Showing papers on "Pressure measurement published in 2013"

Triboelectric Active Sensor Array for Self-Powered Static and Dynamic Pressure Detection and Tactile Imaging

Abstract: We report an innovative, large-area, and self-powered pressure mapping approach based on the triboelectric effect, which converts the mechanical stimuli into electrical output signals. The working mechanism of the triboelectric active sensor (TEAS) was theoretically studied by both analytical method and numerical calculation to gain an intuitive understanding of the relationship between the applied pressure and the responsive signals. Relying on the unique pressure response characteristics of the open-circuit voltage and short-circuit current, we realize both static and dynamic pressure sensing on a single device for the first time. A series of comprehensive investigations were carried out to characterize the performance of the TEAS, and high sensitivity (0.31 kPa–1), ultrafast response time (<5 ms), long-term stability (30 000 cycles), as well as low detection limit (2.1 Pa) were achieved. The pressure measurement range of the TEAS was adjustable, which means both gentle pressure detection and large-scal...

Compressive Sensing Based Machine Learning Strategy For Characterizing The Flow Around A Cylinder With Limited Pressure Measurements

Abstract: Compressive sensing is used to determine the flow characteristics around a cylinder (Reynolds number and pressure/flow field) from a sparse number of pressure measurements on the cylinder. Using a supervised machine learning strategy, library elements encoding the dimensionally reduced dynamics are computed for various Reynolds numbers. Convex L1 optimization is then used with a limited number of pressure measurements on the cylinder to reconstruct, or decode, the full pressure field and the resulting flow field around the cylinder. Aside from the highly turbulent regime (large Reynolds number) where only the Reynolds number can be identified, accurate reconstruction of the pressure field and Reynolds number is achieved. The proposed data-driven strategy thus achieves encoding of the fluid dynamics using the L2 norm, and robust decoding (flow field reconstruction) using the sparsity promoting L1 norm.

High-temperature fiber-optic Fabry–Perot interferometric pressure sensor fabricated by femtosecond laser

Abstract: In this Letter, we report on a fiber-optic Fabry-Perot interferometric pressure sensor with its external diaphragm surface thinned and roughened by a femtosecond laser. The laser-roughened surface helps to eliminate outer reflections from the external diaphragm surface and makes the sensor immune to variations in the ambient refractive index. The sensor is demonstrated to measure pressure in a high-temperature environment with low-temperature dependence.

A highly sensitive pressure sensor using a Au-patterned polydimethylsiloxane membrane for biosensing applications

Abstract: We report on the fabrication and characterization of a highly sensitive pressure sensor using a Au film patterned on a polydimethylsiloxane (PDMS) membrane. The strain-induced change in the film resistance was utilized to perform the quantitative measurement of absolute pressure. The highest sensitivity obtained for a 200 µm thick PDMS film sensor was 0.23/KPa with a range of 50 mm Hg, which is the best result reported so far, over that range, for any pressure sensor on a flexible membrane. The noise-limited pressure resolution was found to be 0.9 Pa (0.007 mm Hg), and a response time of ~200 ms, are the best reported results for these sensors. The ultrahigh sensitivity is attributed to the strain-induced formation of microcracks, the effect of which on the resistance change was found to be highly reversible within a certain pressure range. A physical model correlating the sensitivity with the sensor parameters and crack geometry has been proposed.

Flexible thin-film PVDF-TrFE based pressure sensor for smart catheter applications.

Abstract: We demonstrate the design of thin flexible pressure sensors based on piezoelectric PVDF-TrFE (polyvinyledenedifluoride-tetrafluoroethylene) co-polymer film, which can be integrated onto a catheter, where the compact inner lumen space limit the dimensions of the pressure sensors. Previously, we demonstrated that the thin-film sensors of one micrometer thickness were shown to have better performance compared to the thicker film with no additional electrical poling or mechanical stretching due to higher crystallinity. The pressure sensors can be mass producible using standard lithography process, with excellent control of film uniformity and thickness down to one micrometer. The fabricated pressure sensors were easily mountable on external surface of commercial catheters. Elaborate experiments were performed to demonstrate the applicability of PVDF sensors towards catheter based biomedical application. The resonant frequency of the PVDF sensor was found to be 6.34 MHz. The PVDF sensors can operate over a broad pressure range of 0-300 mmHg. The average sensitivity of the PVDF sensor was found to be four times higher (99 μV/mmHg) than commercial pressure sensor while the PVDF sensor (0.26 s) had fivefold shorter response time than commercial pressure sensor (1.30 s), making the PVDF sensors highly suitable for real-time pressure measurements using catheters.

