Stable Pressure Sensor Research Articles

All-Polydimethylsiloxane-Based Highly Flexible and Stable Capacitive Pressure Sensors with Engineered Interfaces for Conformable Electronic Skin.

Rapid development of flexible pressure sensors is indispensable in electronic skin to have the sensing capability to static and dynamic pressures. Besides high sensitivity and low hysteresis, the high flexibility and stability of these sensors are of paramount importance owing to the application requirement of conformable pressure mapping and rugged structure. Here, we describe a novel approach for highly flexible capacitive pressure sensors with engineered stable interfaces employing PDMS-based substrates and a micropyramidal dielectric layer, Au electrodes, and molecular adhesive. The sensor/matrix stack consists of five interfaces with strong interfacial adhesion achieved using MPTMS molecular adhesive and a partially cured PDMS lamination layer. A highly flexible capacitive pressure sensor capable of a wide pressure sensing range (up to 550 kPa) is developed with a high sensitivity (46.6 MPa-1 in ≤1 kPa), capability to sense pressure as low as 27 Pa, low hysteresis (4.05%), and high stability for large pressures (11,400 cycles @ 250 kPa). The sensor is successfully demonstrated for arterial pulse signal acquisition and performing a press task when attached on the forefinger. A flexible pressure sensor matrix of 4 × 4 pixels is developed. It can be flexed or crumpled; hence, it is conformably attached on a planar surface and a non-planar 3D-printed surface for single-point and multipoint pressure sensing. The sensor exhibited a maximum shear strain of 2.27 N before breakage. These highly flexible pressure sensor and matrix are also compared with a semi-flexible IO-PET electrode-based pressure sensor and matrix to clearly bring out the flexibility and stability advantages. The proposed process is simple and scalable and offers a conformably stable pressure sensor matrix for electronic skin development.

A dual-module co-regulated stable pressure sensor for human activity monitoring.

Flexible pressure sensors have received significant attention for applications in wearable devices and human health monitoring in healthcare. Nevertheless, the preparation of pressure sensors with a wide operating range and high sensitivity remains a huge challenge. Herein, a piezoresistive sensor with a porous microstructure is prepared by using a sandpaper and salt dual-template method. Carbon black and carbon nanotubes are used as conductive fillers and the pressure sensor shows a high sensitivity (58.33 kPa-1) and extremely fast response and recovery times (3 and 10 ms, respectively). Furthermore, this CNT/PDMS/CB sensor shows a high detection limit of 400 kPa and excellent cycling stability of over 20 000 cycles. This high-performance pressure sensor is promising for many applications such as wearable electronics and health monitoring.

A Flexible, Highly Accurate, and Stable Pressure Sensor with Anti‐Interference from Temperature, Sweat, and Humidity

AbstractThe highly accurate and stable pressure sensors with anti‐interference from varying sensing environments (temperature and humidity) are essential and a challenge in practical applications. However, real‐time electrical resistance fluctuation or even sensing inaccuracy are widely existed due to the sensibility of conductive materials towards varying temperatures, humidity, and sweat circumstance. Here, for the first time, the hydrophobic, non‐fluoride, titanium dioxide nanoparticle (TiO2‐ODI) modified carbon nanotube (CNT)/carbon black (CB) pressure sensors are introduced to achieve anti‐interference from temperature, droplets, and humidity. The sensors with a near‐zero temperature coefficient of resistance (near‐ZTC) effect (≈ −10 to 70 °C). The anti‐interference from moisture benefits from the effective isolation effect of the hydrophobic TiO2‐ODI layer. Meanwhile, the TiO2‐ODI/CNT/CB pressure sensors obtain a favorable sensitivity of 1.57 kPa−1, a fast response time of 20 ms, a negligible hysteresis ratio of 1.9%, prominent air permeability, and a facile scalable strategy. Hence, the TiO2‐ODI/CNT/CB pressure sensors are feasible for accurately and stably sensing under varying sensing environments by efficiently suppressing interferences from varying temperatures, high humidity, and sweat.

Ultrasensitive and stable pressure sensor based on tapered optical fibres

Micro/nanofibres have been emerging as an interdisciplinary platform for exploring novel sensing technology on the micro/nanoscale. This work proposes and demonstrates an ultrasensitive and stable pressure sensor based on the perturbation of adiabatic conditions during the optical mode evolving in the transition region. In our experiment, when attached to a glass slide, the sensor shows ultrahigh pressure sensitivity of 1.52 kPa−1 which is about three times the sensitivity of the waist region. Simultaneously, the sensing region of the fibre has a diameter of tens of microns to provide a better mechanical structure strength. These preliminary results demonstrate that the sensor has the advantages of stable structure, high sensitivity, and simple preparation process, which may have potential in practical applications.

Alcohol-based highly conductive polymer for conformal nanocoatings on hydrophobic surfaces toward a highly sensitive and stable pressure sensor

Conformal and ultrathin coating of highly conductive PEDOT:PSS on hydrophobic uneven surfaces is essential for resistive-based pressure sensor applications. For this purpose, a water-based poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) solution was successfully exchanged to an organic solvent-based PEDOT:PSS solution without any aggregation or reduction in conductivity using the ultrafiltration method. Among various solvents, the ethanol (EtOH) solvent-exchanged PEDOT:PSS solution exhibited a contact angle of 34.67°, which is much lower than the value of 96.94° for the water-based PEDOT:PSS solution. The optimized EtOH-based PEDOT:PSS solution exhibited conformal and uniform coating, with ultrathin nanocoated films obtained on a hydrophobic pyramid polydimethylsiloxane (PDMS) surface. The fabricated pressure sensor showed high performances, such as high sensitivity (−21 kPa−1 in the low pressure regime up to 100 Pa), mechanical stability (over 10,000 cycles without any failure or cracks) and a fast response time (90 ms). Finally, the proposed pressure sensor was successfully demonstrated as a human blood pulse rate sensor and a spatial pressure sensor array for practical applications. The solvent exchange process using ultrafiltration for these applications can be utilized as a universal technique for improving the coating property (wettability) of conducting polymers as well as various other materials.

