Piezoresistive Pressure Sensor Research Articles

Formulation analysis and follow-up study of multi-turn configuration for performance enhancement of MEMS piezoresistive pressure sensor utilized for low-pressure measurement applications

Purpose The purpose of this research is to study the performance of piezoresistive pressure sensors using polysilicon as the piezoresistive material, which is typically used to measure pressure in high-temperature environments. Design/methodology/approach The performance of this sensor is enhanced by studying the influence of multi-turn configuration at which the piezoresistors are arranged. Different configurations are studied and compared by laying down their analytical solution. Findings The validation of analytical results is accomplished through finite element analysis using the software COMSOL Multiphysics. The best configuration, which uses a partial triple-turn configuration, was able to achieve a sensitivity of 116.00 mV/V/MPa over a simulated pressure range of 0 to 500 KPa. Originality/value The literature shows the study of single-turn and double-turn meander-shaped configuration of micro-electromechanical systems piezoresistive pressure sensor but multi-turn meander-shaped configuration using a square silicon diaphragm has not been reported. Its study has reflected promising results than its counterparts based on key performance parameters such as sensitivity and linearity and are more effective to be used for automotive, aviation, biomedical and consumer electronics applications.

Flexible Nanofiber Pressure Sensors with Hydrophobic Properties for Wearable Electronics

In recent years, flexible pressure sensors have received considerable attention for their potential applications in health monitoring and human–machine interfaces. However, the development of flexible pressure sensors with excellent sensitivity performance and a variety of advantageous characteristics remains a significant challenge. In this paper, a high-performance flexible piezoresistive pressure sensor, BC/ZnO, is developed with a sensitive element consisting of bacterial cellulose (BC) nanofibrous aerogel modified by ZnO nanorods. The BC/ZnO pressure sensor exhibits excellent mechanical and hydrophobic properties, as well as a high sensitivity of −15.93 kPa−1 and a wide range of detection pressure (0.3–20 kPa), fast response (300 ms), and good cyclic durability (>1000). Furthermore, the sensor exhibits excellent sensing performance in real-time monitoring of a wide range of human behaviors, including mass movements and subtle physiological signals.

Novel Polyurethane Based, Fully Flexible, High-Performance Piezoresistive Sensor for Real-Time Pressure Monitoring.

Flexible piezoresistive pressure sensors are garnering substantial attention, in line with advancements in biointegrated and wearable electronics. However, a significant portion of piezoresistive pressure sensors suffer from the trade-off between sensitivity and pressure range. Moreover, the current piezoresistive sensors generally rely on a rigid metallic electrode, severely deteriorating their long-term durability. Herein, a fully flexible piezoresistive sensor coupling polyurethane (PU) based electrode and active sensing element is proposed to circumvent the aforementioned problems. By rationally regulating the double-permeable conductive networks within the PU matrix, an elastomeric electrode and sensing element are implemented, respectively. The assembled heterostructured configurations enable impressive sensitivity up to 7.023 kPa-1, broad pressure detection (up to 420 kPa), an ultralow pressure sensing limit (0.1 Pa), and extraordinary operation stability over 80000 cyclic pressings along with fast response/relaxation times (60 ms/80 ms). Additionally, the fully flexible sensor is capable of both real-time detection of physiological signals and mimicking keyboards, implying its viability as a high-performance pressure sensor.

Design, fabrication and experimental analysis of piezoresistive bidirectional acoustic sensor