Soft-matter capacitive sensor for measuring shear and pressure deformation

Abstract: We introduce a soft-matter sensor that measures elastic pressure and shear deformation. The sensor is composed of a sheet of elastomer that is embedded with fluidic parallel-plate capacitors. When the elastomer is pressed or sheared, the electrodes of the embedded capacitors come closer together or slide past each other, respectively, leading to a change in capacitance. The magnitude and direction of the shear deformation is established by comparing the change in capacitance of multiple embedded capacitors. We characterize the soft sensor theoretically and experimentally. Experiments indicate that 2D shear and pressure deformation can be discriminated with approximately 500 μm and 5 kPa sensitivity, respectively. The theoretical predictions and experimental results are in reasonable agreement. We also propose improvements to the fabrication method in order to facilitate integration of soft-matter sensing with wearable electronics.

Evaluation of the pressure field on a rigid body entering a quiescent fluid through particle image velocimetry

Abstract: The objective of this work is to verify the accuracy of indirect pressure measurement from particle image velocimetry in water entry problems. The pressure is evaluated by solving the incompressible Navier–Stokes equations, whose kinematic components are estimated from particle image velocimetry. We focus on the water entry of a rigid wedge, for which we explore variations of the entry velocity. Experimental results are verified through comparison with well-established analytical formulations based on potential flow theory. Our findings demonstrate the feasibility of accurately reconstructing the hydrodynamic pressure field over the entire duration of the impact. Along with a thorough experimental validation of the method, we also offer insight into experimentally relevant factors, such as the maximum resolved fluid velocity and the required spatial integration area.

Underwater Implosion of Cylindrical Metal Tubes

Abstract: The basic physics of the underwater implosion of metal tubes is studied using small scale experiments and finite element simulations. A series of underwater implosion experiments have been conducted with thin-wall aluminum alloy 6061-T6 tubes. The nominal tube dimensions are 2.54 cm outside diameter and 30.48 cm length. Two cylinders collapsed at their natural buckling pressure of 6895 kPa gauge pressure (1000 psig). Two additional cylinders were caused to implode at 6205 kPa gauge pressure (900 psig) using an initiator mechanism. Each of the four cylinders failed with a mode 2 shape (collapsed shape is flat with two lobes). The near field pressure time-history in the water is measured at a radial distance of 10.16 cm (4in.) from the centerline at three points along the cylinder's length. The pressure time-histories show very similar behavior between the cylinders which buckled naturally and those which were mechanically initiated at 90% of the buckling pressure. To aid in understanding the physical implosion phenomena, a computational model is developed with a fluid-structure-interaction finite element code (DYSMAS). This model is validated against the experimental data, and it is used to explain the features of the implosion pressure pulse and how it is physically created.

Compressible fiber optic micro-Fabry-Pérot cavity with ultra-high pressure sensitivity.

Abstract: We propose and demonstrate a pressure sensor based on a micro air bubble at the end facet of a single mode fiber fusion spliced with a silica tube When immersed into the liquid such as water, the air bubble essentially acts as a Fabry-Perot interferometer cavity Such a cavity can be compressed by the environmental pressure and the sensitivity obtained is >1000 nm/kPa, at least one order of magnitude higher than that of the diaphragm-based fiber-tip sensors reported so far The compressible Fabry-Perot interferometer cavity developed is expected to have potential applications in highly sensitive pressure and/or acoustic sensing

A Harsh Environment Wireless Pressure Sensing Solution Utilizing High Temperature Electronics

