 K). When the inlet superheat of the cascade is large, the rapid condensation region is mainly near the suction surface. In contrast, when the superheat is low, the rapid condensation zone is mainly near the pressure surface. The condensation location is mainly affected by the intensity of internal condensation shock waves in the cascade. Increasing inlet superheat not only increases the shock wave intensity but also decreases the shock wave angle in the passage. When the inlet temperature increases by 20 K, the heat efficiency of the cascade increases by about 1%.

On the magnetohydrodynamic stability of channel flow of Navier–Stokes–Voigt fluid

The linear stability of a pressure-driven channel flow of an electrically conducting Navier–Stokes–Voigt type of the viscoelastic fluid subject to a transverse magnetic field is investigated. The validity of Squire's theorem is proved, and the generalized eigenvalue problem for two-dimensional modes is obtained by adopting the Galerkin method, which is subsequently solved using the QZ-algorithm. Although the base flow retains its Newtonian fluid characteristics, the noticeable influence of the Kelvin–Voigt parameter in conjunction with the Hartmann number on the stability of fluid flow is perceived. Instability is exclusively identified within a specific range of the Kelvin–Voigt parameter, markedly affected by the Hartmann number. Furthermore, closed neutral stability curves arise, indicating the requirement of two values of the Reynolds number to completely assess the linear stability criteria, in contrast to the typical single value observed in the case of Newtonian fluids.

Asymmetric water entry of a wedged grillage structure investigated by CFD-FEM co-simulation

When a ship sails in ocean waves the relative movement between ship and wave is very complex. Slamming of bow or stern structures usually occurs in a manner of asymmetric oblique water entry. This implies that both the deflection angle θ and velocity angle α will likely grow to a large value at the same time. In this study, the hydrodynamics problem associated with the asymmetric and oblique water impact of a three-dimensional wedge is investigated using a partitioned CFD-FEM two-way coupled numerical tool by coupling the commercial software STAR-CCM+ and Abaqus within the framework of SIMULIA co-simulation engine. The hydrodynamic problem is solved by the CFD software using overset grid technique while the structural dynamic response is solved by the FEM software. Validation of the numerical results is conducted by using existing test results of symmetric water entry of the wedge first. Then the behaviours of movements, slamming pressure and structural response of the wedge structure during asymmetric water entry by varying the deflection angle θ or the velocity angle α or both are systematically and comparatively investigated. This research shows that the present numerical simulation well predicts both the fluid and structural dynamic characteristics such as fluid cavity and structural stress concentration of asymmetric impact problems, which has potential engineering application value in the field of ship design and slamming loads evaluation.

Analysis of Magnetohydrodynamic Free Convection in Micropolar Fluids over a Permeable Shrinking Sheet with Slip Boundary Conditions

The convective micropolar fluid flow over a permeable shrinking sheet in the presence of a heat source and thermal radiation with the magnetic field directed towards the sheet has been studied in this paper. The mathematical formulation considers the partial slip condition at the sheet, allowing a realistic representation of the fluid flow near the boundary. The governing equations for the flow, heat, and mass transfer are formulated using the conservation laws of mass, momentum, angular momentum, energy, and concentration. The resulting nonlinear partial differential equations are transformed into a system of ordinary differential equations using suitable similarity transformations. The numerical solutions are obtained using robust computational techniques to examine the influence of various parameters on the velocity, temperature, and concentration profiles. The impact of slip effects, micropolar fluid characteristics, and permeability parameters on the flow features and heat transfer rates are thoroughly analyzed. The findings of this investigation offer valuable insights into the behavior of micropolar fluids in free convection flows over permeable shrinking sheets with slip, providing a foundation for potential applications in various industrial and engineering processes. Key findings include the observation that the velocity profile overshoots for assisting flow with decreasing viscous force and rising magnetic effects as opposed to opposing flow. The thermal boundary layer thickness decreases due to buoyant force but shows increasing behavior with heat source parameters. The present result agrees with the earlier findings for specific parameter values in particular cases.

Neural network architecture to optimize the nanoscale thermal transport of ternary magnetized Carreau nanofluid over 3D wedge

SignificanceIncorporation of nanoparticles in base fluid water is significant for analysis of thermal behavior of nanofluid mixtures, which has various applications in materials science and thermal engineering, and supervised neural scheme predicts the thermal behavior by solving Carreau nanofluid model. MotiveThis article brings the investigation related to prediction of thermal transport of a ternary magnetized hybrid nanofluid [(Al2O3, CuO, TiO2)/H2O] with a three-dimensional Carreau nanofluid model over a wedge. Three nanoparticles dispersed in water (H2O). Inclined magnetic field is considered for judgement of velocity profile and thermal radiation is utilized to scrutinize the temperature distribution of nanofluid. The Carreau mathematical model is chosen to depict the rheological characteristics of non-Newtonian fluids at very high and very low shear rate. MethodologyPhysical assumptions creates the system of Partial differential equations (PDEs) and these are converted into ordinary differential equations (ODEs) by similarity tool. Further ODEs are dealt with bvp4c scheme and further prediction of solution is made by Levenberg-Marquardt neural network (LM-NN) supervised neural scheme. FindingsIncreased volume friction coefficients of nanoparticles increases the transport of heat. High inclined magnetic effect, thermal radiation, pressure gradient and shear strain parameter predict higher thermal transport.

