Robust Pressure Sensor Research Articles

Temperature-Immune, Wide-Range Flexible Robust Pressure Sensors for Harsh Environments.

Flexible pressure sensors possess vast potential for various applications such as new energy batteries, aerospace engines, and rescue robots owing to their exceptional flexibility and adaptability. However, the existing sensors face significant challenges in maintaining long-term reliability and environmental resilience when operating in harsh environments with variable temperatures and high pressures (∼MPa), mainly due to possible mechanical mismatch and structural instability. Here, we propose a composite scheme for a flexible piezoresistive pressure sensor to improve its robustness by utilizing material design of near-zero temperature coefficient of resistance (TCR), radial gradient pressure-dividing microstructure, and flexible interface bonding process. The sensing layer comprising multiwalled carbon nanotubes (MWCNTs), graphite (GP), and thermoplastic polyurethane (TPU) was optimized to achieve a near-zero temperature coefficient of resistance over a temperature range of 25-70 °C, while the radial gradient microstructure layout based on pressure division increases the range of pressure up to 2 MPa. Furthermore, a flexible interface bonding process introduces a self-soluble transition layer by direct-writing TPU bonding solution at the bonding interface, which enables the sensor to achieve signal fluctuations as low as 0.6% and a high interface strength of up to 1200 kPa. Moreover, it has been further validated for its capability of monitoring the physiological signals of athletes as well as the long-term reliable environmental resilience of the expansion pressure of the power cell. This work demonstrates that the proposed scheme sheds new light on the design of robust pressure sensors for harsh environments.

All textile-based robust pressure sensors for smart garments

Textile-based pressure sensors with good comfortness and breathability can be easily integrated into garments for smart wearables. Nevertheless, scalable construction of all textile-based pressure sensors with good mechanical robustness and desirable sensor performance still remains a great challenge. Here, a facile, low-cost, and scalable approach is proposed to fabricate a new paradigm of all textile-based and mechanically robust pressure sensors. These pressure sensors consist of a top elastic piezoresistive sensing fabric and a bottom textile-based robust interdigital electrodes. The top piezoresistive sensing fabric is fabricated by controllably depositing robust polyurethane/carbon nanotubes composites on a highly elastic Venetian fabric through electrostatic layer-by-layer assembly. The bottom interdigital electrodes are prepared by screen printing of an elastic and robust carbon ink on a polyester fabric. Notably, the conductive networks in both of the piezoresistive sensing layer and the bottom electrodes are firmly embedded in elastomer substrates rather than directly attached onto the fabric surface, endowing the pressure sensors with superior mechanical robustness. The as-fabricated all textile-based pressure sensors exhibit high sensitivity (3.42 kPa−1), fast response/recovery time (32 ms/4 ms), good cycling stability (10 000 cycles), superior robustness against mechanical bending (10 000 cycles) and chemical washing. As demonstrations, the pressure sensors are integrated into diverse garments for wireless and real-time monitoring of various human physiological activities, including joint bending, muscle activity, object grasping, etc. This proposed simple but efficient approach for fabricating all textile-based pressure sensors with superior robustness opens up new opportunities for the further development of smart garments and wearable devices.

Piezoionic transfer effect in topological borophene-bismuthene derivative micro-leaves for robust supercapacitive electronic skins

To gain high performance in electrochemical device, exquisite accelerating ion-electron transfer is an effective way. Here, a topological idea is realized to design a micro-leave electrode by patterning borophene-bismuthene derivative. The inner bismuthene offers high conductive skeleton, intermediate BiOCl and Bi2O3 derivative as ornament contribute to supercapacitive property, and the outer borophene layer not only boosts supercapacitive property, but also reserves the topological shape. Assisted by a hydrogel electrolyte on a flexible indium-doped tin oxide substrate, a robust pressure sensor is fabricated, in which a piezoionic transfer effect is demonstrated to induce fast ions extraction and migration kinetics among the topological micro-leaves. Then the specific capacitance of electrode increases by 2.483 times comparing with the micro-leaves without borophene. The resultant robust electronic skin sensor presents a comparable sensitivity of 1.60 kPa−1 in the tiny pressure range of ≈ 50–150 Pa, and sensitivity of 1.01 kPa−1 in 150 Pa-8.5 kPa, low detection limit as 0.59 Pa, fast response/recovery time (80/80 ms), wide detection range (∼220 kPa) and reliable capacitance retention of 97.92% even after 10000 cycles. This has been successfully used to monitor the physiological signals and illustrates potential application prospects in human-computer interaction.

Robust Pressure Sensor in SOI Technology with Butterfly Wiring for Airfoil Integration.