Abstract: Pressure measurement under harsh environments, especially at high temperatures, is of great interest to many industries. The applicability of current pressure sensing technologies in extreme environments is limited by the embedded electronics which cannot survive beyond 300 °C ambient temperature as of today. In this paper, a pressure signal processing and wireless transmission module based on the cutting-edge Silicon Carbide (SiC) devices is designed and developed, for a commercial piezoresistive MEMS pressure sensor from Kulite Semiconductor Products, Inc. Equipped with this advanced high-temperature SiC electronics, not only the sensor head, but the entire pressure sensor suite is capable of operating at 450 °C. The addition of wireless functionality also makes the pressure sensor more flexible in harsh environments by eliminating the costly and fragile cable connections. The proposed approach was verified through prototype fabrication and high temperature bench testing from room temperature up to 450 °C. This novel high-temperature pressure sensing technology can be applied in real-time health monitoring of many systems involving harsh environments, such as military and commercial turbine engines.

Footcare product dispensing kiosk

Abstract: A kiosk apparatus that may select for a person a recommended footcare product based on pressure measurements collected from pressures sensors or calculated biomechanical data estimates. Pressure measurements and calculated biomechanical data estimates may be used to determine if a foot is unshod on the pressure sensor and also group a person into a classified subgroup. The pressure measurement and calculated biomechanical data estimates may also be used to select a recommended footcare product.

High Sensitivity Force and Pressure Measurements Using Etched Singlemode Polymer Fiber Bragg Gratings

Abstract: Singlemode polymer fiber Bragg gratings (FBGs) are etched down to a diameter of 30 $\mu{\rm m}$ to be used for high sensitivity tensile force measurements. The singlemode polymer fiber and the Bragg gratings are fabricated using the in-house fabrication facility. The fabricated cladding etched polymer FBGs are characterized for low value tensile force measurements and the sensitivity of the sensors is measured and compared with the theoretically estimated values. A sensitivity of 643 nm/N is obtained for the polymer Bragg grating with a diameter of 30 $\mu{\rm m}$ . A pressure sensor based on a singlemode polymer fiber grating is also demonstrated. Low pressure in the range of 290–790 Pa is measured and the observed sensitivity of the pressure sensor is 1.32 pm/Pa. Given the bio-compatible nature of polymer fibers, such as high sensitivity force and pressure sensors can find applications in bio-medical field where high sensitivity low value force/pressure measurements are required.

MEMS Fabry-Perot sensor interrogated by optical system-on-a-chip for simultaneous pressure and temperature sensing

Abstract: We present a micro-electro-mechanical systems (MEMS) based Fabry-Perot (FP) sensor along with an optical system-on-a-chip (SOC) interrogator for simultaneous pressure and temperature sensing. The sensor employs a simple structure with an air-backed silicon membrane cross-axially bonded to a 45° polished optical fiber. This structure renders two cascaded FP cavities, enabling simultaneous pressure and temperature sensing in close proximity along the optical axis. The optical SOC consists of a broadband source, a MEMS FP tunable filter, a photodetector, and the supporting circuitry, serving as a miniature spectrometer for retrieving the two FP cavity lengths. Within the measured pressure and temperature ranges, experimental results demonstrate that the sensor exhibits a good linear response to external pressure and temperature changes.

Continuous in vivo blood pressure measurements using a fully implantable wireless SAW sensor

Abstract: In this paper, the development of a fully implantable wireless sensor able to provide continuous real-time accurate pressure measurements is presented. Surface Acoustic Wave (SAW) technology was used to deposit resonators on crystalline quartz wafers; the wafers were then assembled to produce a pressure sensitive device. Excitation and reading via a miniature antenna attached to the pressure sensor enables continuous external interrogation. The main advantages of such a configuration are the long term stability of quartz and the low power necessary for the interrogation, which allows 24/7 interrogation by means of a hand-held, battery powered device. Such data are of vital importance to clinicians monitoring and treating the effects of hypertension and heart failure. A prototype was designed and tested using both a bio-phantom test rig and an animal model. The pressure traces for both compare very well with a commercially available catheter tip pressure transducer. The work presented in this paper is the first known wireless pressure data from the left ventricle of the heart of a living swine.

Use of radiation pressure for measurement of high-power laser emission.

