Pressure Microsensor Research Articles

The simulation, fabrication technology and characteristic research of micro-pressure sensor with isosceles trapezoidal beam-membrane

A micro-pressure sensor with an isosceles trapezoidal beam-membrane (ITBM) is proposed in this paper, consisting of a square silicon membrane, four isosceles trapezoidal beams (ITBs) and four piezoresistors. To investigate how the elastic silicon membrane affects pressure sensitive characteristics, simulation models based on ANSYS 15.0 software were used to analyze the effect of structural dimension on the characteristics of pressure sensor. According to that, the chips of micro-pressure sensors were fabricated by micro-electro-mechanical system (MEMS) technology on a silicon wafer with [Formula: see text] orientation. The experimental results show that the proposed sensor achieves a better sensitivity of 9.64 mV/kPa and an excellent linearity of 0.09%F.S. in the range of 0–3.0 kPa at room temperature and a supply voltage of 5.0 V, with a super temperature coefficient of sensitivity (TCS) about - 2180 ppm/[Formula: see text] from −40[Formula: see text] to 85[Formula: see text] and low pressure measurement less than 3.0 kPa.

Understanding vibrant behavior of Si-circular diaphragm for low-pressure measurement

Enhanced sensitivity, precise measurements and accuracy are the key factors to identify the performance of any sensor. In this paper, p-polycrystalline silicon micro-pressure sensor has been designed which works on the principle of piezoresistive effect. A theoretical modeling and computational simulation of the circular Si-diaphragm have been performed through the extensive study of stress and frequency response with the help of finite element method (FEM) within the framework of COMSOL. For a thin diaphragm ([Formula: see text][Formula: see text]50 [Formula: see text]m), the Eigen frequency and the frequency generated in a diaphragm under the influence of pressure has been optimized within the pressure range from 1–25 kPa. The modes of vibrations generated in the diaphragm have been optimized at wide-frequency range [Formula: see text][Formula: see text]200–800 kHz at various pressure values. The findings of the presented research have suggested that for a [Formula: see text][Formula: see text]50 [Formula: see text]m thin diaphragm, the optimized fundamental frequency is [Formula: see text][Formula: see text]310 kHz for showing better piezoresistive response which results into enhanced sensitivity. Moreover, the simulation results show that for the designed sensor, the pressure sensitivity of [Formula: see text][Formula: see text]11.51 mv/psi has been conveyed.

A new pressure microsensor based on dual-gate graphene field-effect transistor with a vertically movable top-gate: Proposal, analysis, and optimization

The combination of modern electronic devices and nanoelectromechanical systems (NEMS) has given new impulses to the development of sensors and biosensors. A new pressure microsensor based on graphene field-effect transistor (GFET) endowed with dual-gate design is proposed herein. The movable top-gate concept is used as sensing principle to detect the pressure-induced nanoscale displacement. A compact GFET drain-current model based on drift-diffusion carrier transport and field-effect principle is employed for the performance assessment of the proposed pressure microsensor. The investigation includes the top-gate and dual-gate configuration, transfer characteristic behavior, sensitivity analysis, operating regime, and the impact of gates' biases on the microsensor sensitivity. The performance analysis reveals that the dual-gate GFET design outperforms the top-gated GFET in terms of sensitivity. In addition, the high back-gate voltage and the low drain-source voltage have been found useful in improving the sensitivity of the DG GFET-based pressure sensor. Moreover, a metaheuristic optimization technique based on genetic algorithm (GA) has been adopted to find the optimal sensor parameters values that lead to the best sensitivity performance. The merits of the proposed dual-gate GFET-based pressure microsensor, namely small-size, high-sensitivity, graphene cost, and CMOS compatibility, make it a promising candidate for high-performance pressure sensing applications.

