High-sensitivity Pressure Sensor Research Articles

Simulation of capacitive pressure sensor based on microelectromechanical systems technology

This paper proposes a very high sensitivity pressure sensor with a novel technique for temperature compensation. The proposed technique employs a geometrical method for self-compensation of Young’s modulus reduction due to temperature increase, where a stronger spring with much larger length and width is anchored. According to the connection of the suspension spring to the larger spring, in higher temperatures, the large spring experiences more length increase, which in turn increases the stiffness of the suspension spring and, consequently, could compensates the Young’s modulus reduction. Simulation results verify that the temperature variation related error in the compensated sensor is less than 0.66% of full-scale under 260 ℃ of temperature range, which shows considerable improvement in comparison with literature. The total consumed area is about 0.033 mm2 with the sensitivity of 290 × 10−6 K−1.

Capacitive pressure sensing with suspended graphene-polymer heterostructure membranes.

We describe the fabrication and characterisation of a capacitive pressure sensor formed by an ultra-thin graphene-polymer heterostructure membrane spanning a large array of micro-cavities each up to 30 μm in diameter with 100% yield. Sensors covering an area of just 1 mm2 show reproducible pressure transduction under static and dynamic loading up to pressures of 250 kPa. The measured capacitance change in response to pressure is in good agreement with calculations. Further, we demonstrate high-sensitivity pressure sensors by applying a novel strained membrane transfer and optimising the sensor architecture. This method enables suspended structures with less than 50 nm of air dielectric gap, giving a pressure sensitivity of 123 aF Pa-1 mm-2 over a pressure range of 0 to 100 kPa.

A Flexible and Highly Sensitive Pressure Sensor Based on a PDMS Foam Coated with Graphene Nanoplatelets.

The demand for high performance multifunctional wearable devices is more and more pushing towards the development of novel low-cost, soft and flexible sensors with high sensitivity. In the present work, we describe the fabrication process and the properties of new polydimethylsiloxane (PDMS) foams loaded with multilayer graphene nanoplatelets (MLGs) for application as high sensitive piezoresistive pressure sensors. The effective DC conductivity of the produced foams is measured as a function of MLG loading. The piezoresistive response of the MLG-PDMS foam-based sensor at different strain rates is assessed through quasi-static pressure tests. The results of the experimental investigations demonstrated that sensor loaded with 0.96 wt.% of MLGs is characterized by a highly repeatable pressure-dependent conductance after a few stabilization cycles and it is suitable for detecting compressive stresses as low as 10 kPa, with a sensitivity of 0.23 kPa−1, corresponding to an applied pressure of 70 kPa. Moreover, it is estimated that the sensor is able to detect pressure variations of ~1 Pa. Therefore, the new graphene-PDMS composite foam is a lightweight cost-effective material, suitable for sensing applications in the subtle or low and medium pressure ranges.

Numerical and experimental studies of high-sensitivity plug-in pressure sensor based on fiber Bragg gratings

A high-sensitivity pressure sensor based on wavelength detection technology of fiber Bragg grating (FBG) is proposed in this paper. The FBG pressure sensor can be used to measure downhole pressure of oil and gas wells. An eccentric-pushrod structure is used to improve the sensitivity of the sensor. The effect of adhesive on elastic hysteresis of the sensor is analyzed, and the adhesive with large shear modulus is used to reduce the hysteresis of the sensor. Numerical and experimental results show that this sensor possesses good linearity and repeatability, as well as little elastic hysteresis. The sensitivity of the sensor can reach 230.9 pm/MPa when the measured pressure is in the range of 0 to 20 MPa.

Polysilicon Thin Film Developed on Flexible Polyimide for Biomedical Applications

Flexible pressure and thermal sensors are the critical parts of the functional electronic skin of prostheses and robots, as well as flexible catheter/devices for multimodal biomedical monitoring. In this paper, a polysilicon thin film was developed on a flexible polyimide substrate using aluminum induced crystallization process for biomedical pressure and temperature sensing applications. The formation of polycrystalline structure was verified from the developed polysilicon film. Long term stability and real-time temperature tests were performed to evaluate potential application to the in vivo monitoring of brain or body temperature. The linear real-time change of polysilicon resistance with temperature was attained with the temperature coefficient of the resistance of −0.0027/°C and the resolution of 0.05 °C. With a gauge factor of 10.3, the polysilicon film developed in this paper represents a promising material for the development of high-sensitivity pressure sensors on flexible polyimide substrates. [2015-0106]

A high sensitive pressure sensor with the novel bossed diaphragm combined with peninsula-island structure

