High-sensitivity Pressure Sensor Research Articles

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.

High Sensitivity Pressure Sensor Using Tandem Wheatstone Bridge for Low Pressures

High Sensitivity Pressure Sensor Using Tandem Wheatstone Bridge for Low Pressures

Tribo-piezoelectric synergistic BaTiO3/PDMS micropyramidal structure for high-performance energy harvester and high-sensitivity tactile sensing

Triboelectric nanogenerators (TENGs) and piezoelectric nanogenerators (PENGs) represent some of the most promising strategies for converting mechanical deformation and friction into electrical energy. This energy can be used to power electronic devices, such as wearables, and detect mechanical stimuli. Here, we have demonstrated the synergistic integration of piezoelectric and triboelectric effects by incorporating barium titanate (BaTiO3) nanoparticles into a pyramidal polydimethylsiloxane (PDMS) elastomer. This integration aims to enhance the performance of both pressure sensor devices and electrical energy harvesters. The pressure sensitivity of our proposed tribo-piezoelectric device reaches as high as 3.71 V∙kPa−1 for pressure sensing within the range of 0.1–100 kPa, the output voltage increasing to ∼ 370 V at 100 kPa. Our theoretical simulation of electrical power density at this specific pressure reveals that the mechanical deformation of the PDMS elastomer, combined with the polarization of BaTiO3 nanoparticles, synergistically generate tribo-piezoelectric charge on the surface. Therefore, our synergistic combination of triboelectric and piezoelectric effects opens a promising avenue for effectively converting mechanical action into electrical signals. This enables highly efficient energy scavenging and the development of high-sensitivity pressure sensors.

Ultrawide linear range, high sensitivity, and large-area pressure sensor arrays enabled by pneumatic spraying broccoli-like microstructures.

Large-area pressure sensor arrays with a wide linear response range and high sensitivity are beneficial to map the inhomogeneous interface pressure, which is significant in practical applications. Here, we demonstrate a pneumatic spraying method to prepare large-area microstructure films (PSMF) for high performance pressure sensor arrays. The sprayed surface morphology is designable by controlling the spraying parameters. It is worth noting that the constructed "broccoli" like morphology with a swollen top and shrunken bottom inspired a new mechanism to enlarge the linear response range by decreasing the series resistance with pressure increasing. At the same time, the pneumatic sprayed "broccoli" has a rough surface due to droplet stacking, which reduces the initial current effectively. Hence, the sensor achieves a 10 000 kPa ultrawide linear response range with a high sensitivity (98.71 kPa-1), and low detection (5 Pa). The prepared sensor has a small static response error (4.4%) and 5000 cycle full-range dynamic response durability. Finally, the constructed sensor arrays can distinguish the pressure distribution in different ranges clearly, which indicates a great potential in health care, motion detection, and the tire industry.

Lumen Pressure Modulation in Chicken Embryos.

Pressure exerted by fluid contained within a lumen plays a crucial role in the growth, morphogenesis, and patterning of epithelial organs. Accurate modulation of lumen pressure in the developing embryo requires sensitive and robust methods that can detect and vary pressure in the range of tens to hundreds of Pascals (Pa). Here we describe a simple, cost-effective protocol for setting up a pressure modulation apparatus combining a high-sensitivity pressure sensor and a water column whose height can be finely tuned. We demonstrate lumen pressure control using the developing brain of early chicken embryos.

(Invited) Fabriations and Applications Using Liquid Metal Towards Stretchable Electronics