Characteristics of planar buoyant jets and plumes in a turbulent channel crossflow from direct numerical simulations

AbstractThis paper is motivated by an interest in understanding the characteristics of buoyant fluids discharged from the bottom wall of channels, such as encountered during tunnel fires or in river effluent discharge. Direct numerical simulation is used to model the upward release of a planar buoyant jet or plume from the bottom wall of a channel into an incoming turbulent crossflow. The well-studied jet-in-crossflow with only a momentum source is simulated first, and subsequently, fixing the incoming Reynolds number, buoyancy source as heat flux is added alongside varying momentum source, with two cases where only a buoyancy source is present. Appropriate five non-dimensional parameters relevant for this flow are defined, of which three are fixed and two—source to channel momentum ratio and Richardson number—are varied. The changes in turbulence characteristics as the buoyant jet or plume evolves downstream are presented. In all cases with buoyancy, except for the pure jet case, the plume is initially confined to the lower half of the channel before it suddenly lifts to the top half, an effect that occurs at an increasingly smaller downstream distance with increasing buoyancy, and dividing the flow into a near and far field. The distributions of mean and Reynolds stresses in the near and far field of the source are reported, and it is found that the channel flow becomes more turbulent downstream of the source, and further, the turbulent vertical temperature flux switches sign from near to far field owing the a change in the mean temperature gradient sign. From the input parameters and using the integrated temperature equation a reasonable estimate of the far field mean channel temperature can be obtained by a reference temperature based on the heat conservation that includes the convective and diffusive source heat flux. A monotonic behaviour of the back-layering distance is also observed a function of this reference temperature, which was difficult to obtain with the two specified non-dimensional parameters.

Nomogram to Predict the Outcome of Ventriculoperitoneal Shunt Among Patients with Non-HIV Cryptococcal Meningitis

BackgroundThe ventriculoperitoneal (VP) shunt is widely acknowledged as a treatment option for managing intracranial hypertension resulting from non-HIV cryptococcal meningitis (CM). Nonetheless, there is currently no consensus on the appropriate surgical indications for this procedure. Therefore, it is crucial to conduct a preoperative evaluation of patient characteristics and predict the outcome of the VP shunt to guide clinical treatment effectively. MethodsA retrospective analysis was conducted on data from 85 non-HIV CM patients who underwent VP shunt surgery at our hospital. The analysis involved studying demographic data, preoperative clinical manifestations, cerebrospinal fluid (CSF) characteristics, and surgical outcomes and comparisons between before and after surgery. A nomogram was developed and evaluated. ResultsThe therapy outcomes of 71 patients improved, whereas 14 cases had worse outcomes. Age, preoperative cryptococcus count, and preoperative CSF protein levels were found to influence the surgical outcome. The nomogram exhibited exceptional predictive performance (AUC = 0.896, 95% CI: 0.8292–0.9635). Internal validation confirmed the nomogram's excellent predictive capabilities. Moreover, decision curve analysis demonstrated the nomogram's practical clinical utility. ConclusionThe surgical outcome of VP shunt procedures in non-HIV CM patients was associated with age, preoperative cryptococcal count, and preoperative CSF protein levels. We developed a nomogram that can be used to predict surgical outcomes in non-HIV CM patients.

Numerical simulation of fluid-particle flow of jet in supercritical water environment

Supercritical water gasification provides a new approach to the green transformation of coal. Nevertheless, the flow characteristics of fluids and particles injected into the reactor through the nozzle still need to be further investigated. In this paper, a three-dimensional numerical simulation of the particle jet in supercritical water environment is carried out coupling Large Eddy Simulation (LES) with Discrete Phase Model (DPM). The simulation focuses on the effects of particle size, Stokes number, mass flux ratio and initial fluid velocity on the flow characteristic of the fluid-particle flow, especially on the vortex structure evolution, particle distribution and velocity profile. The findings are that as the particle size decreases and the initial fluid velocity increases, the evolution of vortex structures become increasingly fierce, such as the destruction of large-scale coherent structures, the disappearance of vortex ribs, and the lateral expansion of vortices in the development section. Particle distribution exhibits characteristics similar to the vortex structure, as particles adhere closely to the carrier fluid at low Stokes number (St < 1). On the contrary, with increasing of Stokes number (St > 1), the particles are freer from fluid interference and keep their original motion state moving forward. The fluid velocity at the center of the transverse interface jet decrease with increased mass flow ratio. For higher initial fluid velocities, particle distribution is more uniform, and more particles are carried to areas with larger radial distances.