A Micro Electromechanical Systems (MEMS) piezoresistive pressure sensor chip with high sensitivity has been developed to measure the ultra-low pressure of several mbar. A novel bossed diaphragm combined with peninsula-island structure is designed. The proposed diaphragm can alleviate the trade-off between sensitivity and non-linearity to realize the measurement of ultra-low pressure with low non-linearity. Especially, the strain energy dissipating outside the stress concentration region (SCR) is reduced remarkably by the proposed diaphragm to achieve high sensitivity. The optimization process for the proposed diaphragm has been presented by finite element method (FEM) to make the sensor chip achieve a higher sensitivity and a lower non-linearity. A fabricated pressure sensor was packaged with the proposed sensor chip and tested to obtain the sensitivity of 0.066mV/V/Pa and non-linearity of 0.33%FS in the working range of 0–500Pa. The proposed sensor chip is potentially a better choice for high sensitive pressure sensor.

A high sensitivity pressure sensor based on two-dimensional photonic crystal

In this paper, we propose and simulate a pressure sensor based on two-dimensional photonic crystal with the high quality factor and sensitivity. The sensor is formed by the coupling of two photonic crystal based waveguides and one nanocavity. The photonic crystal with the triangular lattice is composed of GaAs rods. The detailed structures of the waveguides and nanocavity are optimized to achieve better quality factor and sensitivity of the sensor. For the optimized structures, the resonant wavelength of the sensor has a linear redshift as increasing the applied pressure in the range of 0–2 GPa, and the quality factor keeps unchanged nearly. The optimized quality factor is around 1500, and the sensitivity is up to 13.9 nm/GPa.

Design of High Sensitivity and Linearity Microelectromechanical Systems Capacitive Tire Pressure Sensor using Stepped Membrane

This paper is focused on a novel design of stepped diaphragm for MEMS capacitive pressure sensor used in tire pressure monitoring system. The structure of sensor diaphragm plays a key role for determining the sensitivity of the sensor and the non-linearity of the output.First the structures of two capacitive pressure sensors with clamped square flatdiaphragms, with different thicknesses are investigatedand their sensitivity and non-linearityare compared together.Finally for increasing the sensitivity and linearity,anew capacitive pressure sensor with a stepped diaphragm is introduced. A numerical solution for determination of theaccurate sensitivity of the sensor is presented.The results show that the sensitivity of the sensor is increased from 0.063 fF/KPa with flat diaphragm to 0.107 fF/KPa with stepped diaphragm and also the non-linearity is decreased from 2.37% to 1.857%. In this design, the sensor sensitivity and output linearity are increased simultaneously.

A novel technique towards deployment of hydrostatic pressure based level sensor in nuclear fuel reprocessing facility.

A novel approach towards deployment of a hydrostatic pressure based level monitoring device is presented for continuous monitoring of liquid level in a reservoir with high resolution and precision. Some of the major drawbacks such as spurious information of measured level due to change in ambient temperature, requirement of high resolution pressure sensor, and bubbling effect by passing air or any gaseous fluid into the liquid are overcome by using such a newly designed hydrostatic pressure based level monitoring device. The technique involves precise measurement of hydrostatic pressure exerted by the process liquid using a high sensitive pulsating-type differential pressure sensor (capacitive type differential pressure sensor using a specially designed oil manometer) and correlating it to the liquid level. In order to avoid strong influence of temperature on liquid level, a temperature compensation methodology is derived and used in the system. A wireless data acquisition feature has also been provided in the level monitoring device in order to work in a remote area such as a radioactive environment. At the outset, a prototype level measurement system for a 1 m tank is constructed and its test performance has been well studied. The precision, accuracy, resolution, uncertainty, sensitivity, and response time of the prototype level measurement system are found to be less than 1.1 mm in the entire range, 1%, 3 mm, <1%, 10 Hz/mm, and ∼4 s, respectively.

Structural Solution to Enhance the Sensitivity of a Self-Powered Pressure Sensor for an Artificial Tactile System.

Structural design factors of sensor units have been studied in order to enhance the sensitivity of pressure sensors based on utilizing a piezoelectric material for an artificial tactile sensor. In this study, we have primarily demonstrated the effect of a square pattern array design in a pressure sensor using ZnO nanowires. Nanowires grown on the edge of cells can be bent easily because of growth direction, density control, and buckling effect. Since smaller square pattern arrays induce a higher circumference to cell area ratio, if one sensor unit consists of many micro-level square pattern arrays, the design enhances the piezoelectric efficiency and the sensitivity. As a result, 20 μ m×20 μ m cell arrays showed three times higher pressure sensitivity than 250 μ m×250 μ m cell array structures at a pressure range from 4 kPa to 14 kPa. The induced piezoelectric voltage with the same pressure level also increased drastically. Therefore, the square pattern array design is more appropriate for a high-sensitive pressure sensor than a simple one-body cell design for tactile systems, and it has the advantage of better power efficiency, which is also important for artificial tactile systems. This suggested cell array design can be applied to various systems using piezoelectric nanowires.

