High-sensitivity Pressure Sensor Research Articles

High sensitivity and broad linearity range pressure sensor based on hierarchical in-situ filling porous structure

Flexible piezoresistive pressure sensor with high sensitivity over a broad linearity range have been attracting tremendous attention for its applications in health monitoring, artificial intelligence, and human-machine interfaces. Herein, we report a hierarchical in-situ filling porous piezoresistive sensor (HPPS) by direct ink writing (DIW) printing and curing of carbon nanofibers (CNFs)/polydimethylsiloxane (PDMS) emulsion. Hierarchical geometry significantly increases the contact area, distributes stress to multilayered lattice and internal porous structure, resulting in a broad sensing range. Moreover, unlike conventional hollow porous structure, the CNFs networks in-situ filling porous structure generates more contact sites and conductive pathways during compression, thereby achieving high sensitivity and linearity over entire sensing range. Therefore, the optimized HPPS achieves high sensitivity (4.7 kPa−1) and linearity (coefficient of determination, R2 = 0.998) over a broad range (0.03–1000 kPa), together with remarkable response time and repeatability. Furthermore, the applications in diverse pressure scenarios and healthcare monitoring are demonstrated.

Digital Light Processing 3D Printing of Tough Supramolecular Hydrogels with Sophisticated Architectures as Impact-Absorption Elements.

Processing tough hydrogels into sophisticated architectures is crucial for their applications as structural elements. However, Digital Light Processing (DLP) printing of tough hydrogels is challenging because of the low-speed gelation and toughening process. Described here is a simple yet versatile system suitable for DLP printing to form tough hydrogel architectures. The aqueous precursor consists of commercial photoinitiator, acrylic acid, and zirconium ion (Zr4+ ), readily forming tough metallo-supramolecular hydrogel under digital light because of in situ formation of carboxyl-Zr4+ coordination complexes. The high-stiffness and antiswelling properties of as-printed gel enable high-efficiency printing to form high-fidelity constructs. Furthermore, swelling-induced morphing of the gel is also achieved by encoding structure gradients during the printing with grayscale digital light. Mechanical properties of the printed hydrogels are further improved after incubation in water due to the variation of local pH and rearrangement of coordination complex. The swelling-enhanced stiffness affords the printed hydrogel with shape fixation ability after manual deformations, and thereby provides an additional avenue to form more complex configurations. These printed hydrogels are used to devise an impact-absorption element or a high-sensitivity pressure sensor as proof-of-concept examples. This work should merit engineering of other tough gels and extend their scope of applications in diverse fields.

High-Sensitivity Pressure Sensors Based on a Low Elastic Modulus Adhesive.

With the rapid development of intelligent applications, the demand for high-sensitivity pressure sensor is increasing. However, the simple and efficient preparation of an industrial high-sensitivity sensor is still a challenge. In this study, adhesives with different elastic moduli are used to bond pressure-sensitive elements of double-sided sensitive grids to prepare a highly sensitive and fatigue-resistant pressure sensor. It was observed that the low elastic modulus adhesive effectively produced tensile and compressive strains on both sides of the sensitive grids to induce greater strain transfer efficiency in the pressure sensor, thus improving its sensitivity. The sensitivity of the sensor was simulated by finite element analysis to verify that the low elastic modulus adhesive could enhance the sensitivity of the sensor up to 12%. The preparation of high-precision and fatigue-resistant pressure sensors based on low elastic modulus, double-sided sensitive grids makes their application more flexible and convenient, which is urgently needed in the miniaturization and integration electronics field.

Nano-Patterned Ionogel Film for High-Sensitivity and Recyclable Flexible Pressure Sensor

Flexible pressure sensors have drawn tremendous attention in the past decades due to their widely advanced applications in electronic skin, intelligent robots and wearable devices. Most existing pressure sensors are developed based on capacitive sensing mechanism, but the sensitivity of such sensors still need to be improved. Herein a high-sensitivity pressure sensor was developed based on the P(VDF-HFP)/[Emim][BF₄] ionogel film. The ionogel film has the characteristics of good mechanical flexibility, good ionic conductivity, high dielectric constant and uniformed nanocone array structure, so the flexible pressure sensor which incorporates it as the dielectric layer shows a high sensitivity (22.38 kPa^−1 within 0–3 kPa, and 15.17 kPa^−1 within 3–15 kPa), fast response (0.29 s) and relaxation (0.16 s) time and good long-term stability. The good solubility of the P(VDF-HFP) copolymer in acetone and the non-crosslinking of the [Emim]^+ and [BF₄]^− within the copolymer network give the ionogel the ability to be recycled, thus endowing the critical component of the pressure sensor with 100% recyclability of structure and function. In addition, the sensor was successfully applied to identify fingertip force and map the pressure distribution of different objects, demonstrating that the pressure sensor can be used as part of wearable devices and human–machine interfaces to sense pressure.