Turk character in the legendary Albanian songs named The Songs of the Frontier Warriors

For a long period of time, the Balkan Peninsula had marked the border between the Ottoman and the Austro-Hungarian empires. The existence of the border at this point meant that in the Balkans there was a part of the population that was under Austro-Hungary and was part of it, but there was also a part of the population that was under the Ottoman Empire and that was part of it. As a result, not only do we find the Turk individual as a character being mentioned in most of the cultures co-existing in the Balkan Peninsula at the time but within a very limited environment we find the latter being presented somewhere as a positive character and somewhere as a negative character. The Songs of the Frontier Warriors is a tremendous literary compilation of Albanian epic songs in which is presented the conflict between the Albanians and the Slavic invaders coming from the north of the country. These songs depict the conflicts that had been brought into the forefront of the relations between the two nations at the border, the wars between them, the imprisonment of one another, property appropriations and kidnapping of girls etc. In a great number of such songs one comes across the Turk as a character. We have analyzed the Turk as a character as mentioned in twenty-five of such songs and in all of them the Turk is presented as a positive character, who helps locals, defends their lands from foreign invaders, protects the locals as well as their families and properties etc. While researching the characteristics of this character in such songs, we have come to underline the fact that there are certain aspects and descriptions of his that are clear and some of which are less clear and ambiguous: the Turk on one hand is clearly depicted as far as his appearance and personality traits are concerned; however, what is deemed as ambiguous in its description is whether by Turksuch songs had referred to the ethnic Turk or the notion of it belongs to a much broader understanding of what a ‘Turk’ is in that it includes all of the population living in the Ottoman Empire. When it comes to its demographics, the Ottoman Empire was a very complex and diverse community reflected by its great number of nations belonging to different religious denominations and speaking different languages living within its borders. This complex demographical diversity only adds to the ambiguity of the name ‘Turk’ as in such songs the latter has not only been used to refer to the Albanian Muslim population, or to the Muslim population in particular but even the people living within the Ottoman Empire’s borders in general. The change highlighted in terms of the status of the character labeled as a ‘Turk’ in different settings and contexts in Albanian epic songs known as the ‘The Songs of the Frontier Warriors’ goes to show that the ‘Turk’ as a character in Albanian folklore is a complex one in that one sees it play a variety of functions making it a very flexible and fluid character in legendary Albanian songs.

Fluid characterization of oil and gas fields: implications for fault and top seal integrity assessment

Integrity of fault and top seal is a key factor that affects hydrocarbon fluid phase distribution in the subsurface. Mapping fluid property distribution can therefore provide important tools towards assessing seal integrity and trapping mechanisms – two of the most critical elements in petroleum systems analysis towards optimzing exploration and development strategies. This is best achieved by proper fluid characterization that integrates fluid geochemistry and pressure–volume–temperature (PVT) data to identify equilibrated and disequilibrated fluid gradients. Fields from Paleozoic and Mesozoic basins in the Arabian Peninsula at different stages of delineation, appraisal, development and management are discussed as examples to demonstrate the role of fluid characterization in aiding the evaluation of top, lateral and fault seal integrity, and in providing insights into the sealing and buffering effects of reservoir heterogeneity on trapping mechanism, fluid distribution and flow capacity. Examples discussed include (1) reservoir heterogeneity controlling fluid distribution and trapping mechanisms in two neighbouring gas fields, (2) geochemical evidence for a lateral seal separating gas condensate region from oil discovered during field development, (3) solid reservoir bitumen atop a giant gas field, (4) selective gas leakage through anhydrite seal, and (5) geochemical evidence for fault-controlled reservoir compartmentalization rather than a hydrodynamically tilted fluid contact in a field at an appraisal stage where PVT data are limited or inconclusive. Put in structural context, seal-related interpretations of the fluid data are aligned with observations from seismic and geological data on the existence of faults with favourable orientations or facies changes. Thematic collection: This article is part of the Fault and top seals 2022 collection available at: https://www.lyellcollection.org/topic/collections/fault-and-top-seals-2022

Numerical Simulation of Hydrodynamics and Mixing Characteristics of High-Viscosity Non-Newtonian Fluid in Twin-Shaft Kneaders

Numerical Simulation of Hydrodynamics and Mixing Characteristics of High-Viscosity Non-Newtonian Fluid in Twin-Shaft Kneaders

Color-switching hydrogels as integrated microfluidic pressure sensors

Precisely measuring pressure in microfluidic flows is essential for flow control, fluid characterization, and monitoring, but faces specific challenges such as achieving sufficient resolution, non-invasiveness, or ease of use. Here, we demonstrate a fully integrated multiplexed optofluidic pressure sensor, entirely decoupled from the flow path, that enables local pressure measurements along any microfluidic channel without altering its flow geometry. The sensor itself relies on the compression of a soft mechano-actuated hydrogel, changing color in response to a pressure change. The hydrogel is separated from the fluid circulating in the channel by a thin membrane, allowing for the unrestricted use of different types of fluids. Imaging the gel through the transparent PDMS with a color camera provides a direct, easy, and contact-free determination of the fluid pressure at the sensing location for pressures as small as 20mbar with a resolution of around 10mbar. The sensitivity and accessible pressure range can be tuned via the mechanical properties of the sensing unit. The photonic gel can also be used to acquire 2D pressure or deformation maps, taking advantage of the fast response time and fine spatial resolution.