Design, fabrication and characterization of a high-sensitivity pressure sensor based on nano-polysilicon thin film transistors

Based on the nano-polysilicon thin film transistors (TFTs), a high-sensitivity pressure sensor was designed and fabricated in this paper. The pressure sensing element is composed of a Wheatstone bridge with four nano-polysilicon TFTs designed on different positions of the square silicon diaphragm. Via taking the four channel resistors of the TFTs as piezoresistors, the measurement to the external pressure can be realized according to the piezoresistive effects of channel layer. Through adopting complementary metal oxide semiconductor (CMOS) technology and micro-electromechanical system (MEMS) technology, the chips of sensor were fabricated on &amp;lt;100 &amp;gt; orientation silicon wafer with a high resistivity. At room temperature, when applying a voltage 5.0 V to the Wheatstone bridge, the full scale (100 kPa) output voltage and the sensitivity of the sensor with 35 μm-thick silicon diaphragm are 267 mV and 2.58 mV/kPa, respectively. The experimental results show that the pressure sensors can achieve a much higher sensitivity.

Theoretical Design of a High Sensitivity SPR-Based Optical Fiber Pressure Sensor

A theoretical analysis for a new high-sensitivity pressure sensor based on the surface plasmon resonance (SPR) phenomenon is presented. The device consists a thin metal film deposited on the cladding of a U-shaped optical fiber probe embedded in a silicon rubber block. When the block is under pressure, the bending radius will vary and consequently a shift on the SPR wavelength can be noticed and converted to pressure units. Theoretical simulations using the transfer matrix formalism and the N-layer U-shaped fiber model were developed and implemented for three different metals: gold, copper, and silver. A resolution of 5.9 × 10−4, 6.3 × 10 −4, and 1.3 × 10−3 kPa can be expected for gold, copper, and silver, respectively for a working range up to 0.12 MPa. The proposed structure reveals to be suitable to high-sensitivity pressure measurements, including industrial operating machinery and R&D applications.

FBG based high sensitive pressure sensor and its low-cost interrogation system with enhanced resolution

A fiber Bragg grating (FBG) pressure sensor with high sensitivity and resolution has been designed and demonstrated. The sensor is configured by firmly fixing the FBG with a metal bellows structure. The sensor works by means of measuring the Bragg wavelength shift of the FBG with respect to pressure change. From the experimental results, the pressure sensitivity of the sensor is found to be 90.6 pm/psi, which is approximately 4000 times as that of a bare fiber Bragg grating. A very good linearity of 99.86% is observed between the Bragg wavelength of the FBG and applied pressure. The designed sensor shows good repeatability with a negligible hysteresis error of ± 0.29 psi. A low-cost interrogation system that includes a long period grating (LPG) and a photodiode (PD) accompanied with simple electronic circuitry is demonstrated for the FBG sensor, which enables the sensor to attain high resolution of up to 0.025 psi. Thermal-strain cross sensitivity of the FBG pressure sensor is compensated using a reference FBG temperature sensor. The designed sensor can be used for liquid level, specific gravity, and static/dynamic low pressure measurement applications.

Interference characteristics analysis of optical fiber Fabry-Perot cavity with graphene diaphragm

With regard to the design of optical fiber Fabry-Perot cavity using graphene as sensitive diaphragm,the deflection change under uniformly distributed loads in graphene film was analyzed by finite element method based on the large deflection elastic theory of circular film. The pressure-sensing mathematical model of optical fiber Fabry-Perot cavity with graphene diaphragm was established based on the working principle of Fabry-Perot interferometer. The effects of graphene film layer and incident light angle on the film reflectivity were obtained according to the refractive index characteristics of the film. Then the interference spectra change,caused by both the cavity length losses and the film deflection deformations under the pressure loads,were analyzed. The simulation results show that adding the film layer can increase the film reflectivity and further improve the optical interference performance; however,a decreasing effect on the deflection deformation is caused by the film layer with the increase of pressure load. Thus,an 8 layer graphene film can achieve a reflectivity of 0. 715% and an approximate theoretical sensitivity of 10 nm / k Pa for a 40 μm Fabry-Perot cavity length with a membrane diameter of 25 μm. It provides a theoretical basis for the design and fabrication of high-sensitivity fiber-tip pressure sensor with multiple-layer graphene diaphragm.