Modulation of Fano-like resonance in spherical microbubble cavity for high sensitivity pressure sensing

In this paper, we demonstrate a simple scheme to achieve Fano-like and electromagnetically induced transparency (EIT) like resonance by changing the coupling position of a high-Q spherical microbubble cavity with tapered fiber. The evolution processes of the Fano-like and EIT-like spectrums are explored from simulation and experiment, which are in good agreement. And a high sensitivity pressure sensor based on Fano-like resonance is realized. It shows that compared with the slopes of the Lorentz lineshape, Fano-like and EIT-like lineshapes are increased by 2.7 and 20.7 times, respectively. It provides a simple method for ultra-high sensitive sensing.

Pomegranate-Inspired Biomimetic Pressure Sensor Arrays With a Wide Range and High Linear Sensitivity for Human–Machine Interaction

Flexible, highly sensitive, easy fabricating process, low-cost pressure sensors are the trend for flexible electronic devices. Despite the tremendous progress in recent years, it is still challenging to prepare pressure sensors with high sensitivity, high stability, and fast responsiveness. In this study, we report a simple and low-cost method for the preparation of novel pressure sensors. Inspired by the pomegranate structure, a 3-D porous structure consisting of polystyrene (PS) microspheres filled with reduced graphene oxide (rGO) paper is proposed. This pressure sensor has high linear sensitivity (1.41 kPa <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> in the pressure range of 0–50 kPa), high stability (1000 cycles), and quick response time (~20 ms). Furthermore, a robotic arm interacting control system based on pressure sensor arrays is constructed, which demonstrates the far-reaching potential of pressure sensors in human–machine interaction. Therefore, this work provides a low-cost and effective method for preparing high linear sensitivity pressure sensors.

High sensitivity and broad detection range flexible capacitive pressure sensor based on rGO cotton fiber for human motion detection

Recently, flexible pressure sensors have attracted considerable interest in electronic skins, wearable devices, intelligent robots and biomedical diagnostics. However, the design of high sensitivity flexible pressure sensors often relies on expensive materials and complex process technology, which greatly limit their popularity and applications. Even worse, chemical-based sensors are poorly biocompatible and harmful to the environment. Here, we developed a flexible capacitive pressure sensor based on reduced graphene oxide cotton fiber by a simple and low-cost preparation process. The environmentally friendly sensor exhibited a comprehensive performance with not only ultra-high sensitivity (up to 15.84 kPa−1) and a broad sensing range (0–500 kPa), but also excellent repeatability (over 400 cycles), low hysteresis (⩽11.6%), low detection limit (<0.1 kPa) and wide frequency availability (sensitivity from 19.71 to 11.24 kPa−1, frequency from 100 Hz to 10 kHz). Based on its superior performance, the proposed sensor can detect various external stimuli (vertical stress, bending and airflow) and has been successfully applied for facial expression recognition, breathing detection, joint movement and walking detection, showing great potential for application in artificial electronic skin and wearable healthcare devices.

High sensitivity temperature and pressure sensor based on cascaded Fabry-Perot and Sagnac interferometers

A sensor was proposed and experimentally demonstrated to improve temperature and pressure sensitivity by the Vernier effect. The sensor is composed of a cascaded Fabry-Perot interferometer (FPI) and a Sagnac interferometer (SI), which has almost the same free spectral range (FSR) forming the Vernier effect. The SI is a fiber-loop consisting of a segment of polarization maintaining fiber (PMF). The FPI consists of a section of quartz capillary inserted between two sections of single mode fiber. A micro-channel is drilled in the quartz capillary using a femtosecond laser to circulate air inside and outside the Fabry-Perot (F-P) cavity. SI and FPI in the sensor structure are selectively sensitive to temperature and pressure. In temperature sensing, the SI acts as the sensor and FPI as the reference, whereas in pressure measurements, the FPI is the sensing unit and SI the reference unit. Thus, in Vernier effect sensing, they perform the functions of reference or sensing units to each other. The sensor provides high sensitivity for both temperature and pressure. Experimental results show that the temperature sensitivity is ∼23.14 nm/°C, which is ∼13.4 times higher for the single SI sensor (–1.73 nm/°C), and the pressure sensitivity is ∼49.2 nm/MPa, which is ∼12.2 times higher than for the single FPI sensor (4.02 nm/MPa). The sensor has a simple structure, easy preparation, and high sensitivity of both temperature and gas pressure, and has widespread prospective application.

