Shear Stress Sensor Research Articles

Design and Manufacturing of Shear Stress Sensor for High-Temperature Applications With Embedded Capacitive Floating Unit

Design and Manufacturing of Shear Stress Sensor for High-Temperature Applications With Embedded Capacitive Floating Unit

EPHB4-RASA1 Inhibition of PIEZO1 Ras Activation Drives Lymphatic Valvulogenesis.

EPHB4 (ephrin receptor B4) and the RASA1 (p120 Ras GTPase-activating protein) are necessary for the development of lymphatic vessel (LV) valves. However, precisely how EPHB4 and RASA1 regulate LV valve development is unknown. In this study, we examine the mechanisms by which EPHB4 and RASA1 regulate the development of LV valves. We used LV-specific inducible EPHB4-deficient mice and EPHB4 knockin mice that express a form of EPHB4 that is unable to bind RASA1 yet retains protein tyrosine kinase activity (EPHB4 2YP) to study the role of EPHB4 and RASA1 in LV valve development in the embryo and LV valve maintenance in adults. We also used human dermal lymphatic endothelial cells in vitro to study the role of EPHB4 and RASA1 as regulators of LV valve specification induced by oscillatory shear stress, considered the trigger for LV valve specification in vivo. LV valve specification, continued valve development postspecification, and LV valve maintenance were blocked upon induced loss of EPHB4 in LV. LV valve specification and maintenance were also impaired in EPHB4 2YP mice. Defects in LV valve development were reversed by inhibition of the Ras-MAPK (mitogen-activated protein kinase) signaling pathway. In human dermal lymphatic endothelial cells, loss of expression of EPHB4 or its ephrin b2 ligand, loss of expression of RASA1, and inhibition of physical interaction between EPHB4 and RASA1 resulted in dysregulated oscillatory shear stress-induced Ras-MAPK activation and impaired expression of LV specification markers that could be rescued by Ras-MAPK pathway inhibition. The same results were observed when human dermal lymphatic endothelial cells were stimulated with the Yoda1 agonist of the PIEZO1 oscillatory shear stress sensor. Although Yoda1 increased the number of LV valves when administered to wild-type embryos, it did not increase LV valve number when administered to EPHB4 2YP embryos. EPHB4 is necessary for LV valve specification, continued valve development postspecification, and valve maintenance. LV valve specification requires physical interaction between EPHB4 and RASA1 to limit activation of the Ras-MAPK pathway in lymphatic endothelial cells. Specifically, EPHB4-RASA1 physical interaction is necessary to dampen Ras-MAPK activation induced through the PIEZO1 oscillatory shear stress sensor. These findings reveal the mechanism by which EPHB4 and RASA1 regulate the development of LV valves.

Low or oscillatory shear stress and endothelial permeability in atherosclerosis.

Endothelial shear stress is a tangential stress derived from the friction of the flowing blood on the endothelial surface of the arterial wall and is expressed in units of force/unit area (dyne/cm2). Branches and bends of arteries are exposed to complex blood flow patterns that generate low or oscillatory endothelial shear stress, which impairs glycocalyx integrity, cytoskeleton arrangement and endothelial junctions (adherens junctions, tight junctions, gap junctions), thus increasing endothelial permeability. The lipoproteins and inflammatory cells penetrating intima due to the increased endothelial permeability characterizes the pathological changes in early stage of atherosclerosis. Endothelial cells are critical sensors of shear stress, however, the mechanisms by which the complex shear stress regulate endothelial permeability in atherosclerosis remain unclear. In this review, we focus on the molecular mechanisms of the endothelial permeability induced by low or oscillatory shear stress, which will shed a novel sight in early stage of atherosclerosis.

Wind-Tunnel-in-the-Loop Exploration and Optimization of Active Flow Control Parameters

This paper considers the use of surrogate-based analysis and optimization (SBAO) methods to investigate the performance of pulsed jet actuators for active separation control in a wind tunnel. Two experimental setups are examined: pressure-induced separation on a one-sided diffuser and trailing-edge separation on a NACA 64A-015 airfoil. In both cases the modeling is done using Gaussian process regression (kriging), and the investigated active-flow-control parameters are the amplitude, frequency, and duty cycle of the actuators that are used to mitigate boundary-layer separation. In the diffuser test case, a parameter-space exploration is conducted to examine the effect of the three input parameters on the amount of reverse flow detected by an array of calorimetric shear-stress sensors. In the airfoil test case, an optimization strategy is followed to maximize an objective function constructed with the airfoil sectional lift coefficient and the mass flow consumption of the actuators. Both experiments consistently indicate that lowering the duty cycle of the pulsed-jet actuators below 0.5 may lead to efficiency gains in active separation control by limiting their mass flow consumption for equal performance, but with a concomitant supply pressure increase. Overall, the results presented herein demonstrate that SBAO methods could provide a potential for more efficient wind tunnel investigations involving multiparameter problems.