Abstract: We demonstrate a paradigm in absolute laser radiometry where a laser beam’s power can be measured from its radiation pressure. Using an off-the-shelf high-accuracy mass scale, a 530 W Yb-doped fiber laser, and a 92 kW CO2 laser, we present preliminary results of absolute optical power measurements with inaccuracies of better than 7% to 13%. We find negligible contribution from radiometric (thermal) forces. We also identify this scale’s dynamic-force noise floor for a 0.1 Hz modulation frequency as 4 μN/Hz1/2 or, as optical power sensitivity, 600 W/Hz1/2.

An optical fiber Bragg grating force sensor for monitoring sub-bandage pressure during compression therapy

Abstract: Graduated compression bandaging of the lower limbs is the primary therapy for venous leg ulcers with its efficacy believed to be predominantly dependent on the amount and the distribution of the compressive pressure applied. There has been on-going demand for an ideal sensor to facilitate in-vivo monitoring of the sub-bandage pressure. Several methods and devices have been reported but each has its limitations, such as bulkiness, low tolerance to movement, susceptible to thermal noise and single point sensing. An optical fiber force sensor is demonstrated, consisting of two arrays of fiber Bragg grating (FBG) entwined in a double helix form and packaged with contact-force sensitivity. This sensor array has inherent temperature immunity and is capable of real-time, distributed sensing of sub-bandage pressure. The calibration results of the sensor array, as well as the validation human trial results, are presented.

Incorporation of beams into bossed diaphragm for a high sensitivity and overload micro pressure sensor.

Abstract: The paper presents a piezoresistive absolute micro pressure sensor, which is of great benefits for altitude location. In this investigation, the design, fabrication, and test of the sensor are involved. By analyzing the stress distribution of sensitive elements using finite element method, a novel structure through the introduction of sensitive beams into traditional bossed diaphragm is built up. The proposed configuration presents its advantages in terms of high sensitivity and high overload resistance compared with the conventional bossed diaphragm and flat diaphragm structures. Curve fittings of surface stress and deflection based on ANSYS simulation results are performed to establish the equations about the sensor. Nonlinear optimization by MATLAB is carried out to determine the structure dimensions. The output signals in both static and dynamic environments are evaluated. Silicon bulk micromachining technology is utilized to fabricate the sensor prototype, and the fabrication process is discussed. Experimental results demonstrate the sensor features a high sensitivity of 11.098 μV/V/Pa in the operating range of 500 Pa at room temperature, and a high overload resistance of 200 times overpressure to promise its survival under atmosphere. Due to the excellent performance above, the sensor can be applied in measuring the absolute micro pressure lower than 500 Pa.

CMOS MEMS capacitive absolute pressure sensor

Abstract: This paper presents the design, fabrication and characterization of a capacitive pressure sensor using a commercial 0.18??m CMOS (complementary metal?oxide?semiconductor) process and postprocess. The pressure sensor is capacitive and the structure is formed by an Al top electrode enclosed in a suspended SiO2?membrane, which acts as a movable electrode against a bottom or stationary Al electrode fixed on the SiO2?substrate. Both the movable and fixed electrodes form a variable parallel plate capacitor, whose capacitance varies with the applied pressure on the surface. In order to release the membranes the CMOS layers need to be applied postprocess and this mainly consists of four steps: (1) deposition and patterning of PECVD (plasma-enhanced chemical vapor deposition) oxide to protect CMOS pads and to open the pressure sensor top surface, (2) etching of the sacrificial layer to release the suspended membrane, (3) deposition of PECVD oxide to seal the etching holes and creating vacuum inside the gap, and finally (4) etching of the passivation oxide to open the pads and allow electrical connections. This sensor design and fabrication is suitable to obey the design rules of a CMOS foundry and since it only uses low-temperature processes, it allows monolithic integration with other types of CMOS compatible sensors and IC (integrated circuit) interface on a single chip. Experimental results showed that the pressure sensor has a highly linear sensitivity of 0.14?fF?kPa?1?in the pressure range of 0?300?kPa.