Stretchable and anti-impact iontronic pressure sensor with an ultrabroad linear range for biophysical monitoring and deep learning-aided knee rehabilitation

Monitoring biophysical signals such as body or organ movements and other physical phenomena is necessary for patient rehabilitation. However, stretchable flexible pressure sensors with high sensitivity and a broad range that can meet these requirements are still lacking. Herein, we successfully monitored various vital biophysical features and implemented in-sensor dynamic deep learning for knee rehabilitation using an ultrabroad linear range and high-sensitivity stretchable iontronic pressure sensor (SIPS). We optimized the topological structure and material composition of the electrode to build a fully stretching on-skin sensor. The high sensitivity (12.43 kPa−1), ultrabroad linear sensing range (1 MPa), high pressure resolution (6.4 Pa), long-term durability (no decay after 12000 cycles), and excellent stretchability (up to 20%) allow the sensor to maintain operating stability, even in emergency cases with a high sudden impact force (near 1 MPa) applied to the sensor. As a practical demonstration, the SIPS can positively track biophysical signals such as pulse waves, muscle movements, and plantar pressure. Importantly, with the help of a neuro-inspired fully convolutional network algorithm, the SIPS can accurately predict knee joint postures for better rehabilitation after orthopedic surgery. Our SIPS has potential as a promising candidate for wearable electronics and artificial intelligent medical engineering owing to its unique high signal-to-noise ratio and ultrabroad linear range.An ultrabroad-linear range (1 MPa) iontronic pressure sensor with superior sensitivity (12.43 kPa-1) and stretchability (up to 20%) was proposed for biophysical monitoring and deep learning-based knee-rehabilitation training.

High-Temperature and High-Sensitivity Pressure Sensors Based on Microwave Resonators

This paper reports a novel diaphragm-assisted open-ended hollow coaxial cable resonator (OE-HCCR) for highly sensitive pressure measurements at elevated temperatures. The coaxial line resonator is constructed using two highly reflective reflectors in a homemade hollow coaxial cable, including a metal post shorting the two concentric conductors (i.e., the inner conductor and the outer conductor) and the open end of the coaxial line. In the pressure sensor device design, a sealed metal diaphragm is mounted on the open end of the OE-HCCR and is employed as the pressure responsive element. The diaphragm’s deflection can be accurately captured by the coaxial line resonator in real-time, in response to a change in differential pressure. The sensor device’s responses to hydraulic pressures at ambient temperature and air pressures at elevated temperatures up to 1000 °C were investigated in the demonstration experiments, showing user-configurable measurement sensitivity and high-temperature survivability. The device’s pressure measurement resolution is also demonstrated as high as sub-Pascal by probing tiny hydrostatic pressure changes. A positive feedback loop is constructed as an alternative interrogator for the novel device, showing high signal quality and ease of demodulation. The pressure sensor described in this work is robust, easy-to-manufacture, user-configurable, low-cost, highly sensitive, and has great potential for industrial applications involving high-temperature and harsh environments. The presented work opens new avenues to develop a new generation of high-sensitivity and high-temperature microwave sensors based on well-known open-ended coaxial probes.

Flexible and high sensitive capacitive pressure sensor with microstructured electrode inspired by ginkgo leaf

A reasonable design of flexible pressure sensors is one of the necessary conditions for improving the sensing performance and meeting the demands of various application fields, including intelligent robot, human–machine interface and health monitoring. Herein, the template method is adopted to replicate the unique natural surface microstructure of ginkgo leaf based on the concept of bionics, and a microstructured copper/polydimethylsiloxane electrode is fabricated by the magnetron sputtering method. In addition, a porous carbon black/thermoplastic polyurethane film is used as the intermediate layer to reduce the hysteresis of the sensor. The capacitive pressure sensor exhibits a high sensitivity (1.194 kPa−1, <1 kPa), wide pressure detection range (0–300 kPa), fast response time (80 ms), low hysteresis (maximum to 6.58%), ultra-low detection limit (6.53 Pa), and high stability. Further, we demonstrate the practical applications of the sensor in human joint motion and pulse signal detection, walking state detection, and providing tactile feedback during grasping with hand prosthesis. The experimental results indicate that the proposed capacitive pressure sensor can be potentially applied in the fields of electronic skin, wearable devices, and smart prostheses.

