Optical Pressure Sensor Research Articles

Intracochlear pressure measurements during acoustic shock wave exposure

IntroductionInjuries to the peripheral auditory system are among the most common results of high intensity impulsive acoustic exposure. Prior studies of high intensity sound transmission by the ossicular chain have relied upon measurements in animal models, measurements at more moderate sound levels (i.e. < 130 dB SPL), and/or measured responses to steady-state noise. Here, we directly measure intracochlear pressure in human cadaveric temporal bones, with fiber optic pressure sensors placed in scala vestibuli (SV) and tympani (ST), during exposure to shock waves with peak positive pressures between ∼7 and 83 kPa. MethodsEight full-cephalic human cadaver heads were exposed, face-on, to acoustic shock waves in a 45 cm diameter shock tube. Specimens were exposed to impulses with nominal peak overpressures of 7, 28, 55, & 83 kPa (171, 183, 189, & 192 dB pSPL), measured in the free field adjacent to the forehead. Specimens were prepared bilaterally by mastoidectomy and extended facial recess to expose the ossicular chain. Ear canal (EAC), middle ear, and intracochlear sound pressure levels were measured with fiber-optic pressure sensors. Surface-mounted sensors measured SPL and skull strain near the opening of each EAC and at the forehead. ResultsMeasurements on the forehead showed incident peak pressures approximately twice that measured by adjacent free-field and EAC entrance sensors, as expected based on the sensor orientation (normal vs tangential to the shock wave propagation). At 7 kPa, EAC pressure showed gain, calculated from the frequency spectra, consistent with the ear canal resonance, and gain in the intracochlear pressures (normalized to the EAC pressure) were consistent with (though somewhat lower than) previously reported middle ear transfer functions. Responses to higher intensity impulses tended to show lower intracochlear gain relative to EAC, suggesting sound transmission efficiency along the ossicular chain is reduced at high intensities. Tympanic membrane (TM) rupture was observed following nearly every exposure 55 kPa or higher. ConclusionsIntracochlear pressures reveal lower middle-ear transfer function magnitudes (i.e. reduced gain relative to the ear canal) for high sound pressure levels, thus revealing lower than expected cochlear exposure based on extrapolation from cochlear pressures measured at more moderate sound levels. These results are consistent with lowered transmissivity of the ossicular chain at high intensities, and are consistent with our prior report measuring middle ear transfer functions in human cadaveric temporal bones with high intensity tone pips.

Towards maximizing the sensing accuracy of an cuffless, optical blood pressure sensor using a high-order front-end filter

A high-order filter as part of an analog front-end circuit for an optical, cuffless photoplethysmography (PPG) sensor is developed herein to maximize the sensing accuracy of measured blood pressures (BPs). The BP device consists physically of light emitting diodes and photo-diodes (PDs) to sense the dynamic change of intravascular blood volume based on the known principle of PPG and then calculate the BP based on reflective pule transient time in a PPG signal. The photoplethysmography (PPG) signal acquired by the PDs are expected to be processed by an excellent front-end circuitry to reduce its noise and DC offset but without much distortion to obtain accurate BP prediction. This front-end is accomplished herein by a transimpedance amplifier, a critical high-order band-pass filter and a programmable gain amplifier, which is followed by microprocessor and a wireless module. The band-pass filter is optimized with a passband from 0.2 to 7.2 Hz, where the low-pass is in a 4th order while the high-pass is in 2nd order. The low-pass is designed for reducing noise including those due to ambient lighting, while the high-pass is for reducing DC drifting caused mainly by breathing and/or subject slow motion. 46 subjects were tested with the designed high-order filters in comparison with reference device. The advantages of employing high-order low-pass filter versus first-order is clearly seen in experimental data with an accuracy on predicting BP reaching ±3 mmHg, as stopped to ±7 mmHg using commonly used first-order filters.

Optical Interferometric Pressure Sensor Based on a Buckled Beam With Low-Temperature Cross-Sensitivity

This paper reports a novel optical interferometric sensor based on a buckled beam for pressure measurements with low-temperature dependence. The working principle of the pressure sensor involves a pressure transfer mechanism and a displacement transfer mechanism. The principal sensor structure consists of an optical fiber, a gold-coated steel beam, and a steel sheet with a thickness of 0.8 mm. The optical fiber endface and the center part of the buckled beam form a Fabry–Perot interferometer. When the sensor is subjected to an external pressure, the steel sheet will deflect, resulting in an axial displacement of the prebuckled beam. The axial displacement will be further transferred and amplified to a vertical deflection at the center of the buckled beam, leading to a relatively large change in the Fabry–Perot cavity length. Based on this buckled beam structure, the pressure measurement sensitivity of the novel sensor is improved. Moreover, the sensitivity could be flexibly adjusted through the modification of the initial setting of the buckled beam. In our prototype sensor, a pressure sensitivity of 169 nm/kPa was realized with a low-temperature dependence of 0.022 kPa/°C. The stability of the sensor was also investigated. This cost-effective and easy-to-manufacture sensor is believed to be an excellent candidate for monitoring the environmental pressure in various fields.