Highly deformable devices have many potential applications, including wearable electronics, robotics and health monitoring. Mechanically deformable devices and sensors can conformally cover electronic systems on curved or soft surfaces. Liquids deform more easily than solids, so sensors and actuators that utilise liquids trapped in soft templates as sensing components are ideal platforms for such applications. Such highly deformable electronics using ultra-flexible conductive materials are called stretchable electronics. Liquid metals (LMs) are one of the leading materials. In the last few years, liquid metals have steadily gained interest, especially in the field of flexible soft electronics and related applications. The term liquid metal has several definitions and many research efforts are underway to utilise liquid metals in various fields. The simplest definition can be given as 'a composite of low-melting alloys that retain their liquid state at room temperature, are easily deformable and have high electrical conductivity'. Here, an overview of liquid metals, new processing methods, sensors and actuators, batteries and smart devices are reported in focus.To date, we have adopted a patterned method using microfluidic channels with regard to processing methods for liquid metals such as EGaIn and Galinstan. Microfluidic channels are one of the most accurate and reliable method of producing electrode patterns among the three processing methods, although they are limited by the substrate material and pattern design for pattern fabrication. The creation of microfluidic channels follows the method used in Micro Electro Mechanical Systems (MEMS) and micro Total Analysis Systems (microTAS). In practice, the molds are fabricated by photolithography using SU-8 photoresist. Rubber materials such as polydimethylsiloxane (PDMS) are poured into the mold and allowed to cure. Microfluidic channels are fabricated by chemically bonding the flat PDMS with the PDMS to which the pattern has been transferred. We have succeeded in fabricating a two-dimensional pattern of liquid metal by the method described above. Furthermore, we have successfully fabricated microfluidic channels by 3D printing of rubber materials and constructed 3D circuits by using liquid metal. As liquid metal is a liquid material, processing methods centred on "printing" processing can be used, and the most suitable processing method can be selected according to the device and application.Physical sensors such as strain sensors and chemical sensors such as oxygen gas sensors have been reported using liquid metal wiring. By optimising the wiring of the liquid metal, capacitor structures and resistors can be fabricated. By encapsulating these in a flexible material, PDMS, it is possible to realize sensors that can measure displacements such as strain. Indeed, by optimising three sensor structures, we have reported a physical sensor capable of sensing three sensing modes: two-dimensional tension and vertical compression. However, taking into account the actual application in wearable devices for healthcare applications such as pulse rate, a detection sensitivity below 1 k Pa is required. The authors realized a high-sensitivity pressure sensor by using a Wheatstone bridge circuit structure for the liquid metal wiring in the PDMS to form a Diaphragm sensor. In fact, a pulse rate sensing device was realized based on the developed device. Furthermore, a PDMS glove capable of measuring 16 points simultaneously was realized by attaching the developed pressure sensor to a hand mold using 3D printing5).Such physical sensors are very easy to construct and can be realized with one type of liquid metal. While there are many different types of liquid metals as described above, liquid metals easily mix when they come into contact with each other. Therefore, the authors proposed a "liquid" state heterojunction using ionic liquids and liquid metals with extremely low vapor pressure. By using ionic liquids [EMIM][Otf], [EMIM][PF6] and [EMPYR][NTf2], sensors for temperature, humidity and oxygen gas were realized. Furthermore, with regard to their sensitivity, the detection sensitivity was 10 times higher than that of normal metal temperature and humidity sensors for temperature and humidity sensors. In this study, heterojunctions were realized using microfluidics. Due to the low Reynolds number of the microfluidics, the robustness of the liquid state heterojunction with respect to deformation was also very high due to the high viscosity effect, making the configuration suitable for stretchable sensors. In addition to electrodes and sensors, development of batteries and smart devices has also been initiated and will be reported in this presentation.

Sandpaper-assisted preparation of microstructured multifunctional PANI/PVA composite hydrogel film for high-sensitivity pressure sensors with accurate pressure identification and motion monitoring

Bio-inspired microstructure surface flexible piezoresistive sensors offer an attractive opportunity for a variety of wearable device applications. Unfortunately, the realization of high-performance piezoresistive sensors still faces great challenges owing to the balance between responsitivity and sensing capability of them, as well as being limited by the level of deformation of their surface structures. Here, we propose a simple and efficient, low-cost sandpaper-assisted solution casting-scraping strategy to fabricate PANI/PVA hydrogel film with the reverse random height distribution (RHD) spinosum microstructure on the surface that is simultaneously conductive, flame retardant, and EMI shielding. The flexible piezoresistive sensor designed based on this film can detect pressure from 0.01 N to 20 N with a responsitivity of 77.7263 kPa−1 in the region of 0.03183–1.27324 kPa, a quick response/recovery delay of 18 ms/30 ms, and a good reliability within 2000 load-unload cycles. Notably, this piezoresistive sensor can accurately identify objects of different masses and monitor physiological signals of human motion, and can also produce significant current responses to extremely slight mouse clicks and handwriting styles. The successful preparation of multifunctional PANI/PVA microstructured film provides a new idea to explore the potential applications of piezoresistive sensors in flexible wearable electronic devices.