Structured diaphragm with a centre boss and four peninsulas for high sensitivity and high linearity pressure sensors

Using the structured diaphragm with a centre boss and four peninsulas (CBP structure), a high sensitivity and high linearity pressure sensor for low pressure ranges was demonstrated. The finite element analysis indicated that the CBP structure could achieve a far better performance than other typical structures for low pressure applications. In accordance with the simulation, the fabricated pressure sensor showed a sensitivity of 21.0 mV/V full-scale output and a nonlinearity error of 0.15% full-scale span in the pressure range of 0–5 kPa. The sensors with the CBP structure are potentially a better choice for measuring low pressures.

A high sensitivity and high linearity pressure sensor based on a peninsula-structured diaphragm for low-pressure ranges

The trade-off between sensitivity and linearity has been the major problem in designing the piezoresistive pressure sensors for low pressure ranges. To resolve the problem, a novel peninsula-structured diaphragm with specially designed piezoresistors was proposed. Finite element method (FEM) was adopted for analyzing the sensor performance as well as comparisons with other sensor structures. In comparison to flat diaphragm, the proposed sensor design could achieve a sensitivity increase by 11.4%, nonlinearity reduction of 60% and resonance frequency increase of 41.8%. In addition, the modified peninsula-structured diaphragms featuring a center boss have been optimized to achieve ultra-low nonlinearities of 0.018%FFS and 0.07%FFS for the 5kPa and 3kPa pressure ranges respectively with higher sensitivities as compared to the CBM (cross beam membrane) and hollow stiffening structures. In accordance with the FEM results, the fabricated pressure sensor with the peninsula-structured diaphragm showed a sensitivity of 18.4mV/V full-scale output and a nonlinearity error of 0.36%FSS in the pressure range 0–5kPa. The proposed sensor structure is potentially a better choice for designing low pressure sensors.

Study of a novel pressure sensor based on optical microring resonator

We propose a novel pressure sensor based on the combination of the ring resonator with two straight waveguides and a two-end fixed beam. The principle of this device is acquiring the system static pressure by monitoring the changes in the transmission wavelength shift of the ring resonator with double waveguides. The numerical results show that the sensitivity of the system is up to 49.3 pm/kPa while the pressure range is 0-300 kPa. The thickness of the fixed beam is an important factor which impacts the sensitivity of the system. This device can provide support for fabricating high sensitivity and low cost micro pressure sensors.

A high sensitive FBG pressure sensor using thin metal diaphragm

A high sensitive pressure sensor using fiber Bragg grating (FBG), integrated with thin metal diaphragm is designed and investigated both theoretically and experimentally. Under pressure the diaphragm deflection causes an axially stretched-strain along the length of the FBG. The pressure sensitivity of the sensor gained from the test results is 2.05 × 10−2 MPa−1, approximately four orders of magnitude higher than that can be measured with the bare FBG. Experimental results showed good agreement with the proposed theoretical results.

High Sensitive and Linear Pressure Sensor for Ultra-low Pressure Measurement

A novel peninsula-structured diaphragm with specially designed piezoresistors was proposed in our present pressure sensor for ultra-low pressure measurement. Finite element method (FEM) was adopted for analyzing the sensor performance. In comparison to typical sensors with flat and center-bossed diaphragms, the optimized sensor design could achieve excellent sensitivity and linearity. In accordance with the FEM results, the fabricated pressure sensor showed a sensitivity of 18.4 mV/V full-scale output and a nonlinearity error of 0.36%FSS in the pressure range 0-5 kPa. The proposed sensor structure is potentially a better choice for measuring low pressures.

Nanomechanics and vibration analysis of graphene sheets via a 2D plate model

This paper is concerned with nanomechanics and vibration analysis of graphene sheets modelled by a two-dimensional (2D) plate model in COMSOL Multiphysics. In this model, a graphene sheet is regarded as a 2D material and its thickness is changeable. Using the model, the deflection and strain or stress of graphene sheets under surface pressure or point load as well as its vibration analysis are simulated. Furthermore, the influence of different sizes, shapes and boundary conditions on the nanomechanics and vibration of graphene sheets is researched. Compared with some famous experiments and corresponding theoretical models, the simulation results show that the 2D plate model is accurate, efficient and offers a promising way of modelling nanomechanics and vibration analysis of graphene sheets. Moreover, the nonlinearity of deflection and large amplitude vibration of graphene sheets can be concluded. The deflection and fundamental frequency of graphene sheets are large enough for them to be possibly applied for high-sensitivity pressure sensors and resonators.