Normal stress measurements in sheared non-Brownian suspensions

Abstract: Measurements in a cylindrical Taylor–Couette device of the shear-induced radial normal stress in a suspension of neutrally buoyant non-Brownian (noncolloidal) spheres immersed in a Newtonian viscous liquid are reported. The radial normal stress of the fluid phase was obtained by measurement of the grid pressure Pg, i.e., the liquid pressure measured behind a grid which restrained the particles from crossing. The radial component of the total stress of the suspension was obtained by measurement of the pressure, Pm, behind a membrane exposed to both phases. Pressure measurements, varying linearly with the shear rate, were obtained for shear rates low enough to insure a grid pressure below a particle size dependent capillary stress. Under these experimental conditions, the membrane pressure is shown to equal the second normal stress difference, N2, of the suspension stress whereas the difference between the grid pressure and the total pressure, Pg−Pm, equals the radial normal stress of the particle phase, Σr...

Study on the parameters influencing the accuracy and reproducibility of dynamic pressure measurements at the surface of a rigid body during water impact

Abstract: Water wave slamming is known as one of the most important load which marine constructions encounter. Especially the large and spiky local pressures moving fast over the body surface during a slamming event can be harmful for the structure. Analytical and numerical research on these pressure loads has already been performed, but however, quantitative experimental information necessary for validation of these studies is restricted. This lack in experimental data may originate from the fact that accurate pressure measurements are difficult to perform. This paper investigates the reason why this type of measurements is so difficult by identifying the parameters affecting the pressure recordings during water impact. According to the authors’ knowledge, no other paper is available in the open literature which investigates all these influencing factors. It has been observed that the pressure signal sampling rate, sensor position, water temperature, object surface conditions and water surface conditions all have an effect on the measured pressures. Only by controlling these parameters, accurate and reproducible results are possible. Precautions in order to meet this goal are formulated.

Optimized MEMS Pirani sensor with increased pressure measurement sensitivity in the fine and rough vacuum regimes

Abstract: An optimized microelectromechanical systems Pirani sensor with increased sensitivity for pressure measurements in the fine and high vacuum regime (from 100 to 10−6 Torr) is presented. Theoretical calculations of the signal voltage as a function of pressure are in good agreement with the measured voltage–pressure response. Fabrication technologies, design optimization using thermal modeling and finite element method simulations, and measurement results are presented.

Self-motion effects on hydrodynamic pressure sensing: part I. Forward–backward motion

Abstract: In underwater locomotion, extracting meaningful information from local flows is as desirable as it is challenging, due to complex fluid-structure interaction. Sensing and motion are tightly interconnected; hydrodynamic signals generated by the external stimuli are modified by the self-generated flow signals. Given that very little is known about self-generated signals, we used onboard pressure sensors to measure the pressure profiles over the head of a fusiform-shape craft while moving forward and backward harmonically. From these measurements we obtained a second-order polynomial model which incorporates the velocity and acceleration of the craft to estimate the surface pressure within the swimming range up to one body length/second (L s−1). The analysis of the model reveals valuable insights into the temporal and spatial changes of the pressure intensity as a function of craft's velocity. At low swimming velocities (<0.2 L s−1) the pressure signals are more sensitive to the acceleration of the craft than its velocity. However, the inertial effects gradually become less important as the velocity increases. The sensors on the front part of the craft are more sensitive to its movements than the sensors on the sides. With respect to the hydrostatic pressure measured in still water, the pressure detected by the foremost sensor reaches values up to 300 Pa at 1 L s−1 swimming velocity, whereas the pressure difference between the foremost sensor and the next one is less than 50 Pa. Our results suggest that distributed pressure sensing can be used in a bimodal sensing strategy. The first mode detects external hydrodynamic events taking place around the craft, which requires minimal sensitivity to the self-motion of the craft. This can be accomplished by moving slowly with a constant velocity and by analyzing the pressure gradient as opposed to absolute pressure recordings. The second mode monitors the self-motion of the craft. It is shown here that distributed pressure sensing can be used as a speedometer to measure the craft's velocity.