Size effect of optical silica microsphere pressure sensors

Two types of optical pressure sensors with silica microspheres are proposed. The size effect of optical silica microsphere pressure sensors is studied by using a single-wavelength laser beam and polarimeters. The silica microspheres with diameters of 1.0 μm, 1.5 μm and 2.0 μm are prepared on garnet substrates by a self-assembly method. The pressure and the optical properties of the silica microspheres are measured by a resistance strain sensor and Thorlabs Stokes polarimeters as a function of the external direct current (DC) voltage. The optical silica microsphere sensor in transmission mode is suitable for pressure measuring. The results show that the pressure increases, while the diameter of the silica microspheres decreases. The maximum internal pressure can reach up to 7.3 × 107 Pa when the diameter of the silica microspheres is 1.0 μm.

Cost-effective optical fiber pressure sensor based on intrinsic Fabry-Perot interferometric micro-cavities

Abstract In this work, a cost-effective procedure to manufacture optical fiber pressure sensors is presented. This has a high relevance for integration in robotic exoskeletons or for gait plantar pressure monitoring within the physical rehabilitation scenarios, among other applications. The sensing elements are based on Fabry-Perot interferometric (FPI) micro-cavities, created from the recycling of optical fibers previously destroyed by the catastrophic fuse effect. To produce the pressure sensors, the fiber containing the FPI micro-cavities was embedded in an epoxy resin cylinder used as pressure transducer and responsible to transfer the pressure applied on its surface to the optical fiber containing the FPI micro-cavity. Before the embedding process, some FPI sensors were also characterized to strain variations. After that, the effect of the encapsulation of the FPI structure into the resin was assessed, from which a slight decrease on the FPI interferogram fringes visibility was verified, indicating a small increase in the micro-cavity length. Up on the sensors characterization, a linear dependence of the wavelength shift with the induced pressure was obtained, which leads to a maximum sensitivity of 59.39 ± 1.7 pm/kPa. Moreover, direct dependence of the pressure sensitivity with the micro-cavity volume and length was found.

Optical fiber tip interferometer gas pressure sensor based on anti-resonant reflecting guidance mechanism

Abstract We propose and demonstrate a gas pressure sensor based on an anti-resonant reflecting guidance (ARRG) mechanism in quartz capillary tube with an open cavity. The device is simple in fabrication by only fusion splicing a segment of capillary tube with single mode fiber. It has compact size, robust structure, convenient mode of operation, and high sensitivity of 4.278 nm/MPa. Moreover, as two Faby-Perot cavities exist in the device, which create the interference spectrum with several distinct resonance dips, a simultaneous gas pressure and temperature detection can be readily achieved by tracing two dip wavelengths. The error in the measurement due to the choice of different resonant dips can be effectively reduced by using the Fourier band pass filtering method.

In-fiber integrated gas pressure sensor based on a hollow optical fiber with two cores

We demonstrate an in-fiber integrated highly-sensitive gas pressure sensor based on a special designed hollow eccentric twin-core optical fiber (HTCF). In this design, the core in the hole and the core in the annular cladding of the HTCF are separately used as sensing arm and reference arm. Then, in-fiber gas pressure detection can be first realized in the long hole of the HTCF. The experimental results show that the sensor exhibits a gas pressure sensitivity of 0.42 nm/bar, with low temperature sensitivity of −51 pm/℃, and a maximum bending sensitivity of 98 pm/μm. Comparing with traditional optical fiber gas pressure sensors, this device first realizes in-fiber gas pressure detecting through the special designed optical fiber with a compact size which can be easily connected and integrated in practical applications.

High pressure luminescence of Nd3+ in YAlO3 perovskite nanocrystals: A crystal-field analysis.