Current research in the field of aviation considers actively controlled high-lift structures for future civil airplanes. Therefore, pressure data must be acquired from the airfoil surface without influencing the flow due to sensor application. For experiments in the wind and water tunnel, as well as for the actual application, the requirements for the quality of the airfoil surface are demanding. Consequently, a new class of sensors is required, which can be flush-integrated into the airfoil surface, may be used under wet conditions—even under water—and should withstand the harsh environment of a high-lift scenario. A new miniature silicon on insulator (SOI)-based MEMS pressure sensor, which allows integration into airfoils in a flip-chip configuration, is presented. An internal, highly doped silicon wiring with “butterfly” geometry combined with through glass via (TGV) technology enables a watertight and application-suitable chip-scale-package (CSP). The chips were produced by reliable batch microfabrication including femtosecond laser processes at the wafer-level. Sensor characterization demonstrates a high resolution of 38 mVV−1 bar−1. The stepless ultra-smooth and electrically passivated sensor surface can be coated with thin surface protection layers to further enhance robustness against harsh environments. Accordingly, protective coatings of amorphous hydrogenated silicon nitride (a-SiN:H) and amorphous hydrogenated silicon carbide (a-SiC:H) were investigated in experiments simulating environments with high-velocity impacting particles. Topographic damage quantification demonstrates the superior robustness of a-SiC:H coatings and validates their applicability to future sensors.

Piezotronic effect in a normally off p-GaN/AlGaN/GaN HEMT toward highly sensitive pressure sensor

We report the effect of stress or strain on the electronic characteristics of a normally off AlGaN/GaN high electron mobility transistor (HEMT) and demonstrate its role as a highly sensitive pressure sensor. We observe that the HEMT drain current exhibits a linear change of 2.5%/bar upon the application of pressure, which is translated to a strain sensitivity of 1250 ppm−1. This is the highest strain sensitivity ever reported on HEMTs and many other conventional strain sensing configurations. The relative change of drain current is largest when the gate bias is near-threshold and drain bias is slightly larger than the saturation bias. The electron sheet density and mobility changes in the AlGaN/GaN heterointerface under the applied pressure or mechanical strain are explained qualitatively. The spontaneous and piezoelectric-polarization-induced surface and interface charges in the AlGaN/GaN heterojunction can be used to develop very sensitive and robust pressure sensors. The results demonstrate a considerable potential of normally off AlGaN/GaN HEMTs for highly sensitive and reliable mechanical sensing applications with low energy consumption.

Design and implementation of smart pressure sensor for automotive applications

No doubt that the measurement is an important matter in the precise and accurate control of automotive subsystems to improve the performance and efficiency. The key tool to achieve high degree of precision and accuracy in control applications is sensor. In recent years, the rapid technological advances have revolutionized the automotive industry and a great variety of new sensors are introduced to the market with the purpose of accelerating the development of autonomous vehicles technology. However, the increasing legal pressures from regulatory authorities have led to strengthened requirements for robust pressure sensors in vehicles. On the other hand, the cost of such devices need to remain low due to the continual competition in the market. In this study, we have proposed a low cost piezoresistive sensing method based smart pressure sensor, which combines the signal conditioning, analog/digital signal processing and communication circuitry directly to the sense element in a single compact housing. The introduced smart pressure sensor achieves the improved reliability and greater accuracy due to its built-in temperature compensation, filtering and self-calibration capabilities. The measurement performance of our prototype design has been tested in dynamic test device, which can control the working status of a typical vehicle compressor. The experimental results validate the robustness of the proposed smart pressure sensor in terms of linearity, repeatability and data transmission.

Enhanced Energy Harvesting Ability of ZnO/PAN Hybrid Piezoelectric Nanogenerators.

Miniaturization of energy conversion and storage devices has attracted remarkable consideration in the application of wearable electronics. Compared with film-based flexible electronics, fiber-based wearable electronics (e.g., nanogenerators and sensors made from electrospun nanofibers) are more appealing and promising for wearables. However, there are two bottlenecks, a low power output and poor sensing capability, limiting the application of piezoelectric nanofibers. Herein, we integrated zinc oxide nanorods (ZnO NRs) to a less known piezoelectric polymer, polyacrylonitrile (PAN) nanofiber, forming a ZnO/PAN nanofabric, which significantly improved the pressure sensitivity and vibrational energy harvesting ability by about 2.7 times compared with those of the pristine PAN nanofiber, and the maximum output power density of ∼10.8 mW·m-2 is achieved. Noteworthily, the ZnO/PAN nanofabric showed a power output about twice of the one made of ZnO and polyvinylidene fluoride. It was revealed that the integration of ZnO NRs clearly improved the planar zigzag conformation in microstructures of the PAN nanofiber. Further, successful demonstrations of a mechanically robust pressure sensor and wearable power source confirm the potential applications in human activity monitoring and personal thermal management, respectively.