Eccentric reflective optical fiber MEMS micro-pressure sensor

An eccentric reflective optical fiber micro-electro-mechanical system (MEMS) micro-pressure sensor is proposed in this paper. The core part of the sensor consists of a dual fiber collimator (a fiber collimator with two pigtails) in an eccentric position and a sensitive silicon diaphragm. The sensitive silicon diaphragm adopts the BM (beam-membrane) structure with small structural parameters manufactured by MEMS manufacturing technology. Simulation results show that the BM structure has good sensitivity and high natural frequency. Overall structure of the sensor with the measurement range of 0 ∼ 10 kPa is designed. The way of intensity demodulation ensures the performance and stability of the sensor and makes the sensing system easier to process signals. By building a static test platform and conducting experiments, we can conclude that the sensitivity of the sensor is −0.32 dB kPa−1. Furthermore, the repeatability of the sensor is 1.26%FS (full-scale), the hysteresis of the sensor is 0.95%FS and the zero drift of the sensor is 0.615%FS h–1. By building a dynamic experimental platform and conducting experiments, it can be seen that the response time of the sensor is 0.47 ms (<1 ms), the sensor has good dynamic response.

Rapid and Accurate Pressure Sensing Device for Direct Measurement of Intraocular Pressure.

PurposeIntraocular pressure (IOP) is the primary modifiable risk factor for glaucoma. Current devices measure IOP via the dynamic response of the healthy cornea and do not provide the accurate IOP measurements for patients with altered corneal biomechanics. We seek to develop and test an accurate needle-based IOP measurement device that is not cornea dependent.MethodsOur device combines a high-resolution pressure microsensor with 30- and 33-gauge Luer lock needles to provide IOP measurements via a microcontroller and USB interface to a computer. The device was calibrated in a membrane chamber and then tested and validated in the anterior chamber and post-vitrectomy vitreous chamber of rabbit eyes. The results were compared to Tonopen readings across a pressure range of 0 to 100 mm Hg, imposed in increments of 10 mm Hg.ResultsBoth the needle based sensor device and the Tonopen demonstrated a linear relationship with changes in imposed pressure. The Tonopen was found to consistently underestimate the IOP both in the anterior and vitreous chambers. The Tonopen exhibited a significantly greater error than our needle-based sensor device. With increased pressure (>30 mm Hg), the error of the Tonopen increased, whereas the error of our device did not. The 30-gauge needle produces an insignificant improvement in accuracy over the 33-gauge needle.ConclusionsA needle-based sensor device enables accurate IOP measurements over a broad range of induced IOP.Translational RelevanceDirect measurement of IOP in the anterior chamber circumvents the influence of corneal parameters on IOP measurement.

Fitting analysis and research of measured data of SAW micro-pressure sensor based on BP neural network

Sensor technology plays an important role in modern information and intelligence. The accuracy of sensor measurement becomes more challenging in complex working environment. In this paper, we studied relationship between output frequency difference data and corresponding loading pressure in SAW (Surface Acoustic Wave) micro-pressure sensor. Then using frequency difference as input and pressure as output, we construct BP (Back Propagation) neural network which is trained using experimental data and used to predict output pressure of the sensor. We also calculate error with actual loading pressure, same in the least squares method commonly used. Through multiple comparisons of same set of sample data in overall and local accuracy of predicted results, we verified that the output error predicted by BP neural network is much smaller than least squares method. For example, one set of data is only about 2.9%. It provided a new method for data analysis in SAW micro-pressure sensor.

A high sensitivity micro-pressure sensor based on 3D printing and screen-printing technologies

A 3D-printed micro-pressure sensor with high sensitivity is developed in this paper. It is a fully printed pressure sensor fabricated using a combination of digital light processing (DLP)-based printing and screen-printing technologies, with the advantages of high manufacturing efficiency and low cost. The pressure sensor consists of a sensor substrate with a circular diaphragm and a Wheatstone bridge on the surface. First, the pressure sensor was theoretically analyzed and then verified using the finite element method (FEM). During fabrication, the sensor substrate was made from a transparent high-temperature resin, which was printed by a DLP-based 3D printer. The resistors and leads of the Wheatstone bridge were made from carbon paste and silver paste, respectively, and printed by screen-printing technology. Then, the resistors were characterized to find the gauge factor and the print consistency between different resistors. Next, the experimental setup was established for the characterization of the pressure sensor. Three loops of pressurization and depressurization from 0 kPa to 2.4 kPa were applied to the pressure sensor continuously, and the output voltage was recorded. The experimental results show that the gauge factor of the carbon resistor is 17.01 ± 1.85, the sensitivity of the sensor is 4.5522 mV/kPa/5 V, the linearity error is 2.077% FS, the hysteresis error is 6.327% FS and the repeatability error is 5.708% FS. Also, it is very convenient to obtain pressure sensors with different sensitivities and measurement ranges by changing the thickness of the circular diaphragm. All these results prove that the proposed sensor provides a low cost and high sensitivity approach for micro-pressure measurement, and that 3D printing can be applied to the production of personalized sensors.