Pressure-induced energy blue- and red-shifts of the 4F3/2 → 4I9/2,11/2 near-infrared emission lines of Nd3+ ions in YAlO3 perovskite nano-particles have been measured from ambient conditions up to 29 GPa. Different positive and negative linear pressure coefficients have been calibrated for the emission lines and related to pressure-induced changes in the interactions between those Nd3+ ions and their twelve oxygen ligands at the yttrium site. Potentiality of the simple overlap model, combined with ab initio structural calculations, in the description of the effects of these interactions on the energy levels and luminescence properties of the optically active Nd3+ ion is emphasized. Simulations show how the energies of the 4f3 ground configuration and the barycenters of the multiplets increase with pressure, whereas the Coulomb interaction between f-electrons decreases and the crystal-field strength increases. All these effects combined explain the wavelength blue-shifts of some near-infrared emission lines of Nd3+ ions. Large pressure rates of various emission lines suggest that a YAlO3 perovskite nano-crystal can be a potential candidate for near-infrared optical pressure sensors.

Manufacturing a Micro-model with Integrated Fibre Optic Pressure Sensors

The measurement of fluid pressure inside pores is a major challenge in experimental studies of two-phase flow in porous media. In this paper, we describe the manufacturing procedure of a micro-model with integrated fibre optic pressure sensors. They have a circular measurement window with a diameter of 260 upmu hbox {m}, which enables the measurement of pressure at the pore scale. As a porous medium, we used a PDMS micro-model with known physical and surface properties. A given pore geometry was produced following a procedure we had developed earlier. We explain the technology behind fibre optic pressure sensors and the procedure for integrating these sensors into a micro-model and demonstrate their utility for the measurement of pore pressure under transient two-phase flow conditions. Finally, we present and analyse results of single and two-phase flow experiments performed in the micro-model and discuss the link between small-scale fast pressure changes with pore-scale events.

Интегрально-оптический датчик давления

The study of a first prototype of an integrated optical pressure sensor based on a ring resonator was presented in the paper. A photopolymer 3D printing method was used for producing of submount (sensor constructive base). This submout has a cavity with reference pressure. We mounted the sensitive element on this submount. The silicon chip with waveguides based on Si 3 N 4 / SiO 2 was used as a sensitive element. A theoretical model of an integrated optical pressure sensor was presented in this paper. Computer calculation model was built based on this theoretical model and a sensitivity of the integrated optical pressure sensor was calculated. A hydraulic comparative calibration system was used for investigation of the sensor properties. A pressure was changed step by step during the experiment and an optical output signal was fixed on every step. As a result a set of spectra was obtained. This set made it possible to calculate the sensitivity of the sensor. The experimental sensitivity of the sensor is different from the calculated one. This may be because the calculation model didn’t take into account the change of a refractive index of waveguides. In addition, this difference may be due to the temperature drift of an optical ring resonator spectrum.

Low Cost Plastic Optical Fiber Pressure Sensor Embedded in Mattress for Vital Signal Monitoring.

The aim of this paper is to report the design of a low-cost plastic optical fiber (POF) pressure sensor, embedded in a mattress. We report the design of a multipoint sensor, a cheap alternative to the most common fiber sensors. The sensor is implemented using Arduino board, standard LEDs for optical communication in POF (λ = 645 nm) and a silicon light sensor. The Super ESKA® plastic fibers were used to implement the fiber intensity sensor, arranged in a 4 × 4 matrix. During the breathing cycles, the force transmitted from the lungs to the thorax is in the order of tens of Newtons, and the respiration rate is of one breath every 2–5 s (0.2–0.5 Hz). The sensor has a resolution of force applied on a single point of 2.2–4.5%/N on the normalized voltage output, and a bandwidth of 10 Hz, it is then suitable to monitor the respiration movements. Another issue to be addressed is the presence of hysteresis over load cycles. The sensor was loaded cyclically to estimate the drift of the system, and the hysteresis was found to be negligible.

COMPUTERIZED RADIAL ARTERY PULSE SIGNAL CLASSIFICATION FOR LUNG CANCER DETECTION

Pulse diagnosis, the main diagnosis method in traditional Chinese medicine, is a non-invasive and convenient way to check the health status. Doctors usually use three fingers to feel three positions; Cun, Guan, and Chi of the wrist pulse, to diagnose the body’s healthy status. However, it takes many years to master the pulse diagnosis. This paper aims at finding the best position for acquiring wrist-pulse-signal for lung cancer diagnosis. In our paper, the wrist-pulse-signals of Cun, Guan, and Chi are acquired by three optic fiber pressure sensors of the same type. Twelve features are extracted from the signals of these three positions, respectively. Eight classifiers are applied to detect the effectiveness of the signal acquired from each position by classifying the pulse signals of healthy individuals and lung cancer patients. The results achieved by the proposed features show that the signal acquired at Cun is more effective for lung cancer diagnosis than the signals acquired at Guan and Chi.

