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Pressure, being one of the key variables investigated in scientific and engineering research, requires critical and accurate measurement techniques. With the advancements in materials and machining technologies, there is a large leap in the measurement techniques including the development of micro electromechanical systems (MEMS) sensors. These sensors are one to two orders smaller in magnitude than traditional sensors and combine electrical and mechanical components that are fabricated using integrated circuit batch-processing technologies. MEMS are finding enormous applications in many industrial fields ranging from medical to automotive, communication to electronics, chemical to aviation and many more with a potential market of billions of dollars. MEMS pressure sensors are now widely used devices owing to their intrinsic properties of small size, light weight, low cost, ease of batch fabrication and integration with an electronic circuit. This paper aims to identify and analyze the common pressure sensing techniques and discuss their uses and advantages. As per our understanding, usage of MEMS pressure sensors in the aerospace industry is quite limited due to cost constraints and indirect measurement approaches owing to the inability to locate sensors in harsh environments. The purpose of this study is to summarize the published literature for application of MEMS pressure sensors in the said field. Five broad application areas have been investigated including: propulsion/turbomachinery applications, turbulent flow diagnosis, experimentalaerodynamics, micro-flow control and unmanned aerial vehicle (UAV)/micro aerial vehicle (MAV) applications.

The first part of the paper deals with an introduction to MEMS pressure sensors and mathematical relations for its fabrication. The second part covers pressure sensing principles followed by the application of MEMS pressure sensors in five major fields of aerospace industry.

In this paper, various pressure sensing principles in MEMS and applications of MEMS technology in the aerospace industry have been reviewed. Five application fields have been investigated including: Propulsion/Turbomachinery applications, turbulent flow diagnosis, experimental aerodynamics, micro-flow control and UAV/MAV applications. Applications of MEMS sensors in the aerospace industry are quite limited due to requirements of very high accuracy, high reliability and harsh environment survivability. However, the potential for growth of this technology is foreseen due to inherent features of MEMS sensors’ being light weight, low cost, ease of batch fabrication and capability of integration with electric circuits. All these advantages are very relevant to the aerospace industry. This work is an endeavor to present a comprehensive review of such MEMS pressure sensors, which are used in the aerospace industry and have been reported in recent literature.

As per the author’s understanding, usage of MEMS pressure sensors in the aerospace industry is quite limited due to cost constraints and indirect measurement approaches owing to the inability to locate sensors in harsh environments. Present work is a prime effort in summarizing the published literature for application of MEMS pressure sensors in the said field. Five broad application areas have been investigated including: propulsion/turbomachinery applications, turbulent flow diagnosis, experimental aerodynamics, micro-flow control and UAV/MAV applications.

The present paper aims to propose a basic current mirror-sensing circuit as an alternative to the traditional Wheatstone bridge circuit for the design and development of high-sensitivity complementary metal oxide semiconductor (CMOS)–microelectromechanical systems (MEMS)-integrated pressure sensors.

This paper investigates a novel current mirror-sensing-based CMOS–MEMS-integrated pressure-sensing structure based on the piezoresistive effect in metal oxide field effect transistor (MOSFET). A resistive loaded n-channel MOSFET-based current mirror pressure-sensing circuitry has been designed using 5-μm CMOS technology. The pressure-sensing structure consists of three identical 10-μm-long and 50-μm-wide n-channel MOSFETs connected in current mirror configuration, with its input transistor as a reference MOSFET and output transistors are the pressure-sensing MOSFETs embedded at the centre and near the fixed edge of a silicon diaphragm measuring 100 × 100 × 2.5 μm. This arrangement of MOSFETs enables the sensor to sense tensile and compressive stresses, developed in the diaphragm under externally applied pressure, with respect to the input reference transistor of the mirror circuit. An analytical model describing the complete behaviour of the integrated pressure sensor has been described. The simulation results of the pressure sensor show high pressure sensitivity and a good agreement with the theoretical model has been observed. A five mask level process flow for the fabrication of the current mirror-sensing-based pressure sensor has also been described. An n-channel MOSFET with aluminium gate was fabricated to verify the fabrication process and obtain its electrical characteristics using process and device simulation software. In addition, an aluminium gate metal-oxide semiconductor (MOS) capacitor was fabricated on a two-inch p-type silicon wafer and its CV characteristic curve was also measured experimentally. Finally, the paper presents a comparative study between the current mirror pressure-sensing circuit with the traditional Wheatstone bridge.