PurposeIdentification of the direction of the sound source is very important for human–machine interfacing in the applications such as target detection on military applications and wildlife conservation. Considering its vast applications, this study aims to design, simulate, fabricate and test a bidirectional acoustic sensor having two cantilever structures coated with piezoresistive material for sensing has been designed, simulated, fabricated and tested.Design/methodology/approachThe structure is a piezoresistive acoustic pressure sensor, which consists of two Kapton diaphragms with four piezoresistors arranged in Wheatstone bridge arrangement. The applied acoustic pressure causes diaphragm deflection and stress in diaphragm hinge, which is sensed by the piezoresistors positioned on the diaphragm. The piezoresistive material such as carbon or graphene is deposited at maximum stress area. Furthermore, the Wheatstone bridge arrangement has been formed to sense the change in resistance resulting into imbalanced bridge and two cantilever structures add directional properties to the acoustic sensor. The structure is designed, fabricated and tested and the dimensions of the structure are chosen to enable ease of fabrication without clean room facilities. This structure is tested with static and dynamic calibration for variation in resistance leading to bridge output voltage variation and directional properties.FindingsThis paper provides the experimental results that indicate sensor output variation in terms of a Wheatstone bridge output voltage from 0.45 V to 1.618 V for a variation in pressure from 0.59 mbar to 100 mbar. The device is also tested for directionality using vibration source and was found to respond as per the design.Research limitations/implicationsThe fabricated devices could not be tested for practical acoustic sources due to lack of facilities. They have been tested for a vibration source in place of acoustic source.Practical implicationsThe piezoresistive bidirectional sensor can be used for detection of direction of the sound source.Social implicationsIn defense applications, it is important to detect the direction of the acoustic signal. This sensor is suited for such applications.Originality/valueThe present paper discusses a novel yet simple design of a cantilever beam-based bidirectional acoustic pressure sensor. This sensor fabrication does not require sophisticated cleanroom for fabrication and characterization facility for testing. The fabricated device has good repeatability and is able to detect the direction of the acoustic source in external environment.

Flexible piezoresistive pressure sensor based on a graphene-carbon nanotube-polydimethylsiloxane composite

Flexible sensors are used widely in wearable devices, specifically flexible piezoresistive sensors, which are common and easy to manipulate. However, fabricating such sensors is expensive and complex, so proposed here is a simple fabrication approach involving a sensor containing microstructures replicated from a sandpaper template onto which polydimethylsiloxane containing a mixture of graphene and carbon nanotubes is spin coated. The surface morphologies of three versions of the sensor made using different grades of sandpaper are observed, and the corresponding pressure sensitivities and linearity and hysteresis characteristics are assessed and analyzed. The results show that the sensor made using 80-mesh sandpaper has the best sensing performance. Its sensitivity is 0.341 kPa−1 in the loading range of 0–1.6 kPa, it responds to small external loading of 100 Pa with a resistance change of 10%, its loading and unloading response times are 0.126 and 0.2 s, respectively, and its hysteresis characteristic is ∼7%, indicating that the sensor has high sensitivity, fast response, and good stability. Thus, the presented piezoresistive sensor is promising for practical applications in flexible wearable electronics.

Batch fabrication of ultrathin flexible pressure sensors enabled by full printed technique

Flexible pressure sensors have gained significant attention in recent years owing to their versatile applications in health monitoring, human-machine interfaces, and artificial robotics. Geometric microengineering of the active layer, including micropatterned structures, porous layers, and multilayered packed structures has been investigated to improve the sensing performance. However, accompanying challenges such as increased thickness and difficulties in achieving mass production still persist. This work presents a full printed technique for fabricating high-performance piezoresistive pressure sensors. Thermal-treated graphene oxide (TGO) colloid was selected as the printing ink. Combined with an in-situ chemical foaming strategy, structural microengineering of the piezoresistive layer was achieved. The obtained hierarchical protruding micro-domes endow the piezoresistive pressure sensors with a wide sensing range of 550 kPa and ultrathin features (18 μm). In addition, the full-printed manufacturing method enables the batch-producible fabrication of pressure sensors. These sensors can be employed for human motion detection and pressure mapping applications.

Flexible polydimethylsiloxane pressure sensor with micro-pyramid structures and embedded silver nanowires: A novel application in urinary flow measurement

Flexible pressure sensors are lightweight and highly sensitive, making them suitable for use in small portable devices to achieve precise measurements of tiny forces. This article introduces a low-cost and easy-fabrication strategy for piezoresistive flexible pressure sensors. By embedding silver nanowires into a polydimethylsiloxane layer with micro-pyramids on its surface, a flexible pressure sensor is created that can detect low pressure (17.3 Pa) with fast response (<20 ms) and high sensitivity (69.6 mA kPa−1). Furthermore, the pressure sensor exhibits a sensitive and stable response to a small amount of water flowing on its surface. On this basis, the flexible pressure sensor is innovatively combined with a micro-rotor to fabricate a novel urinary flow-rate meter (uroflowmeter), and results from a simulated human urination experiment show that the uroflowmeter accurately captured all the essential shape characteristics that were present in the pump-simulated urination curves. Looking ahead, this research provides a new reference for using flexible pressure sensors in urinary flow-rate monitoring.