MEMS optical interferometry-based pressure sensor using elastomer nanosheet developed by dry transfer technique

We developed an elastomer-based Fabry–Perot interferometer with a submicron gap between a freestanding thin film and a substrate by a dry transfer technique. A newly developed elastomeric nanosheet using a polystyrene–polybutadiene–polystyrene triblock copolymer (SBS) provides a low Young’s modulus of 40 MPa, a large elastic strain of 38%, and high adhesiveness. A freestanding SBS nanosheet can be formed by a dry transfer technique without vacuum and high-temperature processes owing to the high adhesiveness of SBS nanosheets. With the pressure change, the freestanding nanosheet was found to deform with good adhesion between the dry transferred SBS and the substrate.

Non-destructive residual pressure self-measurement method for the sensing chip of optical Fabry-Perot pressure sensor.

We introduce a simple residual pressure self-measurement method for the Fabry-Perot (F-P) cavity of optical MEMS pressure sensor. No extra installation is required and the structure of the sensor is unchanged. In the method, the relationship between residual pressure and external pressure under the same diaphragm deflection condition at different temperatures is analyzed by using the deflection formula of the circular plate with clamped edges and the ideal gas law. Based on this, the residual pressure under the flat condition can be obtained by pressure scanning process and calculation process. We carried out the experiment to compare the residual pressures of two batches MEMS sensors fabricated by two kinds of bonding process. The measurement result indicates that our approach is reliable enough for the measurement.

High pressure sensitivity of anti-Stokes fluorescence in Nd3+ doped yttrium orthoaluminate nano-perovskites

Pressure-induced energy shifts of anti-Stokes emissions of Nd3+:YAlO3 nano-perovskite has been studied up to 10GPa. Emission lines have been identified as thermally-induced transitions between 4F7/2, 4S3/2, and 4F9/2 multiplets and the 4I9/2 ground state, which emerge as a consequence of the heat produced in the sample by using a confocal set up, which condenses the energy of the laser beam in a micro-sized spot. Blue and red-shifts have been observed with linear pressure coefficients that range from +3.15cm−1/GPa to −7.21cm−1/GPa. These results suggest the use of Nd3+:YAlO3 nano-perovskite in high pressure experiments as an optical pressure sensor in the wavelength interval from 660 to 760nm.

Comparison of Resting PD/PA with Fractional Flow Reserve Using a Monorail Pressure Catheter

Background: The RXi™ system (ACIST Medical Systems, MN, USA) is a new Fractional Flow Reserve (FFR) technology utilising an ultrathinmonorail microcatheter (Navvus®; ACIST Medical Systems) with an optical pressure sensor located close to the distal catheter tip. FFR measurement using monorail microcatheter is comparable to the conventional pressure wires. However, the predictive value of resting distal coronary artery pressure/aortic pressure (Pd/Pa) on hyperemic FFR value in the real world practice is unknown. Objective: To explore the diagnostic accuracy of resting Pd/Pa in relation to hyperemic FFR using the monorail pressure catheter. Methods: Resting Pd/Pa and FFR were measured using monorail pressure catheter in 67 consecutive patients with intermediate coronary artery lesions (30% to 80% diameter stenoses) between 01-03-2016 to 17-01-2017. Of 121 studied lesions, 29 (23.97%) were excluded because of no hyperemic FFR due to postive resting Pd/Pa (n=17), severe or non-critical stenosis (n=11) and suboptimal acquisition (n=1), leaving 92 lesions for final analysis. Hyperemic FFR was induced with intracoronary adenosine. The selection of coronary wire and the dose of intracoronary nitroglycerine were at the operators’ discretions. Results: Bland-Altman plots showed a moderate degree of scatter between Pd/Pa and FFR value. On average, Pd/Pa exceeded FFR by 0.066 (-0.09 to +0.22). Receiver-operating characteristic curves of the resting Pd/Pa with FFR≤0.80 as the reference variable showed an area under the curve of 0.78 (95% confidence intervals 0.680 to 0.881, pb0.001), with a diagnostic accuracy of 79.3% when the resting Pd/Pa was ≤0.86. Certain cutoff values of Pd/Pa can reliably predict whether hyperemic FFR was positive or negative (FFR cutoff≤0.80). Resting Pd/Pa value of N0.96 had a negative predictive value (NPV) of 100% and sensitivity of 100%; the resting Pd/Pa value of ≤0.82 had a positive predictive value (PPV) of 100% and specificity of 98.3%. These were consistent regardless of coronary vessel, location of lesion or degree of diameter stenosis. Conclusions: Certain range of resting Pd/Pa measured by monorail pressure catheter had excellent NPV and sensitivity or excellent PPV and specificity to predict hyperemic FFR. Clinical outcome studies are required to determine whether the results might obviate the need for hyperemia in selected patients.