Response and resilience of carbon nanotube micropillars to shear flow

Interactions between carbon nanotubes (CNTs) and fluid flows are central to the operation of several emerging nanotechnologies. In this paper, we explore the fluid-structure interaction of CNT micropillars in wall-bounded shear flows, relevant to recently developed microscale wall shear stress sensors. We monitor the deformation of CNT micropillars in channel flow as the flow rate and wall shear stress are gradually varied. We quantify how the micropillars bend at low wall shear stress, and then will commonly tilt abruptly from their base above a threshold wall shear stress, which is attributed to the lower density of the micropillars in this region. Some micropillars are observed to flutter rapidly between a vertical and horizontal position around this threshold wall shear stress, before settling to a tilted position as wall shear stress increases further. Tilted micropillars are found to kink sharply near their base, similar to the observed buckling near the base of CNT micropillars in compression. Upon reducing the flow rate, micropillars are found to fully recover from a near horizontal position to a near vertical position, even with repeated on-off cycling. At sufficiently high wall shear stress, the micropillars were found to detach at the catalyst particle-substrate interface. The mechanical response of CNT micropillars in airflow revealed by this study provides a basis for future development efforts and the accurate simulation of CNT micropillar wall shear stress sensors.

Cell-based shear stress sensor for bioprocessing

Shear stress during bioreactor cultivation has significant impact on cell health, growth, and fate. Mammalian cells, such as T cells and stem cells, in next-generation cell therapies are especially more sensitive to shear stress present in their culture environment than bacteria. Therefore, a base knowledge about the shear stress imposed by the bioprocesses is needed to optimize the process parameters and enhance cell growth and yield. However, typical computational flow dynamics modeling or PCR-based assays have several limitations. Implementing and interpreting computational modeling often requires technical specialties and also relies on many simplifications in modeling. PCR-based assays evaluating changes in gene expression involve cumbersome sample preparation with the use of advanced lab equipment and technicians, hampering rapid and straightforward assessment of shear stress. Here, we developed a simple, cell-based shear stress sensor for measuring shear stress levels in different bioreactor types and operating conditions. We engineered a CHO-DG44 cell line to make its stress sensitive promoter EGR-1 control GFP expression. Subsequently, the stressed CHO cells were transferred into a 96 well plate, and their GFP levels (population mean fluorescence) were monitored using a cell analysis instrument (Incucyte®, Sartorius Stedim Biotech) over 24 hours. After conducting sensor characterization, which included chemical induced stress and fluid shear stress, and stability investigation, we tested the shear stress sensor in the Ambr® 250 bioreactor vessels (Sartorius Stedim Biotech) with different impeller and vessel designs. The results showed that the CHO cell-based shear stress sensors expressed higher GFP levels in response to higher shear stress magnitude or exposure time. These sensors are useful tools to assess shear stress imposed by bioreactor conditions and can facilitate the design of various bioreactor vessels with a low shear stress profile.

An Ultrathin and Fast Response Flexible Shear Stress Sensor with Improved Thermal Efficiency

An Ultrathin and Fast Response Flexible Shear Stress Sensor with Improved Thermal Efficiency

Novel 3D printed capacitive shear stress sensor

Novel 3D printed capacitive shear stress sensor

Measurement of Skin Friction in the University of Texas at Arlington Arcjet

Arcjet flows are known to have significant uncertainties associated with the fundamental flow quantities. A detailed characterization is critical to augment the current understanding of these complex flows as well as developing, screening, and qualifying thermal protection systems. Classically, estimations of skin friction have been made indirectly using heat flux analogies. These techniques, however, are marred by high levels of measurement uncertainty and require a priori assumptions about the flowfield. Directly measuring the wall shear stress removes the demand for these assumptions. A direct measurement of shear stress in supersonic high-enthalpy flow at the Office of Naval Research/University of Texas at Arlington arcjet facility has been conducted. The measured wall shear stress was (average combined calibration uncertainty), which matches well with estimations for laminar flow. Two shear stress sensors separated by a distance of 1.905 cm (0.75 in.) were integrated into a 20 deg half-angle shear-wedge platform. The two sensors tracked together within 10% of each other, implying a uniform flowfield over the region studied. Approximately 1.5 s into the test window, a steady increase in skin friction was observed. The cause of this nonphysically accurate increase in the shear stress measurement is discussed.