An experimental study on SrB4O7:Sm2+ as a pressure sensor

Abstract: A pressure sensor of SrB4O7:Sm2+ has been synthesized and the pressure shift of its 7D0-5F0 fluorescence line has been recalibrated at room temperature up to 48 GPa and 127 GPa hydrostatically and non-hydrostatically, respectively. Different from previous study, our results show that the calibrated relation in the quasi-hydrostatic pressure environment is quite different from that in the non-hydrostatic pressure environment. The yield strength of SrB4O7:Sm2+ as a function of the pressure has been determined by the pressure gradient method in a diamond anvil cell. The results show that the yield strength of SrB4O7:Sm2+ increases from 2.85 GPa at a pressure of 7.9 GPa to 4.22 GPa at 25.4 GPa and is much smaller than that of ruby. The relatively small high-pressure yield strength of SrB4O7:Sm2+ is at the same level of the most sample materials. This would result in a small pressure difference with the coexisting sample, thus lead to a small error in the pressure measurement. The smaller yield strength and excellent fluorescent spectral characters of SrB4O7:Sm2+ make it a good substitute for ruby as a pressure scale in high-pressure experiments, especially under non-hydrostatic pressure environments.

Systematic approach to development of pressure sensors using dielectric electro-active polymer membranes

Abstract: Dielectric electro-active polymers (DEAPs) have become attractive materials for various actuation and sensing applications due to their high energy and power density, high efficiency, light weight, and fast response speed. However, commercial development has been hindered due to a variety of constraints such as reliability, non-linear behavior, cost of driving electronics, and form factor requirements. This paper presents the systematic development from laboratory concept to commercial readiness of a novel pressure sensing system using a DEAP membrane. The pressure sensing system was designed for in-line pressure measurements for low pressure applications such as health systems monitoring. A first generation sensor was designed, built and tested with a focus on the qualitative capabilities of EAP membranes as sensors. Experimental measurements were conducted that demonstrated the capability of the sensor to output a voltage signal proportional to a changing pressure. Several undesirable characteristics were observed during these initial tests such as strong hysteresis, non-linearity, very limited pressure range, and low fatigue life. A second generation prototype was then designed to remove or compensate for these undesirable characteristics. This prototype was then built and tested. The new design showed an almost complete removal of hysteretic non-linear effects and was capable of operating at 10 × the pressure range of the initial generation. This new design is the framework for a novel DEAP based pressure sensor ready for commercial applications.

Metrological Performances of a Plantar Pressure Measurement System

Abstract: Plantar pressure measurements provide useful information to diagnose a diverse range of foot disorders; unfortunately, the commercially available measurement systems are undesirably sensitive to several disturbances, but this aspect is mostly neglected in the literature. This paper describes the results of an experimental campaign aiming at the identification of pressure measuring system metrological performances, at system modeling, and at the implementation of correction procedures. The sensor model was implemented using the results of static and dynamic tests performed on a pedar-X plantar pressure measurement system. The static calibration was performed by analyzing the effect of temperature, single sensor coverage area, local curvature, tangential forces, long-term stability (creep), and sensor crosstalk on the system performances. The dynamic calibration was performed on an electrodynamic shaker, identifying the single sensor frequency response function and the hysteresis under different average loads. The dynamic sensor model is based on the Kelvin-Voigt model, which is representative of the viscoelastic behavior of the material. The model allowed us to compensate both the creep (i.e., the behavior under static loads) and the nonunitary frequency response function. A deconvolution-based algorithm has been proposed to compensate the sensor crosstalk effects, although its implementation requires additional investigations. Experimental results of bobbing and gait tests showed that, with the adoption of the proposed compensation algorithms, the force and center of pressure errors could be reduced by more than 50% of their initial values.

Study of Near Wall Coherent Flow Structures on Dimpled Surfaces Using Unsteady Pressure Measurements

Abstract: Unsteady pressure measurements have been performed inside a spherical dimple in a narrow channel for turbulent flow at ReD = 40,000 with the aim to study coherent vortex structures and to get a deep insight into flow physics. Results confirm the formation of asymmetric coherent vortex structures switching between two extreme positions. Analysis of the pressure temporal distributions and correlation functions shows the presence of the anti-phase motion inside the dimple. Typical power laws of the pressure fluctuation energy spectrum ω − 1 and ω − 7/3 are reproduced.