The simulated sensitivities of the pressure-sensing MOSFETs of the current mirror-integrated pressure sensor have been found to be approximately 375 and 410 mV/MPa with respect to the reference transistor, and approximately 785 mV/MPa with respect to each other. The highest pressure sensitivities of a quarter, half and full Wheatstone bridge circuits were found to be approximately 183, 366 and 738 mV/MPa, respectively. These results clearly show that the current mirror pressure-sensing circuit is comparable and better than the traditional Wheatstone bridge circuits.

The concept of using a basic current mirror circuit for sensing tensile and compressive stresses developed in micro-mechanical structures is new, fully compatible to standard CMOS processes and has a promising application in the development of miniaturized integrated micro-sensors and sensor arrays for automobile, medical and industrial applications.

Considering its vast utility in industries, this paper aims to present a detailed review on fundamentals, classification and progresses in pressure sensors, along with its wide area of applications, its design aspects and challenges, to provide state-of-the-art gist to the researchers of the similar domain at one place.

Swiftly emerging research prospects in the micro-electro-mechanical system (MEMS) enable to build complex and sophisticated micro-structures on a substrate containing moving masses, cantilevers, flexures, levers, linkages, dampers, gears, detectors, actuators and many more on a single chip. One of the MEMS initial products that emerged into the micro-system technology is MEMS pressure sensor. Because of their high performance, low cost and compact in size, these sensors are extensively being adopted in numerous applications, namely, aerospace, automobile and bio-medical domain, etc. These application requirements drive and impose tremendous conditions on sensor design to overcome the tedious design and fabrication procedure before its reality. MEMS-based pressure sensors enable a wide range of pressure measurement as per the application requirements.

The paper provides a detailed review on fundamentals, classification and progresses in pressure sensors, along with its wide area of applications, its design aspects and challenges, to provide state of the art gist to the researchers of the similar domain at one place.

The present paper discusses the basics of MEMS pressure sensors, their working principles, different design aspects, classification, type of sensing diaphragm used and illustration of various transduction mechanisms. Moreover, this paper presents a comprehensive review on present trend of research on MEMS-based pressure sensors, its applications and the research gap observed till date along with the scope for future work, which has not been discussed in earlier reviews.

This paper aims to review the shape sensing techniques using large area flexible electronics (LAFE). Shape perception of humanoid robots using tactile data is mainly focused.

Research papers on different shape sensing methodologies of objects with large area, published in the past 15 years, are reviewed with emphasis on contact-based shape sensors. Fiber optics based shape sensing methodology is discussed for comparison purpose.

LAFE-based shape sensors of humanoid robots incorporating advanced computational data handling techniques such as neural networks and machine learning (ML) algorithms are observed to give results with best resolution in 3D shape reconstruction.

The literature review is limited to shape sensing application either two- or three-dimensional (3D) LAFE. Optical shape sensing is briefly discussed which is widely used for small area. Optical scanners provide the best 3D shape reconstruction in the noncontact-based shape sensing; here this paper focuses only on contact-based shape sensing.

Contact-based shape sensing using polymer nanocomposites is a very economical solution as compared to optical 3D scanners. Although optical 3D scanners can provide a high resolution and fast scan of the 3D shape of the object, they require line of sight and complex image reconstruction algorithms. Using LAFE larger objects can be scanned with ML and basic electronic circuitory, which reduces the price hugely.

LAFE can be used as a wearable sensor to monitor critical biological parameters. They can be used to detect shape of large body parts and aid in designing prosthetic devices. Tactile sensing in humanoid robots is accomplished by electronic skin of the robot which is a prime example of human–machine interface at workplace.

This paper reviews a unique feature of LAFE in shape sensing of large area objects. It provides insights from mechanical, electrical, hardware and software perspective in the sensor design. The most suitable approach for large object shape sensing using LAFE is also suggested.

Structures play a very important role in developing pressure sensors with good sensitivity and linearity, as they undergo deformation to the input pressure and function as the primary sensing element of the sensor. To achieve high sensitivity, thinner diaphragms are required; however, excessively thin diaphragms may induce large deflection and instability, leading to the unfavorable performances of a sensor in terms of linearity and repeatability. Thereby, importance is given to the development of innovative structures that offer good linearity and sensitivity. This paper aims to investigate the sensitivity of a bossed diaphragm coupled fixed guided beam three-dimensional (3D) structure for pressure sensor applications.