A robust stretchable pressure sensor for electronic skins

As an essential role in electronic skins, flexible pressure sensors have attracted wide attention for their applications in human-machine interaction and intelligent prosthetic, etc. Whereas, in general, it is difficult for most flexible pressure sensors to acquire high accuracy, especially under multi-modal interference (temperature, humidity and deformation). Herein, a novel stretchable flexible pressure sensor was presented by direct writing, which was capable of weakening the strain effect, fending off humidity interference and restraining thermal influence by using a double layer raised island structure substrate, a covering layer and a Wheatstone bridge-configuration of the sensing element. The sensor kept robust under multi-modal interference of strain about 0–20%, temperature of 30–80 °C and humidity in 20–90%, owning high and stable sensitivity of 2.6 kPa −1 –14.05 kPa −1 under 0–74 kPa. Two demonstrations of grabbing a bottle with different temperatures and a kid's catching behavior on a opisthenar of a carer verified that such sensor possessed a great potential in many non-structured applications and will be a promising candidate for stretchable flexible pressure sensors in future. • A robust pressure sensor which can restrain the interference of deformation, temperature and humidity was presented. • A double layer raised island structure substrate was used to weaken the strain effect. • A Wheatstone bridge configuration of four same sensing elements was elaborated to eliminate the thermal impact. • Two applications including grabbing a bottle and a kid's catching behavior have been demonstrated.

Realization of a micro composite based pressure sensor: Its performance study for linearity, hysteresis and sensitivity

The relevance of pressure sensors in daily life applications has been phenomenal in diversified disciplines such as engineering, bio-medical, automobile, aerospace etc. Making right choice of pressure sensors is crucial in any of these disciplines. Of late, the pursuit of making the pressure sensors applicable to various domains has spurred a variety of innovative activities. They are being fabricated using novel materials and unconventional fabrication methodology. Also, the advent of microelectromechanical systems has provided new horizons for a variety of realizations that led to the development of efficient and robust pressure sensors. The electromechanical characteristics of the sensing materials and the fabrication methodologies employed to realize the sensor have significant influence on performance of the sensor. This paper reports the micro composite based piezoresistive gauge pressure sensor performance study which was realized by screen printing technique. Graphite-PVC resin based dispersions are screen printed on flat, circular shaped, 1.98 mm thick stainless-steel diaphragm. The transducing layers are directly printed on the deforming polymer coated diaphragm so that the coupling factor is high, resulting in an efficient transfer of strain. Pressure cyclic study and its effect on linearity, hysteresis, sensitivity, stability etc. are investigated. The sensitivity is found to be 0.357 mV/bar. The maximum hysteresis and non-linearity are found to be less than 0.8% FSO. A fairly satisfactory sensitivity, linearity, hysteresis and stability are accomplished at a low cost. By observing the performance characteristics of the realized pressure sensor it can be used in commercial, industrial, automotive, aerospace and strategic fields. Some of the applications could be in tire pressure sensing, air filling in petrol bunks, petrol/diesel/oil/water tankers, water supply pipelines, oil/gas explorations, hydraulic jacks and mines etc.

Large-Area Carbon Nanotube-Based Flexible Composites for Ultra-Wide Range Pressure Sensing and Spatial Pressure Mapping.

Flexible pressure sensors are of broad interest for applications including human-machine interfaces, wearable electronics, and object/motion detection. However, complexities associated with constituent materials, fabrication processes, sensing mechanisms, and hardwiring often hinder the large-scale applications of using high performance pressure sensors reported in the literature. Here we demonstrate a large-area, highly flexible, conformable, and mechanically robust pressure sensor using a silicone elastomer with an embedded nonwoven textile carrier coated with carbon nanotubes. The selected silicone polymer allows through-thickness deformability of the sensor while the high modulus textile carrier ensures in-plane stiffness and stability. The sensor has an initial electrical conductivity of 4.4 ± 0.38 S/m and is fabricated using a straightforward dip coating and polymer infusion process and can be easily scaled-up for large-scale applications. On the basis of its hierarchical composite structure, this piezoresistive pressure sensor possesses extremely high resilience under compression, a repeatable monotonic positive pressure correlation, and an ultrawide elastic working range (5.5 ± 0.5 MPa) that can be segmentally linearized. A true two-dimensional modality for spatial pressure mapping is realized by utilizing electrical impedance tomography (EIT) and demonstrated to yield conductivity maps that can estimate the location, shape, and amplitude of both localized and distributed pressure with simple contact areas.