Increased stiffness and flow resistance of the inner wall of Schlemm’s canal in glaucomatous human eyes

The cause of the elevated outflow resistance and consequent ocular hypertension characteristic of glaucoma is unknown. To investigate possible causes for this flow resistance, we used atomic force microscopy (AFM) with 10-µm spherical tips to probe the stiffness of the inner wall of Schlemm's canal as a function of distance from the tissue surface in normal and glaucomatous postmortem human eyes, and 1-µm spherical AFM tips to probe the region immediately below the tissue surface. To localize flow resistance, perfusion and imaging methods were used to characterize the pressure drop in the immediate vicinity of the inner wall using giant vacuoles that form in Schlemm's canal cells as micropressure sensors. Tissue stiffness increased with increasing AFM indentation depth. Tissues from glaucomatous eyes were stiffer compared with normal eyes, with greatly increased stiffness residing within ∼1 µm of the inner-wall surface. Giant vacuole size and density were similar in normal and glaucomatous eyes despite lower flow rate through the latter due to their higher flow resistance. This implied that the elevated flow resistance found in the glaucomatous eyes was localized to the same region as the increased tissue stiffness. Our findings implicate pathological changes to biophysical characteristics of Schlemm's canal endothelia and/or their immediate underlying extracellular matrix as cause for ocular hypertension in glaucoma.

Wireless intravesical device for real-time bladder pressure measurement: Study of consecutive voiding in awake minipigs.

Traditional urodynamics have poor correlation with urological symptoms. Ambulatory urodynamics may improve this correlation but the need for a transurethral catheter and the time-consuming nature of this examination limits its use. Therefore, the objective of this study was to develop a wireless real-time bladder pressure measurement device for repeated and prolonged-term measurement of bladder behavior in awake pigs. The Bladder Pill is an intravesical device with a pressure microsensor and a 3-dimensional inductive coupling coil for energy supply. A corresponding external coil provides wireless power transmission and real-time communication of bladder pressure data. To test the correlation between the pressure data measured by the device and by standard methods, we compared static water column pressures with this device and water-filled urodynamic catheter systems. In vivo assessment of awake voiding by the pill was done by introducing the bladder pill into the bladder of Göttingen minipigs. An air-charged urodynamic catheter was introduced transurethrally as control for pressure measurements. The optimal physical configuration of the pill was investigated to maximize the containment in the bladder. We used two versions of external signal receivers (one waistband and one rectangular frame) to test the optimal external signal capture. Next to that, we performed short-term and medium-term comparative pressure studies. The in vitro static pressure measurement demonstrated a mean difference of less than 1 cm H2O between the methods. The optimal design of the pill for maximal retainment in the bladder proved to be a pigtail configuration. The bending of the device during bladder contractions caused offset of 2.7 +/- 1.4 cm H2O (mean +/- SD) on the pressure measurements. The rectangular frame performed signal capture during 5 consecutive voids with a good correlation of the pressure measurements. The device can be inserted through the urethra and is retrieved using string or endoscopic extraction. In conclusion, wireless long-term measurement of bladder pressure is demonstrated and yields comparable results to current available catheter methods of measurement in a pig model.