Optimising polyurethane/CNTs piezoresistive pressure sensors by varying the modulus of the polymer matrix

Varying the elastic modulus of the thermoplastic polyurethane (TPU) matrix on the sensing behaviour of pressure sensors made from TPU/carbon nanotubes (CNTs) elastomeric composites was studied. Piezoresistive sensors have a wide range of applications in wearable devices such as smart shoe insoles. Compounds were prepared using different grades of TPU with various levels of hardness, ranging from 37 to 98 Shore A, using a melt extrusion technique. The percolation threshold of CNTs was about 2 wt%, with the best sensing performance being at a weight fraction above this, at 2.5 wt% CNTs. The elastomeric nanocomposites were characterised for their pressure sensing behaviour. Sensors were constructed by assembling the composite films and an interdigitated silver electrode, and their sensing properties were characterised using a voltage divider circuit under cyclical loading. This work evaluates the reference resistor-dependency, test frequency-dependency and the long-term stability under cyclic loading. The results indicate that the polymer modulus has a significant impact on the sensing performance and piezoresistive hysteresis value for each sensor. As the modulus increases, the hysteresis value between loading-unloading is reduced and the sensor displays a much more stable response during longer cyclical loading tests.

Piezoresistive pressure sensor based on conductive MWCNTs@PANI fiber network for motion sensing and human–machine interface

AbstractWearable smart sensors have broad prospects in medical health and physical exercise. In this study, the core–shell conductive fiber membrane was prepared by adding multiwalled carbon nanotubes during polymerization of aniline on spun fibers. In comparison to the conventionally utilized polymerized aniline, the integration of carbon nanotube particulates enhances the conductivity and surface area, provides more aniline polymerization sites, and simultaneously increases the stability of the composite film. The pressure sensor has a sensitivity of 61.12, 40.32, and 23.17 kPa−1 in the range of 0–7.1 kPa, 7.1–11.1 kPa, and 11.1–19.54 kPa. In addition, it has a fast response time (loading time of 120 ms and unloading time of only 22 ms) and exhibits excellent cyclic stability through numerous loading–unloading cycles. These properties enable the sensor to be applied to real‐time monitoring of human sports health, such as knee and elbow bending, mouse clicking, beaker holding, and so on. This research method provides a new strategy and technology for conducting polymers as materials for flexible electronic equipment.

Perpendicularly assembled oriented electrospinning nanofibers based piezoresistive pressure sensor with wide measurement range

Perpendicularly assembled oriented electrospinning nanofibers based piezoresistive pressure sensor with wide measurement range

High Sensitivity and Wide Linear Range Flexible Piezoresistive Pressure Sensor with Microspheres as Spacers for Pronunciation Recognition.

Flexible piezoresistive pressure sensors have received great popularity in flexible electronics due to their simple structure and promising applications in health monitoring and artificial intelligence. However, the contradiction between sensitivity and detection range limits the application of the sensors in the medium-pressure regime. Here, a flexible piezoresistive pressure sensor is fabricated by combining a hierarchical spinous microstructure sensitive layer and a periodic microsphere array spacer. The sensor achieves high sensitivity (39.1 kPa-1) and outstanding linearity (0.99, R2 coefficient) in a medium-pressure regime, as well as a wide range of detection (100 Pa-160.0 kPa), high detection precision (<0.63‰ full scale), and excellent durability (>5000 cycles). The mechanism of the microsphere array spacer in improving sensitivity and detection range was revealed through finite element analysis. Furthermore, the sensors have been utilized to detect muscle and joint movements, spatial pressure distributions, and throat movements during pronouncing words. By means of a full-connect artificial neural network for machine learning, the sensor's output of different pronounced words can be precisely distinguished and classified with an overall accuracy of 96.0%. Overall, the high-performance flexible pressure sensor based on a microsphere array spacer has great potential in health monitoring, human-machine interface, and artificial intelligence of medium-pressure regime.