High sensitivity pressure sensor based on a simple SPS fiber loop mirror

High sensitivity pressure sensor based on a simple SPS fiber loop mirror

Highly sensitive pressure and temperature sensors fabricated with poly(3-hexylthiophene-2,5-diyl)-coated elastic carbon foam for bio-signal monitoring

In this report, high sensitivity pressure and temperature sensors are demonstrated based on a single common active material of poly(3-hexylthiophene-2,5-diyl) (P3HT)-coated elastic carbon foam (ECF) for bio-signal monitoring. A conductive microporous elastic foam is obtained via direct carbonization of a commercially available melamine foam at 700 °C and a subsequent dip coating with P3HT. The design incorporating interdigitated electrodes on the bottom of the P3HT-coated ECF is used to fabricate a high-performance pressure sensor with a high pressure sensitivity of 102.4 kPa−1 (<1 kPa), fast response time of 50 ms, and high cyclic durability over 10,000 repetitive pressure loading/unloading cycles. After attachment of the pressure sensor onto the skin, bio-signals such as arterial pulse, swallowing, and voice are distinctively detected. Owing to the thermoelectric property of P3HT, the fabricated temperature sensor shows a high sensitivity of 82.5 μV/K in the range near body temperature between 25 and 55 °C. As a result, distinctive skin temperatures at hand, brow, and neck are measured while attached onto the skin. With an integrated patch of both sensors, the simultaneous detection of critical bio-signals of pulses and skin temperature is accomplished. Furthermore, a dual-mode sensor with a sandwich-type structure enables the detection of pressure by using the thermoelectric voltage generated by the temperature gradient. This work demonstrates a high potential application of our fabricated sensors to skin-attachable wearable devices for bio-signal monitoring.

High sensitive, linear and thermostable pressure sensor utilizing bipolar junction transistor for 5 kPa

Research of pressure sensor chip utilizing novel electrical circuit with bipolar-junction transistor-based (BJT) piezosensitive differential amplifier with negative feedback loop (PDA-NFL) for 5 kPa differential range was done. The significant advantages of developed chip PDA-NFL in the comparative analysis of advanced pressure sensor analogs, which are using the Wheatstone piezoresistive bridge, are clearly shown. The experimental results prove that pressure sensor chip PDA-NFL with 4.0 × 4.0 mm2 chip area has sensitivity S = 11.2 ± 1.8 mV/V/kPa with nonlinearity of 2KNLback = 0.11 ± 0.09%/FS (pressure is applied from the back side of pressure sensor chip) and 2KNLtop = 0.18 ± 0.09%/FS (pressure is applied from the top side of pressure sensor chip). All temperature characteristics have low errors, because the precision elements balance of PDA-NFL electric circuit was used. Additionally, the burst pressure is 80 times higher than the working range.

Pore-scale effects during the transition from capillary- to viscosity-dominated flow dynamics within microfluidic porous-like domains

We perform a numerical and experimental study of immiscible two-phase flows within predominantly 2D transparent PDMS microfluidic domains with disordered pillar-like obstacles, that effectively serve as artificial porous structures. Using a high sensitivity pressure sensor at the flow inlet, we capture experimentally the pressure dynamics under fixed flow rate conditions as the fluid–fluid interface advances within the porous domain, while also monitoring the corresponding phase distribution patterns using optical microscopy. Our experimental study covers 4 orders of magnitude with respect to the injection flow rate and highlights the characteristics of immiscible displacement processes during the transition from the capillarity-controlled interface displacement regime at lower flow rates, where the pores are invaded sequentially in the form of Haines jumps, to the viscosity-dominated regime, where multiple pores are invaded simultaneously. In the capillary regime, we recover a clear correlation between the recorded inlet pressure and the pore-throat diameter invaded by the interface that follows the Young–Laplace equation, while during the transition to the viscous regime such a correlation is no longer evident due to multiple pore-throats being invaded simultaneously (but also due to significant viscous pressure drop along the inlet and outlet channels, that effectively mask capillary effects). The performed experimental study serves for the validation of a robust Level-Set model capable of explicitly tracking interfacial dynamics at sub-pore scale resolutions under identical flow conditions. The numerical model is validated against both well-established theoretical flow models, that account for the effects of viscous and capillary forces on interfacial dynamics, and the experimental results obtained using the developed microfluidic setup over a wide range of capillary numbers. Our results show that the proposed numerical model recovers very well the experimentally observed flow dynamics in terms of phase distribution patterns and inlet pressures, but also the effects of viscous flow on the apparent (i.e. dynamic) contact angles in the vicinity of the pore walls. For the first time in the literature, this work clearly shows that the proposed numerical approach has an undoubtable strong potential to simulate multiphase flow in porous domains over a wide range of Capillary numbers.