Porous Conductive Hybrid Composite with Superior Pressure Sensitivity and Dynamic Range

AbstractPorous conductive composites hold immense promise in flexible sensors and soft robotics due to their pressure‐responsive electrical conductivity. Unlike non‐porous composites whose pressure sensitivity is limited by relatively high elastic modulus, porous materials show improved pressure sensitivity owing to their lower stiffness. Despite this, existing porous composites still suffer from insufficient pressure sensitivity or narrow detection ranges, severely restricting their applications. This work presents a liquid metal hybrid filler porous composite to address these issues. Through experiment and simulation optimization, the composite exhibits a conductivity increase of five order‐of‐magnitude over 0–250 kPa, demonstrating a 900% higher pressure sensitivity than the best non‐porous counterpart in this work. The composite maintains a highly linear response (R2 of 0.999) over an exceptionally wide dynamic range up to 8.9 MPa, with a pressure sensitivity of 8.1 MPa–1, surpassing the state‐of‐the‐art in both pressure range and sensitivity. A proof‐of‐concept pressure sensor array further demonstrates the composite's excellent sensing performance, showing stable response under 100‐cycle loading with a measured pressure deviation of only 1.4%, outperforming existing commercial pressure sensors in terms of sensitivity, detection range and cyclic stability. The porous material design strategy opens doors for high sensitivity pressure sensors in wearable devices, flexible electronics, and soft robotics.

All-Nanochitin-Derived, Super-Compressible, Elastic, and Robust Carbon Honeycombs and Their Pressure-Sensing Properties over an Ultrawide Temperature Range.

Elastic carbon aerogels show great potential for various applications but are often hindered by structure-derived fatigue failure, weak elasticity with low compressibility, and low stress and height retention. Herein, we demonstrate a super-elastic and fatigue-resistant nanochitin-derived carbon honeycomb with honeycomb-like anisotropic microstructures and carbon-based molecular structures, which was tailored by optimizing the nanochitin concentrations and carbonization temperatures. The carbon honeycomb fabricated at a nanochitin concentration of 1.0 wt % and a carbonization temperature of 900 °C demonstrated anisotropic honeycomb channels, nanofibrous network channel walls with few cracks, and weak interactions between the carbonized nanochitin, which afforded high compressibility with up to 90% strain and complete recovery. In particular, the carbon honeycomb provided good fatigue resistance with high stress and height retentions of 87 and 94%, respectively, after more than 10,000 compression cycles at 90% strain. Moreover, the tailored anisotropic honeycomb channels and molecular structures endowed the carbon honeycomb with elasticity even under severe conditions, such as exposure to flame (approximately 1000 °C) and liquid nitrogen (approximately -196 °C). Owing to these properties, the nanochitin-derived carbon honeycomb could act as a high-sensitivity pressure sensor for a wide working pressure range of 0-185.5 kPa and ultrawide temperature range of -196-600 °C. This study can provide a promising route to develop all-biomass-derived, super-elastic, and fatigue-resistant carbon materials for pressure sensing under harsh conditions and for versatile electronic applications.