Sensing up to 40 atm Using Pressure‐Sensitive Aero‐GaN

This work reports on the fabrication and characterization of a robust pressure sensor based on aero‐GaN. The ultraporous aeromaterial consists of GaN interconnected hollow micro‐tetrapods with the wall thickness of about 70 nm. The inner surface of hollow micro‐tetrapods contains an ultrathin film of ZnO genetically related to the sacrificial template used for epitaxial deposition of GaN. The pressure sensing measurements disclose a nearly linear dependence of the electrical conductance versus applied pressure up to 40 atm, a stable state signal being attained after an interval of about 10 s.

Fabrication of N-doped 3C-SiC nanobelts with selected [formula omitted] top surface and their enhanced transverse piezoresistance behaviours

The piezoresistive effect of SiC low-dimensional nanostructures, together with their exclusive benefits of superior mechanical characteristics and could be integrated into the flexible devices that can withdraw large strain, promise to make a wide range of sensing devices application possible in the severe working conditions. In this work, we reported the transverse piezoresistance behaviours of n-type 3C-SiC nanobelts with selected (11¯0) top surface and N dopants. The single-crystalline SiC nanobelts were achieved by the means of direct pyrolysis of polymeric precursors without catalysts, which had an average N doping level of ~ 6.02 at% and a typical width-to-thickness ratio of ~ 8. It was disclosed that the transverse piezoresistance coefficient π[11¯0] reached the maximum 10.29 × 10–11 Pa−1 at a fixed external stress of 67.03 nN. Correspondingly, the gauge factor (GF) was calculated to be of ~ 61.7, which is higher than all the reported n-type SiC, intrinsic SiC, as well as most of the p-type SiC counterparted. The findings shed light on the fact that present n-type SiC nanobelts have the potential of becoming an outstanding contestant for the development of robust pressure sensors having elevated sensitivities.

Thermomechanical stability and integrability of an embedded ceramic antenna with an integrated sensor element for wireless reading in harsh environments

This paper reports on the design, manufacturing and evaluation of a small, wirelessly powered and read resonating antenna circuit with an integrated pressure sensor. The work aims at developing miniature devices suitable for harsh environments, where high temperature prevents the use of conventional, silicon-based microdevices. Here, the device is made of alumina with platinum as conducting material. Ceramic green tapes were structured using high-precision milling, metallized using screen printing, and subsequently laminated to form stacks before they were sintered. The device's frequency shift as a function of temperature was studied up to 900°C. The contributions to the shift both from the thermomechanical deformation of the device at large, and from the integrated and, so far, self-pressurized sensor were sorted out. A total frequency shift of 3200 ppm was observed for the pressure sensor for heating over the whole range. Negligible levels of thermally induced radius of curvature were observed. With three-point bending, a frequency shift of 180 ppm was possible to induce with a curvature of radius of 220 m at a 10 N load. The results indicate that a robust pressure sensor node, which can register pressure changes of a few bars at 900°C and wirelessly transmit the signal, is viable.

Highly sensitive piezoresistance behaviors of n-type 3C-SiC nanowires

We reported the piezoresistance behaviors of n-type 3C-SiC nanowires, which show that the present SiC nanowires could be an excellent candidate for building robust pressure sensors with high sensitivities.

A robust pressure sensor for harsh environmental applications

Due to economical and environmental requirements there is a strong need both to increase the efficiency and to monitor the actual status of gas turbines, rocket engines and deep drilling systems. For these applications a micromachined pressure sensor based on a sapphire body and a platinum thin film metallization is presented to withstand harsh environments such as high temperature levels, aggressive media and/or high pressure loads. For pre-evaluation purposes, a reusable packing is used enabling the device characterization in a very efficient way up to temperatures of 440°C and pressures of 30bar, respectively. As expected, the output signals of the Wheatstone bridge increase with higher pressures, but decrease with enhanced temperature levels. Furthermore, these characteristics show a sensitivity of about 10μV/(Vbar) in this temperature range and a negative drift in the offset when no pressure load is applied with increasing temperature. This effect is predominantly caused by the mismatch of the temperature coefficients of expansion associated with the device and the housing leading to a pre-stressed membrane.

Design and evaluation process of a robust pressure sensor for measurements in boundary layers of liquid fluids

In this work, the latest results of the design, fabrication and characterization of a new MEMS piezoresistive pressure sensor are presented. Significant changes in the layout as well as in the micro-fabrication process have been made, e.g. anodic bonding of a glass cover on the backside. The sensor has been developed in order to meet the special requirements of measurements in fluid mechanics, particularly with regard to the non-intrusive nature of the sensor. The sensor development, starting with the simulation of mechanical stresses within the diaphragm resulting from a pressure of up to 4 bar is described. These calculations have lead to an optimized placement of the piezoresistors in order to achieve a maximum sensitivity. Important parameters including sensitivity, resonance frequency and maximum load are described precisely. The experiments and the initial results, e.g. its linearity and its dynamic capability are demonstrated.