Application of sine cosine algorithm-support vector regression on temperature compensation of MEMS shear stress sensor

Application of sine cosine algorithm-support vector regression on temperature compensation of MEMS shear stress sensor

Design and fabrication of non-resonant PZT MEMS micromirror with buried piezoresistors for closed loop position control

This paper reports on a 1D PZT micromirror integrated with buried piezoresistors for quasi-static feedback position control. The piezoresistors located along or below the PZT actuators could achieve the sensitivity as high as 3.1 mV/°, which was two orders of magnitude higher than the traditional ones located at the torsion springs (8.2 μV/°). This increased the signal-to-noise ratio by 2 orders of magnitude, which could enable the accurate position control. The response of the longitudinal sensors along the beams had a fast settling time less than 1 ms. The average position error was 0.975%, which was much better than that from the conventional shear stress sensor on the torsion bar of 3.1%.

Surrogate-based parameter exploration for the design of MEMS calorimetric wall shear stress sensors by means of CFD

A family of MEMS calorimetric wall shear stress sensors is experimentally and numerically investigated to determine their most significant design parameters. Fifteen sensor prototypes are first calibrated in a range of ± 2 Pa to generate an experimental database for validation of the subsequent numerical investigation. Then, a fully parameterized numerical setup is used to investigate the effect of three geometric design parameters, namely the cavity height, the cavity width, and the inter-beam distance, on amplitude and sensitivity of the sensor. This is done by building a surrogate model based on Gaussian Process interpolation (Kriging) in the four-dimensional space consisting of the three design parameters and the shear velocity in the flow. Thanks to this methodology, the calibration curves of all possible sensor designs in the investigated range can be estimated with an error of less than 2 %. A detailed study of this model reveals that the most significant design parameters are the inter-beam distance and the cavity width, while the cavity height is found to be of minor importance. • CFD Simulation of MEMS calorimetric wall shear stress sensor. • Static calibration of a family of 15 sensors in the range ±2 Pa. • Surrogate-based parameter space exploration of three design parameter. • Interpolation of sensor’s signal and sensitivity for all sensors in defined limits.

Distributed viscosity and flow velocity measurements using a fiber-optic shear stress sensor

The understanding and precise prediction of fluid and solid displacement is of great interest in many technical applications. Density and viscosity are two key parameters that govern process mechanisms. The possibility to measure transient processes over longer distances is desirable. We present a novel distributed shear stress sensor that allows to derive fluid rheological parameters such as the viscosity along a fiber-optic cable being exposed to a moving medium. This works because flow velocity and fluid viscosity directly translate to a shear stress and consequently to a tensile strain on the fiber optic cable. Using the technology of fiber-optic distributed strain sensing, strain changes (and temperatures) are detected in real-time at any location along the fiber. Given the cable mechanical properties and geometry of the flow path, the strain translates to a shear stress which can be correlated to either the flow velocity or fluid viscosity. We derive a theoretical characterization of the sensor based on the principles of fluid mechanics. Also, we perform laboratory experiments with the sensor and demonstrate that we can distinguish differences of 1 mPa s dynamic viscosities in a range as low as 1 – 7 mPa s. In the next phase, we are implementing this sensor into a real working environment in a wellbore application to investigate the applicability of this novel sensor technology.

Design of readout circuit for high sampling miniaturized MEMS wall shear force sensor

Wall shear stress is one of the important measurement parameters in wind tunnel experiments. In the shock wind tunnel, the duration of the flow field is very short, usually a few milliseconds. To ensure measurement accuracy, the sampling rate should not be less than 1kHz. Due to the limitation of model volume and experimental environment, it is necessary to design a miniaturized readout circuit with high precision and high sampling rate, which is highly integrated with the MEMS wall shear stress sensor. The circuit includes a micro capacitance detection module integrated with the sensor head and a host computer signal processing and display module. Aiming at the complex measurement environment of the shock tunnel, to ensure the measurement accuracy, stability, and anti-interference ability of the weak capacitance detection circuit, a miniaturized ceramic substrate circuit is fabricated by a microstrip circuit process. The test results show that the resolution of the micro capacitance of the circuit can reach 20fF at the detection frequency of 3kHz, which can meet the measurement requirements of Shock tunnel, and realize the real-time measurement and display of wall shear stress signal.