Low-cost, highly sensitive and stable pressure sensor based on glass fiber surfacing mat coated with graphene

High-performance pressure sensors have caused widespread concern due to the potential applications in 3D-touch technology and wearable electronic devices. Herein, a new type of graphene pressure sensor based on the glass fiber surfacing mat coated with graphene oxide aqueous solution by a spray-vacuum filtration method and HI acid reduction method is reported. It is a simple and highly effective method to reduce graphene oxide films into highly conductive graphene films without destroying their integrity and flexibility at a low temperature based on the nucleophilic substitution reaction. The FTIR, SEM and conductivity tests indicate that the optimum time for graphene oxide to be reduced is 30[Formula: see text]min, under this condition enter the epoxy group has been reacted without damaging the regular sp2 hybrid C atom structure in graphene. The conductivity of the graphene pressure sensor is increased significantly to 23260[Formula: see text]S/m. The monotonic compressing test for 100[Formula: see text]Pa/s and the test of the metal block placement and removal demonstrate that the sensor exhibits relatively high linearity of 99.74% between the response and pressure, the advantage makes the sensor monitor pressure more accurately. More importantly, the pressure sensor based on the glass fiber surfacing mat coated with graphene shows extremely high sensitivity (0.169[Formula: see text][Formula: see text]), fast response time (251[Formula: see text]ms) and good stability for 1000 cycles. Based on its superior performance, it also demonstrates potential applications in measuring pressure and human body’s motions.

Highly stable pressure sensor based on carbonized melamine sponge using fully wrapped conductive path for flexible electronic skin

Abstract High-performance stretchable and wearable electronic skins (e-skins) with high sensitivity and large sensing range are urgently required with the rapid development of internet of things and artificial intelligence. Herein, a simple and efficient “dip coating” method was proposed for preparing flexible pressure sensors based on the combination of silicone rubber (SR) and carbonized melamine sponge (CMS). From the as-prepared flexible sensor, good stability, mechanical performances, anti-interference ability, wide working range (0–550 kPa), fast response (~120 ms), frequency-dependent performance, reliable repeatability (~10000 cycle) and stable signal waveform output can be readily obtained. This CMS-based flexible pressure sensor can not only detect human motion (finger bending, knee squatting-arising and plantar pressure changing) in real time and reliably, but also detect the pressure distribution in space through arraying. The experimental results demonstrate that the flexible pressure sensor based on functional-sponge can be a promising candidate for healthcare monitoring and wearable electronics in artificial intelligence.

Simple and efficient pressure sensor based on PDMS wrapped CNT arrays

Pressure sensors are critical components in the development of electronic skin for broad applications in healthcare monitoring and clinical diagnosis. Producing an inexpensive, sensitive, stable pressure sensor, however, remains a long-term work in progress. Here, we designed and fabricated a simple but efficient pressure sensor based on PDMS wrapped free standing CNT arrays. In contrast to regular conductive films made by dispersed nanomaterials, CNT arrays are naturally crooked and interconnected with numerous tunable contact points, resulting in a highly sensitive and stretchable sensor. The pressure sensor also exhibits rapid response and recovery times of less than 26 and 57 ms, respectively. Even after 8000 test cycles, the amplitude of the current change shows no observable fluctuations, demonstrating the sensor's strong reliability. With its high flexibility and low weight, the pressure sensor can be comfortably attached to the skin for monitoring critical physiological measurements such as radial artery pressure and respiratory rate. Furthermore, this work provides a new option to design various device by using carbon-based materials without the problem of stacking.

New pressure sensing elements for FFR coronary catheter

The next generation FFR Coronary Catheter includes a new stable pressure sensor, AD conversion at the tip of the catheter and mount of these components on the sidewall of the catheter instead of the guide wire enabling thus to use standard guide wires. The new ultrathin capacitive MEMS pressure sensor die with corresponding readout ASIC circuit offers better accuracy, robustness and automated assembly. The measured performance values of the fabricated chips correlate well with the simulated ones indicating comprehensive understanding of the sensor operation and control of the fabrication process. The test measurements outperformed the specifications for the FFR pressure sensing.

New Developments and Applications of Coal Mine Pressure and Force Monitoring Technology

Some new techniques used to improve the characteristics of vibrating-wire sensor and their applications in coal mine pressure and force monitoring are summarized. First, the new mathematical model and its applications are given. Second, the match of wire and diaphragm for the horizontal wire type sensor to reduce the hysteretic of the sensor is presented. Third, the weak excitation of the wire is stated which can effectively solve the problem of frequency variations. At last, the techniques of piston-conveying pressure and force conversion can be used to improve the accuracy and long-term stability, and to design the wide range、 high accuracy、high resolution and long-term stable pressure sensors and force sensors.

An Accurate and Stable Pressure Sensor for Constant-Level Balloon Experiments from the Boundary Layer to the 10 kPa Level

This paper describes a sensor that answers to a need of accuracy, stability and low cost for constant-level balloon experiments. The same type of sensor can be employed for any level up to 10 kPa (100 mb) and we hope for an extension up to 1 kPa (10 mb). We review more particularly the aging, temperature effect and air safety tests for the 20 kPa (200 mb) sensor, concluding that 5 × 10−2 kPa (0.5 mb) accuracy is obtained over a six-month period with an instrument that complies with air safety standards.