The proposed sensor comprises of mainly two sensing elements: the first being the 3D mechanical structure made of bulk silicon consisting of boss square diaphragm along with a fixed guided beam landing on to its center, forming the primary sensing element, and the diffused piezoresistors, which form the secondary sensing element, are embedded in the tensile and compression regions of the fixed guided beam. This micro mechanical 3 D structure is packaged for applying input pressure to the bottom of boss diaphragm. The sensor without pressure load has no deflection of the diaphragm; hence, no strain is observed on the fixed guided beam and also there is no change in the output voltage. When an input pressure P is applied through the pressure port, there is a deformation in the diaphragm causing a deflection, which displaces the mass and the fixed guided beam vertically, causing strain on the fixed guided beam, with tensile strain toward the guided end and compressive strain toward the fixed end of the close magnitudes. The geometrical dimensions of the structure, such as the diaphragm, boss and fixed guided beam, are optimized for linearity and maximum strain for an applied input pressure range of 0 to 10 bar. The structure is also analyzed analytically, numerically and experimentally, and the results are compared.

The structure offers equal magnitudes of tensile and compressive stresses on the surface of the fixed guided beam. It also offers good linearity and sensitivity. The analytical, simulation and experimental studies of this sensor are introduced and the results correlate with each other. Customized process steps are followed wherein two silicon-on-insulator (SOI) wafers are fusion bonded together, with SOI-1 wafer used to realize the diaphragm along with the boss and SOI-2 wafer to realize the fixed guided beam, leading to formation of a 3D structure. The geometrical dimensions of the structure, such as the diaphragm, boss and fixed guided beam, are optimized for linearity and maximum strain for an applied input pressure range of 0 to10 bar.

This paper presents a unique and compact 3D micro-mechanical structure pressure sensor with a rigid center square diaphragm (boss diaphragm) and a fixed guided beam landing at its center, with diffused piezoresistors embedded in the tensile and compression regions of the fixed guided beam. A total of six masks were involved to realize and fabricate the 3D structure and the sensor, which is presumed to be the first of its kind in the fabrication of MEMS-based piezoresistive pressure sensor.

This paper aims to describe the fabrication and characterization of current mirror-integrated microelectromechanical systems (MEMS)-based pressure sensor.

The integrated pressure-sensing structure consists of three identical 100-µm long and 500-µm wide n-channel MOSFETs connected in a resistive loaded current mirror configuration. The input transistor of the mirror acts as a constant current source MOSFET and the output transistors are the stress sensing MOSFETs embedded near the fixed edge and at the center of a square silicon diaphragm to sense tensile and compressive stresses, respectively, developed under applied pressure. The current mirror circuit was fabricated using standard polysilicon gate complementary metal oxide semiconductor (CMOS) technology on the front side of the silicon wafer and the flexible pressure sensing square silicon diaphragm, with a length of 1,050 µm and width of 88 µm, was formed by bulk micromachining process using tetramethylammonium hydroxide solution on the backside of the wafer. The pressure is monitored by the acquisition of drain voltages of the pressure sensing MOSFETs placed near the fixed edge and at the center of the diaphragm.

The current mirror-integrated pressure sensor was successfully fabricated and tested using in-house developed pressure measurement system. The pressure sensitivity of the tested sensor was found to be approximately 0.3 mV/psi (or 44.6 mV/MPa) for pressure range of 0 to 100 psi. In addition, the pressure sensor was also simulated using Intellisuite MEMS Software and simulated pressure sensitivity of the sensor was found to be approximately 53.6 mV/MPa. The simulated and measured pressure sensitivities of the pressure sensor are in close agreement.

The work reported in this paper validates the use of MOSFETs connected in current mirror configuration for the measurement of tensile and compressive stresses developed in a silicon diaphragm under applied pressure. This current mirror readout circuitry integrated with MEMS pressure-sensing structure is new and fully compatible to standard CMOS processes and has a promising application in the development CMOS-MEMS-integrated smart sensors.

This paper aims to describe the fabrication, packaging and testing of a resistive loaded p-channel metal-oxide-semiconductor field-effect transistor-based (MOSFET-based) current mirror-integrated pressure transducer.