An Ultra-low Thermal Sensitivity Drift Piezoresistive Pressure Sensor Compensated by Passive Resistor/Thermistor Network

This paper presents a piezoresistive pressure sensor that exhibits extremely low thermal sensitivity drift across a broad range of temperatures, which integrates a passive resistor/thermistor network for compensation. Standard microfabrication processes were conducted to fabricate the sensor chip. From the experimental results, the proposed sensor demonstrated an extremely low thermal sensitivity drift of 0.01% FS/°C within temperature range of -55 °C to 85 °C, which is a significant improvement compared with the sensor with no temperature compensation (0.17% FS/°C) and the sensor with conventional temperature compensation (0.09% FS/°C). The compensation method developed in this study has the potential to serve as a facilitating instrument in pressure measurements with large temperature variations.

Thermal Compensation System for Silicon Piezoresistive Pressure Sensors Based on Surface Fitting and Wild Horse Algorithm

Thermal Compensation System for Silicon Piezoresistive Pressure Sensors Based on Surface Fitting and Wild Horse Algorithm

From wires to waves, a novel sensor system for in vivo pressure monitoring.

Pressure monitoring in various organs of the body is essential for appropriate diagnostic and therapeutic purposes. In almost all situations, monitoring is performed in a hospital setting. Technological advances not only promise to improve clinical pressure monitoring systems, but also engage toward the development of fully implantable systems in ambulatory patients. Such systems would not only provide longitudinal time monitoring to healthcare personnel, but also to the patient who could adjust their way-of-life in response to the measurements. In the past years, we have developed a new type of piezoresistive pressure sensor system. Different bench tests have demonstrated that it delivers precise and reliable pressure measurements in real-time. The potential of this system was confirmed by a continuous recording in a patient that lasted for almost a day. In the present study, we further characterized the functionality of this sensor system by conducting in vivo implantation experiments in nine female farm pigs. To get a step closer to a fully implantable system, we also adapted two different wireless communication solutions to the sensor system. The communication protocols are based on MICS (Medical Implant Communication System) and BLE (Bluetooth Low Energy) communication. As a proof-of-concept, implantation experiments in nine female pigs demonstrated the functionality of both systems, with a notable technical superiority of the BLE.

Highly Sensitive and Breathability Flexible Piezoresistive Pressure Sensor Based on Xylon

AbstractIn recent years, the prevalence of cervical spondylosis has been increasing, which is associated with unhealthy posture in daily life, flexible pressure sensors are beneficial in preventing cervical spine disorders. This work is dedicated to developing a flexible, high‐performance, and breathable device to monitor the health of the neck. Here, a flexible pressure sensor with a “sandwich” structure is presented, which incorporates patterned xylon fabric as the substrate and MXene as the sensitive layer. Furthermore, the application of silver nanowires (AgNWs) as the electrode material improves the piezoresistive performance. Combined with an internal elastic encapsulation method (IEEM), the sensor exhibits high sensitivity (1417.9 kPa−1 under pressure below 100 kPa) and a fast response time (30.77 ms). Compared with traditional flexible pressure sensors, the breathability of devices with an all‐fiber structure is nearly seven times higher, which better satisfies the monitoring requirements of long‐term wear. Finally, a wireless system is established by integrating a Bluetooth module and a terminal app. It enables monitoring and sensing of various physiological signals of the neck, as well as identification and alerting of long‐term poor posture such as prolonged neck flexion, showing a potential candidate for the applications of the next‐generation wearable device.

Improved Sensitivity of MEMS-based Piezoresistive Pressure Sensor using Silicon Nitride Diaphragm

In this paper, Piezoresistive Pressure Sensor (PPS) with four Polysilicon piezoresistors on Si3N4 diaphragm with improved sensitivity is successfully designed by using MEMS technology. Sensing is accomplished via deposited polysilicon resistors like metal resistors. The analytical model of PPS is optimized for location and geometry of the piezoresistors and the sensors based on different aspect ratios (both square and rectangular) have been investigated. The performance parameters like maximum deflection, maximum induced stress on the diaphragm have been compared using ANSYS and MATLAB simulation programming based on mathematical model. By interpreting the proper selection of the geometry of a thin Si3N4 diaphragm, the maximum deflection, maximum induced stress and highest sensitivity for this sensor are obtained for the diaphragm when aspect ratio is minimum. It has been found that sensitivity of the sensor is achieved when the piezoresistors are symmetrically placed at 65 m from the edges of the diaphragm. The analysis describes that the sensor based on square diaphragm is more sensitive than the rectangular one. It is influenced more powerfully by diaphragm thickness. The applied pressure range is considered from 0.5 kPa to 40 kPa. From the simulation results, the shape and the sensor design can be optimized for a highly sensitive PPS.