Rapid shear stress-dependent ENaC membrane insertion is mediated by the endothelial glycocalyx and the mineralocorticoid receptor

The contribution of the shear stress-sensitive epithelial Na+ channel (ENaC) to the mechanical properties of the endothelial cell surface under (patho)physiological conditions is unclear. This issue was addressed in in vivo and in vitro models for endothelial dysfunction. Cultured human umbilical vein endothelial cells (HUVEC) were exposed to laminar (LSS) or non-laminar shear stress (NLSS). ENaC membrane insertion was quantified using Quantum-dot-based immunofluorescence staining and the mechanical properties of the cell surface were probed with the Atomic Force Microscope (AFM) in vitro and ex vivo in isolated aortae of C57BL/6 and ApoE/LDLR-/- mice. Flow- and acetylcholine-mediated vasodilation was measured in vivo using magnetic resonance imaging. Acute LSS led to a rapid mineralocorticoid receptor (MR)-dependent membrane insertion of ENaC and subsequent stiffening of the endothelial cortex caused by actin polymerization. Of note, NLSS stress further augmented the cortical stiffness of the cells. These effects strongly depend on the presence of the endothelial glycocalyx (eGC) and could be prevented by functional inhibition of ENaC and MR in vitro endothelial cells and ex vivo endothelial cells derived from C57BL/6, but not ApoE/LDLR-/- vessel. In vivo In C57BL/6 vessels, ENaC- and MR inhibition blunted flow- and acetylcholine-mediated vasodilation, while in the dysfunctional ApoE/LDLR-/- vessels, this effect was absent. In conclusion, under physiological conditions, endothelial ENaC, together with the glycocalyx, was identified as an important shear stress sensor and mediator of endothelium-dependent vasodilation. In contrast, in pathophysiological conditions, ENaC-mediated mechanotransduction and endothelium-dependent vasodilation were lost, contributing to sustained endothelial stiffening and dysfunction.

Reduction of skin friction and two-phase flow structure beneath wall in horizontal rectangular channel

From the viewpoint of the improvement of the air lubrication method for the ship's hull resistance reduction, an experimental study was conducted for two-phase flow in a horizontal rectangular channel with a length of 3.0 m, a gap of 0.05 m, and a width of 0.2 m, which simulates the external two-phase flow. The database on frictional drag and local two-phase flow parameters, including void fraction profile and gas chord length, was collected using a shear stress sensor and a double sensor probe. Measurement of two-phase flow structure was performed at three axial positions of z = 0.930, 1.43, and 1.93 m from the bubble injection port. The wall shear stress was obtained at z = 1.93 m. A total of 72 datasets are acquired a room temperature and at flow conditions of superficial liquid velocity <jf> ranging from 0.832 to 3.00 m/s and superficial gas velocity <jg> ranging from 0.0232 to 0.714 m/s. The effects of entry length, liquid and gas flow rates on the phase distribution characteristics beneath the wall were discussed. The bubble layer thickness was newly defined as the length scale. The bubble layer thickness was not so sensitive to the changes in the liquid flow rates and the entry length, and highly dependent on the gas flow rates in the present experimental conditions. The mean void fraction in the bubble layer was highly reliant on the liquid flow rate and decreased with the superficial liquid velocity. In contrast, the insignificant effect of gas flow rate on the mean void fraction was confirmed. A strong correlation between the drag reduction effect due to the air lubrication and the mean void fraction in the bubble layer was confirmed. The obtained data are expected to be used for the modeling of the interfacial area transport terms, development of the constitutive equations of the drift flux model, modeling of the drag reduction for the external two-phase flow and the benchmark tests of various CFD codes in the future study.

Live 3D imaging and mapping of shear stresses within tissues using incompressible elastic beads.