Ultrafast and facile construction of programmable, multidimensional wrinkled-patterned polyacrylamide/sodium alginate hydrogels for human skin-like tactile perception

Customizable structures and patterns are becoming powerful tools for biomimetic design and application of soft materials. The construction of long-range ordered self-wrinkled structures on multi-dimensional and complex-shaped surfaces with facile, fast and efficient strategies still faces serious challenges. During the stretch-recovery process, the carboxyl groups in the polyacrylamide/sodium alginate dual network gel form robust coordination with Fe3+ to achieve a hard shell layer, resulting in a modulus mismatch between the inner soft layer and the outer hard layer, thereby forming a wrinkled surface. This flexible strategy allows simultaneous construction of complex topologies from 1D to 3D wits well-organized microstructure and controllable dimensions. The mechanism of the influence of ion treating time and pre-stretching ratio on wrinkle wavelength was explored in detail. The finite element simulations matched well with the experimental results. Due to the unique surface and dual crosslinking network, the self-wrinkled hydrogel maintains a high sensitivity of up to 67.47 kPa−1 in 1000 compression cycles. As a high-sensitivity pressure sensor integrated into the detection system, it can be efficiently applied to the contact dynamic tactile perception and monitoring of various movement behaviors of the human body.

A flexible and highly sensitive capacitive pressure sensor with fast response based on a hierarchically micro-structured PDMS dielectric layer

Flexible high-sensitivity pressure sensors have seen rapid growth in the last few years in applications like electronic skin, smart wearables and medical health monitoring. In this work, we develop a high-flexibility capacitive pressure sensor design based on a hierarchical, micro-pyramid-structured dielectric layer of polydimethanes. The goal of this design is to achieve low-hysteresis capacitive pressure sensors with increased sensitivity and reduced response time. To optimize the performance of the proposed pressure sensor, we designed and fabricated several different micro-pyramid structures on the silicon template using standard photolithography and anisotropic etching. As a result, the pressure sensor with a hierarchical micro-pyramid structure achieved through graphic transfer has the best performance, with a sensitivity of up to 2.64 kPa−1 (0–2 kPa), a response time of 45 ms, a low limit of detection of < 8 Pa, and high stability over at least 1200 loading cycles. As a result of these remarkable performance features, the pressure sensor proposed can be effectively utilized for the detection of physiological signals as well as mechanical pressure which can be widely used in the fields of motion sensing, health monitoring and intelligent robots.

High-Sensitivity Pressure Sensors Using PPy/MWCNTs/PDMS@Melamine Foam for Human Motion Detection on Land and Underwater

High-Sensitivity Pressure Sensors Using PPy/MWCNTs/PDMS@Melamine Foam for Human Motion Detection on Land and Underwater

Highly Sensitive and Flexible Capacitive Pressure Sensors Based on Vertical Graphene and Micro-Pyramidal Dielectric Layer.

Many practical applications require flexible high-sensitivity pressure sensors. However, such sensors are difficult to achieve using conventional materials. Engineering the morphology of the electrodes and the topography of the dielectrics has been demonstrated to be effective in boosting the sensing performance of capacitive pressure sensors. In this study, a flexible capacitive pressure sensor with high sensitivity was fabricated by using three-dimensional vertical graphene (VG) as the electrode and micro-pyramidal polydimethylsiloxane (PDMS) as the dielectric layer. The engineering of the VG morphology, size, and interval of the micro-pyramids in the PDMS dielectric layer significantly boosted the sensor sensitivity. As a result, the sensors demonstrated an exceptional sensitivity of up to 6.04 kPa-1 in the pressure range of 0-1 kPa, and 0.69 kPa-1 under 1-10 kPa. Finite element analysis revealed that the micro-pyramid structure in the dielectric layer generated a significant deformation effect under pressure, thereby ameliorating the sensing properties. Finally, the sensor was used to monitor finger joint movement, knee motion, facial expression, and pressure distribution. The results indicate that the sensor exhibits great potential in various applications, including human motion detection and human-machine interaction.