Highly sensitive and wide-range resonant pressure sensor based on the veering phenomenon

We report a highly sensitive wide-range resonant pressure sensor. The concept is based on tracking multiple modes of vibration of an electrothermally heated initially curved micro-beam experiencing the veering phenomenon between its first and third vibration modes. For low values of pressure, the third resonance frequency is very sensitive, and thus its variation with pressure is monitored and recorded. As increasing pressure, the resonance frequency of the third mode decreases until reaching the veering phenomenon. At that point, the first mode exchanges role with the third mode, becoming very sensitive, and hence its frequency is tracked afterward as varying pressure. We show that using this concept, the sensitivity of the resonant pressure micro-sensor is significantly enhanced. Finite element method (FEM) simulations and experimental data show that the proposed micro-sensor becomes highly sensitive for wide-range of pressure from 38 mTorr to 200 Torr. The effect of various parameters on the performance of the proposed pressure sensor is investigated including the thickness of the micro-beam, the vacuum chamber size, and the thermal actuation load.

A Resonant Pressure Microsensor With a Stress Isolation Layer

This paper presents a resonant pressure microsensor composed of a glass cap for hermetic package, an SOI layer with sensing elements and a glass base for stress isolation. Tested pressure under measurement bends the pressure sensitive diaphragm, producing frequency shifts of underlining resonators while the stress isolation layer can work as a cushion layer to minimize environmental temperature and mechanical disturbances. Numerical simulations were conducted, finding that the stress isolation layer can decrease the axial stresses of the resonators from +16 to +2 MPa (high-temperature challenging), from −12 to −5 MPa (low-temperature challenging), and from 2.5 to 0.5 MPa (mechanical challenging). The proposed microsensor was fabricated based on conventional microfabrication and characterized with comparison to the counterpart without the stress isolation layer, producing an accuracy of 0.01% FS vs. 1% FS, a temperature shift of 37 ppm versus 10088 ppm, a pressure shift of 45 ppm versus 777 ppm, a temperature hysteresis error of 21 ppm versus 187 ppm, a pressure hysteresis error of 22 ppm versus 265 ppm, a temperature repeatability error of 15 ppm versus 703 ppm, a pressure repeatability error of 21 ppm versus 36 ppm, and a long-term stability of >7 months versus 69 days. These results validated the functionality of the proposed resonant pressure microsensor with the stress isolation layer, which may be potentially used as an effective tool in the fields of aerospace aviation, industrial control, and meteorological monitoring.

Mathematical Modelling and Comparative Study of Elliptical and Circular Capacitive Pressure Microsensor

A lot of work on clamped circular, square and rectangular shaped capacitive pressure sensor has been carried out. However, to the best of our knowledge, no elaborate work has been performed on mathematical formulation and simulation of clamped elliptical shaped capacitive pressure sensor in literature. This paper describes the mathematical modelling and simulation of normal mode clamped elliptical shaped capacitive pressure sensor. The study of various performance parameters like maximum diaphragm deflection, capacitance variation, mechanical sensitivity, capacitive sensitivity and non-linearity is also carried out for operating pressure range of 0kPa – 18 kPa. For circular capacitive pressure sensor, the operating pressure range is modified according to physical dimensions i.e. thickness and radius of diaphragm, separation gap between plates and maximum deflection. For same overlapping area between plates (10000π mm2), the comparison of elliptical shapes of different eccentricities with circular shape diaphragm is carried out. The thickness of diaphragm is taken as2 μm and separation gap is 1 μm in all the designs which are used in this work. In this comparative study, it is observed that elliptical shaped capacitive pressure sensors have better linearity than circular diaphragm pressure sensor.

A Resonant Pressure Microsensor with the Measurement Range of 1 MPa Based on Sensitivities Balanced Dual Resonators.