Artificial Tactile Sensing Neuron with Tactile Sensing Ability Based on a Chitosan Memristor.

Owing to the highly parallel network structure of the biological neural network and its triggered processing mode, tactile sensory neurons can realize the perception of external signals and the functions of perception, memory, and data processing by adjusting the synaptic weight. In this paper, a piezoresistive pressure sensor is combined with a memristor to design an artificial tactile sensory neuron. The polyurethane sponge sensor has excellent sensitivity and can convert physical stimuli into electrical signals, and the chitosan-based memristor has stable bipolar resistive switching characteristics, allowing further information to be memorized and processed. The neuron can respond to tactile stimuli of different degrees, durations, and frequencies; realize potentiation/depression modulation, paired-pulse facilitation, and spike-timing-dependent plasticity; exhibit spike-rate-dependent plasticity; and store and erase tactile information through memistor state switching, which has great application potential in biological sensing systems.

3D Printing of Anisotropic Piezoresistive Pressure Sensors for Directional Force Perception.

Anisotropic pressure sensors are gaining increasing attention for next-generation wearable electronics and intelligent infrastructure owing to their sensitivity in identifying different directional forces. 3D printing technologies have unparalleled advantages in the design of anisotropic pressure sensors with customized 3D structures for realizing tunable anisotropy. 3D printing has demonstrated few successes in utilizing piezoelectric nanocomposites for anisotropic recognition. However, 3D-printed anisotropic piezoresistive pressure sensors (PPSs) remain unexplored despite their convenience in saving the poling process. This study pioneers the development of an aqueous printable ink containing waterborne polyurethane elastomer. An anisotropic PPS featuring tailorable flexibility in macroscopic 3D structures and microscopic pore morphologies is created by adopting direct ink writing 3D printing technology. Consequently, the desired directional force perception is achieved by programming the printing schemes. Notably, the printed PPS demonstrated excellent deformability, with a relative sensitivity of 1.22 (kPa* wt. %)-1 over a substantial pressure range (2.8 to 8.1kPa), approximately fivefold than that of a state-of-the-art carbon-based PPS. This study underscores the versatility of 3D printing in customizing highly sensitive anisotropic pressure sensors for advanced sensing applications that are difficult to achieve using conventional measures.

High-sensitivity, ultrawide linear range, antibacterial textile pressure sensor based on chitosan/MXene hierarchical architecture

It is still a great challenge for the flexible piezoresistive pressure sensors to simultaneously achieve wide linearity and high sensitivity. Herein, we propose a high-performance textile pressure sensor based on chitosan (CTS)/MXene fiber. The hierarchical "point to line" architecture enables the pressure sensor with high sensitivity of 1.16kPa-1 over an ultrawide linear range of 1.5 MPa. Furthermore, the CTS/MXene pressure sensor possesses a low fatigue over 1000 loading/unloading cycles under 1.5 MPa pressure load, attributed to the strong chemical bonding between CTS fiber and MXene and excellent mechanical stability. Besides, the proposed sensor shows good antibacterial effect benefiting from the strong interaction between polycationic structure of CTS/MXene and the predominantly anionic components of bacteria surface. The sensor is also applied to detect real-time human action, an overall classification accuracy of 98.61% based on deep neural network-convolutional neural network (CNN) for six human actions is realized.

Innovative Silicon-Ceramic (SiCer) Technology for High-Strength Pressure Sensor Applications Using Different Manufacturing Methods

A variety of manufacturing methods can be used to assemble silicon-based piezoresistive pressure sensors, such as anodic bonding or silicon direct bonding. To achieve highstrength pressure sensors, a high quality interface connection is required. The combination of silicon and ceramic creates a new innovative composite system known as Silicon-on-Ceramics, short SiCer. By using a special developed bondable Low Temperature Co-fired Ceramic tape, which corresponds to the thermal expansion coefficient of Si, the combination of both materials is possible through a sintering process. Advantages of the SiCer technology are high temperature stability, manufacturing at wafer-level and a high bond strength at the interface. Different manufactured SiCer-based pressure sensors were fabricated, electrically and mechanically characterized and compared with anodic bonded and silicon direct bonded pressure sensors.