A 2D photonic crystal indium arsenide based with dual micro-cavities coupled to a waveguide as a platform for a high sensitivity pressure sensor

A 2D photonic crystal indium arsenide based with dual micro-cavities coupled to a waveguide as a platform for a high sensitivity pressure sensor

Large Range and High-Sensitivity Pressure Sensor Based on Integrated Mach-Zehnder Interference

Large Range and High-Sensitivity Pressure Sensor Based on Integrated Mach-Zehnder Interference

Rational designed microstructure pressure sensors with highly sensitive and wide detection range performance

• High sensitivity (26.55 kPa −1 ) and wide work range (0.9 Pa-140 kPa) pressure sensor was demonstrated. • Micro-nano hierarchical structure sponge surface with random uneven pattern. • PDMS sponge fabricated via mixed sacrifice template and electrostatic self-assembly methods. • The pressure sensor has great potential for healthcare and human-machine interfaces. Highly sensitive pressure sensors are often deployed in human-machine interaction area, touch screen and human motion detection. However, there are still great challenges to fabricating with high sensitivity pressure sensor with wide-range detection. Herein, we developed a new strategy to fabricate a highly sensitive pressure sensor using sandpaper and improve its detection range using a sacrificial template. It was the fthatirst time to combine microstructure processing with the sacrificial template method to fabricate pressure sensor. The microstructure of sandpaper endowed the sensor with high sensitivity, and the elastic substrate enhanced the sensor ability to resist high pressure without being damaged. The fabricated sensor device exhibits a superior sensitivity of 39.077 kPa −1 in the range from 50 kPa to 110 kPa with a broad linear response. Remarkably, high pressure ceiling (<160 kPa) ensures that the sponge could be applied in different practical conditions to monitor a range of subtle human motions including finger, wrist bending, and pulse. For applications, the sensor device can not only detect the foot stepping behavior (0.7 MPa) but also produce an obvious response to an extremely slight paper (9 mg, ∼0.9 Pa). The successful preparation of this micro-structured elastic sponge material provided new ideas for exploring its potential applications in pressure sensors and flexible wearable electronic devices.

Silver Nanoflakes-Enhanced Anisotropic Hybrid Composites for Integratable Pressure Sensors.

Flexible pressure sensors based on polymer elastomers filled with conductive fillers show great advantages in their applications in flexible electronic devices. However, integratable high-sensitivity pressure sensors remain understudied. This work improves the conductivity and sensitivity of PDMS-Fe/Ni piezoresistive composites by introducing silver flakes and magnetic-assisted alignment techniques. As secondary fillers, silver flakes with high aspect ratios enhance the conductive percolation network in composites. Meanwhile, a magnetic field aligns ferromagnetic particles to further improve the conductivity and sensitivity of composites. The resistivity of the composite decreases sharply by 1000 times within a tiny compression strain of 1%, indicating excellent sensing performance. On the basis of this, we demonstrate an integratable miniature pressure sensor with a small size (2 × 2 × 1 mm), high sensitivity (0.966 kPa-1), and wide sensing range (200 kPa). Finally, we develop a flexible E-skin system with 5 × 5 integratable sensor units to detect pressure distribution, which shows rapid real-time response, high resolution, and high sensitivity.

High-sensitive MEMS Fabry-Perot pressure sensor employing an internal-external cavity Vernier effect.

In this paper, a high sensitivity pressure sensor employing an internal-external cavity Vernier effect is innovatively achieved with the microelectromechanical systems (MEMS) Fabry-Perot (FP) interferometer. The sensor consists of silicon cavity, vacuum cavity, and silicon-vacuum hybrid cavity, which is fabricated by direct bonding a silicon diaphragm with an etched cylindrical cavity and a silicon substrate. By rationally designing the optical lengths of the silicon cavity and silicon-vacuum hybrid cavity to match, the internal-external cavity Vernier effect will be generated. The proposed cascaded MEMS FP structure exhibits a pressure sensitivity of -1.028 nm/kPa by tracking the envelope evolution of the reflection spectrum, which is 58 times that of the silicon-vacuum hybrid cavity. What's more, it owns a minimal temperature sensitivity of 0.041 nm/°C for the envelope spectrum. The MEMS FP sensor based on internal-external cavity Vernier effect as the promising candidate provides an essential guideline for high sensitivity pressure measurement under the characteristic of short FP sensing cavity length, which demonstrates the value to the research community.

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.