This paper presents a resonant pressure microsensor with the measurement range of 1 MPa suitable for the soaring demands of industrial gas pressure calibration equipment. The proposed microsensor consists of an SOI layer as a sensing element and a glass cap for vacuum packaging. The sensing elements include a pressure-sensitive diaphragm and two resonators embedded in the diaphragm by anchor structures. The resonators are excited by a convenient Lorentz force and detected by electromagnetic induction, which can maintain high signal outputs. In operation, the pressure under measurement bends the pressure-sensitive diaphragm of the microsensor, producing frequency shifts of the two underlining resonators. The microsensor structures were designed and optimized using finite element analyses and a 4” SOI wafer was employed in fabrications, which requires only one photolithographic step. Experimental results indicate that the Q-factors of the resonators are higher than 25,000 with a differential temperature sensitivity of 0.22 Hz/°C, pressure sensitivities of 6.6 Hz/kPa, and −6.5 Hz/kPa, which match the simulation results of differential temperature sensitivity of 0.2 Hz/°C and pressure sensitivities of ±6.5 Hz/kPa. In addition, characterizations based on a closed-loop manner indicate that the presented sensor demonstrates low fitting errors within 0.01% FS, high accuracy of 0.01% FS in the pressure range of 20 kPa to 1 MPa and temperature range of −55 to 85 °C, and the long-term stability within 0.01% FS in a 156-day period under the room temperature.

Thermomechanical Study and Fracture Properties of Silicon Wafer under Effect of Crystal Orientation

Designing and optimizing the performance of a piezoresistive pressure microsensor involves not only studying the piezoresistive properties of polysilicon but also analyse the thermomechanical behaviour of its most sensitive internal part. This work focuses on an analytical, numerical and experimental study of a silicon wafer used in a pressure sensor. A thermomechanical study was conducted to assess the effects of temperature and material orientation on the deflexion and failure mode of Silicon membrane. The chosen analytical approach is based on Kirchhoff theory in which a square Silicon membrane is subjected to a distributed pressure over all its surface. Thermomechanical simulations and fracture analysis are carried out using Abaqus software. An experimental thermomechanical technique to determine maximum wafer deflexion and its effect on crack initiation and fracture mode was implemented. Deflexions tests were carried out on a bending machine using specimens of p-Si doped wafers. Deflexion values are measured for each applied temperature. Some preliminary tests were performed to determine the impact of temperature and Silicon wafers orientation on maximum deflexion when fracture occurs. The test’s results confirmed that the failure mode is highly brittle and follow each time crystal orientations 0° and 45°. Furthermore, at room temperature, fracture occur at 389 μm of displacement, and grows by 5.2 % when temperature is increased over 40°C. Consequently, Silicon sensitivity will be increased by 4%.

Numerical Investigation of Quasi-Lamb Modes in C‑Tilted ZnO/SiC Composite Membrane for High Performance Pressure Micro-Sensor

Using the finite element method, we have studied the Lamb modes characteristics propagation in c‑tilted ZnO/SiC thin film composite membrane. Phase velocity dispersion curves, electromechanical coupling factors and the mass loading effect on the fundamental quasi Lamb modes are theoretically investigated for different rotating angle (0°, θ°, 90°), θ being the angle of rotation, and for different hZnO/λ values. To develop high performance pressure micro-sensor based on thin film piezoelectric ZnO on amorphous SiC (range 0.1 to 100 Pa) the anti-symmetric fundamental qA0 mode phase shift is studied for pressure sensing.

A Flexible 5-In-1 Microsensor for Internal Microscopic Diagnosis of Vanadium Redox Flow Battery Charging Process.

Multiple important physical parameters in the vanadium redox flow battery are difficult to measure accurately, and the multiple important physical parameters (e.g., temperature, flow, voltage, current, pressure, and electrolyte concentration) are correlated with each other; all of them have a critical influence on the performance and life of vanadium redox flow battery. In terms of the feed of fuel to vanadium redox flow battery, the pump conveys electrolytes from the outside to inside for reaction. As the performance of vanadium redox flow battery can be tested only by an external machine—after which, the speed of pump is adjusted to control the flow velocity of electrolyte—the optimum performance cannot be obtained. There is a demand for internal real-time microscopic diagnosis of vanadium redox flow batteries, and this study uses micro-electro-mechanical systems (MEMS) technology to develop a flexible five-in-one (temperature, flow, voltage, current, and pressure) microsensor, which is embedded in vanadium redox flow battery, for real-time sensing. Its advantages include: (1) Small size and the simultaneous measurement of five important physical quantities; (2) elastic measurement position and accurate embedding; and (3) high accuracy, sensitivity, and quick response time. The flexible five-in-one microsensor embedded in the vanadium redox flow battery can instantly monitor the changes in different physical quantities in the vanadium redox flow battery during charging; as such, optimum operating parameters can be found out so that performance and life can be enhancec.