To investigate the role of mechanical constraints in morphogenesis and development, we have developed a pipeline of techniques based on incompressible elastic sensors. These techniques combine the advantages of incompressible liquid droplets, which have been used as precise in situ shear stress sensors, and of elastic compressible beads, which are easier to tune and to use. Droplets of a polydimethylsiloxane mix, made fluorescent through specific covalent binding to a rhodamin dye, are produced by a microfluidics device. The elastomer rigidity after polymerization is adjusted to the tissue rigidity. Its mechanical properties are carefully calibrated in situ, for a sensor embedded in a cell aggregate submitted to uniaxial compression. The local shear stress tensor is retrieved from the sensor shape, accurately reconstructed through an active contour method. In vitro, within cell aggregates, and in vivo, in the prechordal plate of the zebrafish embryo during gastrulation, our pipeline of techniques demonstrates its efficiency to directly measure the three dimensional shear stress repartition within a tissue.

Spectral Proper Orthogonal Decomposition of Unsteady Wall Shear Stress Under a Turbulent Separation Bubble

Spectral proper orthogonal decomposition (SPOD) is used to investigate the low-frequency behavior of a pressure-induced turbulent separation bubble (TSB) generated on a one-sided diffuser at a nominal velocity of 20 m/s. The input to the decomposition is the unsteady wall shear stress determined experimentally with an array of novel calorimetric shear-stress sensors. The SPOD spectrum indicates low-rank behavior for frequencies below 10 Hz, which correspond to Strouhal numbers when built with the average TSB length and the nominal incoming velocity. A low-order model constructed with only the first SPOD mode at each frequency up to 10 Hz reveals that the TSB is contracting and expanding in a manner reminiscent of the low-frequency breathing motion recently documented in other TSBs. A comparison between SPOD and space-only proper orthogonal decomposition (POD) indicates that both decompositions are able to capture the low-frequency breathing motion as long as space-only POD is applied on signals previously low-pass filtered at 10 Hz. However, the superiority of SPOD is revealed by its inherent capacity to express the frequency range amenable to low-rank behavior. In addition to offering new insights into the low-frequency dynamics of TSBs, the present results also demonstrate the usefulness of calorimetric shear-stress sensors for the study of turbulent separating and reattaching flows.

Epithelial Na+ channel and the glycocalyx: a sweet and salty relationship for arterial shear stress sensing.

The ability of endothelial cells to sense mechanical force, and shear stress in particular, is crucial for normal vascular function. This relies on an intact endothelial glycocalyx that facilitates the production of nitric oxide (NO). An emerging arterial shear stress sensor is the epithelial Na+ channel (ENaC). This review highlights existing and new evidence for the interdependent activity of the glycocalyx and ENaC and its implications for vascular function. New evidence suggests that the glycocalyx and ENaC are physically connected and that this is important for shear stress sensing. The connection relies on N-glycans attached to glycosylated asparagines of α-ENaC. Removal of specific N-glycans reduced ENaC's shear stress response. Similar effects were observed following degradation of the glycocalyx. Endothelial specific viral transduction of α-ENaC increased blood pressure (∼40 mmHg). This increase was attenuated in animals transduced with an α-ENaC version lacking N-glycans. These observations indicate that ENaC is connected to the glycocalyx and their activity is interdependent to facilitate arterial shear stress sensation. Future research focusing on how N-glycans mediate this interaction can provide new insights for the understanding of vascular function in health and disease.

Experimental Results of Local Shear Stresses and Friction Torque in an Open Rotor-Stator Disk System

Abstract This contribution presents experimental investigations of friction torque in an open rotor–stator disk system by using two different measuring procedures. The first procedure is based on a thermo electrical wall shear stress sensor. The sensor is investigated in two different substrates and different measuring parameters. A thermal model consisting of the supplied heating power, the thermal resistance toward the fluid, and into the substrate as well as the over temperature is used to achieve the heat transfer coefficient on the sensor surface. This heat transfer coefficient is attributed by a functional relationship to the wall shear stress. This relationship is first calibrated in a rectangular channel and subsequently validated at a fully turbulent flat plat flow. The second measuring procedure based on the tangential displacement of the stator disk due the friction torque. The disk is attached at a torsion spring. The friction torque is achieved by the torsion spring constant and the tangential displacement of the stator disk. Both measuring procedures are compared and agree well with each other. The used test rig has the possibility of reaching rotational Reynolds numbers representative, for instance, of a modern gas turbine. The investigations were carried out by a 0.5 m diameter rotor disk rotating up to 8500 rpm with a gap ratio between 0.008 and 0.04. The friction torque is measured on the stator disk and can be converted into moment coefficient. Moment coefficient on stator and measured pressure distributions are presented for different gap ratios and rotational Reynolds number.