Optical Fiber Bragg Grating Pressure Sensor Based on Dual-Frequency Optoelectronic Oscillator

A dual-frequency optoelectronic oscillator (OEO) for high sensitivity pressure sensing is proposed and experimentally demonstrated. The oscillation frequency of the OEO is determined by a dual-passband microwave photonic filter in the OEO loop, which is implemented using phase shifted fiber Bragg gratings (PSFBGs) written in side-hole fiber to perform phase-modulation to intensity-modulation conversion. When the PSFBGs are experiencing a pressure, the wavelength difference between the two notches of the PSFBGs is slightly changed, which leads to a large frequency change of the two oscillating frequencies. Since the beat frequency between the two microwave signals is linearly proportional to the pressure, the high sensitivity pressure measurement can be realized through monitoring the beat frequency. The proposed approach is experimentally evaluated. High sensitivity pressure sensing with a sensitivity of 418.8 MHz/MPa is experimentally demonstrated. In addition, the sensing is insensitive to the variations of the environmental temperature.

Development of a Shipboard Remote Control and Telemetry Experimental System for Large-Scale Model's Motions and Loads Measurement in Realistic Sea Waves.

Wave-induced motion and load responses are important criteria for ship performance evaluation. Physical experiments have long been an indispensable tool in the predictions of ship’s navigation state, speed, motions, accelerations, sectional loads and wave impact pressure. Currently, majority of the experiments are conducted in laboratory tank environment, where the wave environments are different from the realistic sea waves. In this paper, a laboratory tank testing system for ship motions and loads measurement is reviewed and reported first. Then, a novel large-scale model measurement technique is developed based on the laboratory testing foundations to obtain accurate motion and load responses of ships in realistic sea conditions. For this purpose, a suite of advanced remote control and telemetry experimental system was developed in-house to allow for the implementation of large-scale model seakeeping measurement at sea. The experimental system includes a series of technique sensors, e.g., the Global Position System/Inertial Navigation System (GPS/INS) module, course top, optical fiber sensors, strain gauges, pressure sensors and accelerometers. The developed measurement system was tested by field experiments in coastal seas, which indicates that the proposed large-scale model testing scheme is capable and feasible. Meaningful data including ocean environment parameters, ship navigation state, motions and loads were obtained through the sea trial campaign.

Design and development of lab model of piezo-optic sensor for Structural Health Monitoring

This work deals with fibre optic pressure sensors for Structural Health Monitoring (SHM) based on the piezo-optic principle. Various samples were prepared and investigated under room ambient conditions. In one of the samples, periodic microbends of 1 cm spatial periodicity were introduced in the PCS600 optical fibre, which was then embedded in an Araldite matrix with the composition of 60% hardener and 40% resin. This sample was marked as S1. In another sample, the same fibre without microbending was embedded in the same Araldite matrix, and was marked as S2. In another sample, the fibre without microbending was embedded in a cement matrix composite, and was marked as S3. Sample S3 was an effort to develop a pressure sensor for real working environment. Here conventional portland cement was used for the fabrication of the sample. High pressure up to 60 KPa was applied to the sample under cyclic loading and unloading, and the corresponding output power noted. Sensitivities of fibre optic pressure sensor for samples S1, S2 and S3 are 2.304, 0.906 and 2.218 nW KPa–1, with reproducibilities 96.61%, 97.95% and 87.24% respectively. The sensitivities obtained indicate that the sensor has excellent potential to replace existing bulky electrical sensors.

A chip-integrated optical microfluidic pressure sensor

Pressure sensing inside microfluidic channels in glass chips was achieved by integrating an oxygen sensitive luminescent sensor layer inside of an air-filled cavity. The device enables reliable determination of gas pressures, as well as flow rate-induced liquid backpressures at various positions along a channel. This optically readable microfluidic pressure sensor allows on-chip pressure sensing with high sensitivity at up to 9 mbar, and unsurpassed working range from atmospheric pressure up to 5bar. Investigation of the system revealed high flexibility, stability and reproducibility of the proposed method. In addition to the pressure determination, the integrated luminescent sensor allows simultaneous detection of the temperature and oxygen content of a process medium.