Optical Fiber Gas Pressure Sensor Based on Polydimethylsiloxane Microcavity

We experimentally demonstrated a high sensitive gas pressure sensor, which also has more concise processing steps and lower cost. The sensor was fabricated by splicing the single-mode fiber (SMF) and a short section of hollow-core fiber (HCF) which was filled with a Polydimethylsiloxane (PDMS) film to form an enclosed air microcavity with the length of 55 μm. The thin PDMS film also plays a role in reflecting the beam. The thermo-optical effect and the thickness of PDMS film can affect the cavity that is sensitive to external pressure. When the thickness of the PDMS membrane is 3 μm, the measured gas pressure sensitivity reaches to 52.143 nm/Mpa, the linearity is 99.86%, and the cross-sensitivity of the gas pressure over temperature is lower than 2.51 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−3</sup> Mpa/°C. Moreover, the compact structure, high sensitivity, high mechanical strength, and convenient fabrication make it suitable for measuring gas pressure in harsh conditions.

Design of High-sensitivity Hydrostatic Pressure Sensor Based on Brillouin Dynamic Grating

Design of High-sensitivity Hydrostatic Pressure Sensor Based on Brillouin Dynamic Grating

Characterization of Hydroacoustic Optical Fibre Bragg Grating Pressure Sensor Using Different Materials

The Exploration of the ocean with sound waves submarines, object tracking, bed deposits, and ocean communications requires a high sensitive hydroacoustic pressure sensor. Design of highly sensitive hydroacoustic challenges and needs of the present scenario. Proposed work involves the design and development of fiber Bragg grating hydroacoustic pressure sensors for underwater communication. Here side hole package is designed and analyzed in Ansys Multiphysics. Three different coating material is such as the layer of titanium, polyamide, and gold is coated on core fiber of fiber Bragg grating sensor and specific mechanical properties of the layer have been assigned. Centre wavelength and sensitivity of the designed FBG sensor is investigated by applying pressure in the range of 100 MPa to 900 MPa. From the results it is also observed that even for small pressure value sensitivity obtained was considerably high, thus satisfying the requirement of hydroacoustic pressure sensor to detect the low-pressure acoustic signals. The high sensitivity of 4590 nm/RIU obtained for the coating material of polyamide. The result obtained has shown feasibility for the fabrication of FBG for different applications such as underwater acoustic, ocean communication.

A high sensitive graphene piezoresistive MEMS pressure sensor by integration of rod beams in silicon diaphragm for low pressure measurement application

MEMS piezoresistive pressure sensors are most widely explored for various applications such as industrial, automotive and medical field. Each application covers a wide operating range from very low pressure to the higher pressure. In this paper a novel structure is designed by introducing the local stiffness in the diaphragm membrane for low pressure measurement. Rod beams at the diaphragm with combination of graphene piezoresistors, improves overall performance of the pressure sensor in terms of sensitivity. At higher temperature and higher pressure, a noticeable sensitivity is achieved which is compared to the previous design of graphene pressure sensor without rod beam structure. At room temperature (25 °C), sensitivity of pressure sensor with rod beam structure is 6.28 mV/psi. At 30 °C, the sensitivity is 58% higher than sensitivity of pressure sensor without rod beam structure for low-pressure specific range.

Development of high-sensitivity pressure sensor with on-chip differential transistor amplifier

A mathematical model of a high-sensitivity pressure sensor with a novel electrical circuit utilizing a piezosensitive transistor differential amplifier with negative feedback loop is presented. Circuits utilizing differential transistor amplifiers based on vertical n-p-n and lateral p-n-p transistors are analyzed and optimized for sensitivity to pressure and stability of output signal in operating temperature range. Parameters of fabrication process necessary for modeling of I–V characteristics of transistors are discussed. The results of the model are sufficiently close to the experimental data.