Evaluation of cranial base repair techniques utilizing a novel cadaveric CPAP model.

Although recent guidelines for obstructive sleep apnea recommend early postoperative use of continuous positive airway pressure (CPAP) after endonasal skull base surgery, the time of initiation of CPAP is unclear. In this study we used a novel, previously validated cadaveric model to analyze the pressures delivered to the cranial base and evaluate the effectiveness of various repair techniques to withstand positive pressure. Skull base defects were surgically created in 3 fresh human cadaver heads and repaired using 3 commonly used repair techniques: (1) Surgicel™ onlay; (2) dural substitute underlay with dural sealant onlay; and (3) dural substitute underlay with nasoseptal flap onlay with dural sealant. Pressure microsensors were placed in the sphenoid sinus and sella, both proximal and distal to the repair, respectively. The effectiveness of each repair technique against various CPAP pressure settings (5-20 cm H2 O) was analyzed. Approximately 79%-95% of positive pressure administered reached the sphenoid sinus. Sellar pressure levels varied significantly across the 3 repair techniques and were lowest after the third technique. "Breach" points (CPAP settings at which sellar repair was violated) were lowest for the first group. All 3 specimens showed a breach after the first repair technique. For the second repair technique, only a single breach was created in 1 specimen at 20 cm H2 O. No breaches were created in the third group. Different skull base repair techniques have varying ability to withstand CPAP. Both second and third repair techniques performed in a nearly similar fashion with regard to their ability to withstand positive pressure ventilation.

Analysis of measurement uncertainty of a surface acoustic wave micro-pressure sensor

As an important support for test and control projects, sensor’s performance is directly related to the accuracy of the measurement. To fully analyze the sources of measurement uncertainty for a surface acoustic wave micro-pressure sensor, in this study the Monte Carlo method and Guide to the Expression of Uncertainty in Measurement to evaluate measurement uncertainty of sensors are used, the sensing experiment was conducted and the measurement addition model was established. We determined the source of measurement uncertainty for a surface acoustic wave micro-pressure sensor. The results show that the Monte Carlo method can obtain a more reliable and accurate inclusion interval in the measurement uncertainty evaluation of a surface acoustic wave micro-pressure sensor.

A liquid metal based capacitive soft pressure microsensor.

A liquid-metal based capacitive soft pressure microsensor is proposed in this work for measuring pressure in microchannels. To measure the pressure of the target microchannel, a short detection channel is fabricated and connected to the target microchannel. Because the detection channel has only one outlet at the end which is connected to the target microchannel, the fluid in the detection channel will stay still during the measurement and the pressure remains constant inside the detection channel. A segment of reference fluid which is immiscible with the working fluid is sealed inside the detection channel. Because the chip material is soft, the pressure change will lead to the movement of the interface between the reference fluid and working fluid inside the detection channel. A pair of liquid metal electrodes are fabricated on both sides of the detection channel. By measuring the capacitance between these two liquid metal electrodes, the movement of the interface can be detected, and thus the pressure change can be detected as well. To minimize the influence from the environment, two liquid metal shield layers are placed on the top and the bottom of the microchannel layer separately. The microsensor was first tested in a microfluidic system and then utilized to measure the blood pressure of rabbit carotid artery in vivo. The experimental results showed excellent stability and linear correlation between capacitance and the value of fluid pressure. The pressure sensor can achieve a resolution of 7.5 mmHg within a pressure range of 20-300 mmHg. This work provides a promising approach to develop an implantable blood or intraocular pressure-monitoring device for clinical use.

A salivary sensor for the management of xerostomia in edentulous patients

This article describes a method for managing xerostomia in edentulous patients with a newly developed salivary sensor. A micropressure sensor unit with a capsule to hold artificial salivary substitute was built into the dental prosthesis. This sensor prosthesis can help patients overcome mouth dryness, improves patient comfort, and aids in retention of the prosthesis.