Using the concept of piezoresistive effect in a MOSFET, three identical p-channel MOSFETs connected in current mirror configuration have been designed and fabricated using the standard polysilicon gate process and microelectromechanical system (MEMS) techniques for pressure sensing application. The channel length and width of the p-channel MOSFETs are 100 µm and 500 µm, respectively. The MOSFET M1 of the current mirror is the reference transistor that acts as the constant current source. MOSFETs M2 and M3 are the pressure-sensing transistors embedded on the diaphragm near the mid of fixed edge and at the center of the square diaphragm, respectively, to experience both the tensile and compressive stress developed due to externally applied input pressure. A flexible square diaphragm having a length of approximately 1,000 µm and thickness of 50 µm has been realized using deep-reactive ion etching of silicon on the backside of the wafer. Then, the fabricated sensor chip has been diced and mounted on a TO8 header for the testing with pressure.

The experimental result of the pressure sensor chip shows a sensitivity of approximately 0.2162 mV/psi (31.35 mV/MPa) for an input pressure of 0-100 psi. The output response shows a good linearity and very low-pressure hysteresis. In addition, the pressure-sensing structure has been simulated using the parameters of the fabricated pressure sensor and from the simulation result a pressure sensitivity of approximately 0.2283 mV/psi (33.11 mV/MPa) has been observed for input pressure ranging from 0 to 100 psi with a step size of 10 psi. The simulated and experimentally tested pressure sensitivities of the pressure sensor are in close agreement with each other.

This current mirror readout circuit-based MEMS pressure sensor is new and fully compatible to standard CMOS processes and has a promising application in the development CMOS-MEMS-integrated smart sensors.

Telemetry capsules have existed since the 1950s and were used to measure temperature, pH or pressure inside the gastrointestinal (GI) tract. It was hoped that these capsules would replace invasive techniques in the diagnosis of function disorders in the GI tract. However, problems such as signal loss and uncertainty of the pills position limited their use in a clinical setting. In this paper, a review of the capabilities of microelectromechanical systems (MEMS) for the fabrication of a wireless pressure sensor microsystem is presented.

The circuit requirements and methods of data transfer are examined. The available fabrication methods for MEMS sensors are also discussed and examples of wireless sensors are given. Finally, the drawbacks of using this technology are examined.

MEMS for use in wireless monitoring of pressure in the GI tract have been investigated. It has been shown that capacitive pressure sensors are particularly suitable for this purpose. Sensors fabricated for wireless continuous monitoring of pressure have been reviewed. Great progress, especially using surface micromachining, has been made in recent years. However, despite these advances, some challenges remain.

Provides a review of the capabilities of MEMS.

This paper aims to provide details of recently reported work on the use of nanomaterials in sensors for physical variables.

Following a short introduction, this paper first discusses research involving the use of a range of nanomaterials for strain sensing. It then considers the applications of these materials to sensors for pressure, force, touch and allied variables. It concludes with a brief discussion and 33 references.

This paper shows that nanomaterials such as carbon nanotubes, graphene, metallic nanoparticles and nanowires are being studied extensively in the physical-sensing context. All manner of sensors have been developed, based on a diversity of principles and technologies, and many offer excellent performance and unique capabilities, making them particularly well-suited to emerging applications such as wearable sensing devices.

This paper provides a detailed and timely review of the rapidly growing body of research into the use of nanomaterials for sensing physical quantities.

Detecting O₂ gas in a confined space at room temperature is particularly important to monitor the work process of precision equipment. This study aims to propose a miniaturized, low-cost, mass-scale produced O₂ sensor operating around 30°C.

The O₂ sensor based on lanthanum fluoride (LaF₃) solid electrolyte thin film was developed using MEMS technology. The principle of the sensor was a galvanic cell H₂O, O₂, Pt | LaF₃ | Sn, SnF₂ |, in which the Sn film was prepared by magnetron sputtering, and the LaF₃ film was prepared by thermal resistance evaporation.

Through pretreatments, the sensor’s response signal to 40% oxygen concentration was enhanced from 1.9 mV to 46.0 mV at 30°C and 97.0% RH. Tests at temperatures from 30°C to 50°C and humidity from 32.4% RH to 97.0% RH indicated that the output electromotive force (EMF) has a linear relationship with the logarithm of the oxygen concentration. The sensitivity of the sensor increases with an increase in both humidity and temperature in the couple mode, and the EMF of the sensor follows well with the Nernst equation at different temperatures and humidity.

This research could be applied to monitor the oxygen concentration below 25% in confined spaces at room temperature safely without a power supply.

The relationship between temperature and humidity coupling and the response of the sensor was obtained. The nano-film material was integrated with the MEMS process. It is expected to be practically applied in the future.