An ultra-sensitive resistive pressure sensor based on hollow-sphere microstructure induced elasticity in conducting polymer film

Wearable sensors are increasingly used in a wide range of applications such as tactile sensors and artificial skins for soft robotics, monitoring human motions for wellbeing and sports performance, and pressure control of compression garments for wound healing. In this work, an ultrasensitive resistive pressure sensor based on conductive polydimethylsiloxane (PDMS) thin films with different microstructures is presented. These microscopic features include micropyramids, micro‐semispheres, and micro‐semicylinders which are created by soft lithography replication of 3D printing templates. To enable piezoresistivity, a thin layer of carbon nanofibers (CNFs) is spray‐coated on the textured PDMS film. The resistance changes of the three microstructure designs under compression loading show that the micro‐semicylinder‐based sensor has the highest sensitivity of −3.6 kPa−1. Finite element modeling reveals that among the three designs, the micro‐semicylinders show the largest change in contact area under the same pressure, consistent with the experimental results that the largest resistance change under the same pressure. This sensor is capable of detecting pressure as low as 1.0 Pa. This 3D printing technology is a promising fabrication technique to design microstructured piezoresistive layers, paving the way to tailor sensor performance by engineering their microstructures and to produce ultrasensitive pressure sensors at low cost.

Wearable pressure sensors with ultrahigh sensitivity and flexibility have garnered tremendous attention because of their abilities to mimic the human somatosensory system and perceive surrounding pressure distribution. Herein, an ultrasensitive pressure sensor was fabricated with surface-patterned nanofibrous membranes (SPNMs) via a facile replica method from available plain-weaved nylon textiles. The SPNMs were composed of internal three-dimensional interpenetrating polyolefin elastomer nanofibers and silver nanowires (Ag NWs). The effects of the geometry of surface patterns and the density of the Ag NW network on the sensing performance of the assembled pressure sensor were systematically investigated. The results indicated that clavate groove-shaped surface patterns improved the sensitivity and a larger groove spacing contributed to higher sensitivities, whereas denser Ag NWs would reduce the sensing performance. The optimal pressure sensor assembled with SPNMs-45 and a Ag NW fraction of 3.8% showed high sensitivity (19.4 kPa-1) below the pressure of 2.76 kPa, a low detection limit (<1.6 Pa), fast response (30 and 42 ms), as well as excellent durability. These outstanding performances demonstrated its promising potential for wearable electronic applications, like detecting the spatial pressure distribution and monitoring human muscle motions.

We demonstrate a flexible, ultra-sensitive resistive pressure sensor based on the foam-like structure of laser-scribed graphene (LSG). Benefitting from the unique microstructure of the LSG, the sensitivity of the pressure sensor is as high as 0.96 kPa−1 in the low pressure range (0∼50 kPa), which is the highest among all reported graphene-based pressure sensors. Moreover, the sensitivity in the high pressure range (50∼113 kPa) is 0.005 kPa−1. The response of the pressure sensor is highly stable up to 100 cycles with excellent performance. Our pressure sensor can meet the needs of specific applications, for example, high sensitivity for low-pressure applications and low sensitivity for high deformation applications. Moreover, the laser-scribing technology could enable large-scale production of the LSG pressure sensor with low cost in ∼20 minutes. Our work indicates that laser scribed flexible graphene pressure sensors could be widely used for artificial electronic skin (e-skin), medical-sensing, bio-sensing and many other areas.

Flexible pressure sensors play an important role in electronic skins (E-Skins), which mimic the mechanical forces sensing properties of human skin. A rational design for a pressure sensor with adjustable characteristics is in high demand for different application scenarios. Here, we present tunable, ultrasensitive, and flexible pressure sensors based on compressible wrinkled microstructures. Modifying the morphology of polydimethylsiloxane (PDMS) microstructure enables the device to obtain different sensitivities and pressure ranges for different requirements. Furthermore, by intentionally introducing hollow structures in the PDMS wrinkles, our pressure sensor exhibits an ultrahigh sensitivity of 14.268 kPa-1. The elastic microstructure-based capacitive sensor also possesses a very low detectable pressure limit (1.5 Pa), a fast response time (<50 ms), a wide pressure range, and excellent cycling stability. Implementing respiratory monitoring and vocalization recognition is realized by attaching the flexible pressure sensor onto the chest and throat, respectively, showing its great application potential for disease diagnosis, monitoring, and other advanced clinical/biological wearable technologies.

Flexible pressure sensors that mimic human skin are attractive for electronic skin, soft robotics, and healthcare, but it remains difficult to combine ultrahigh sensitivity, wide range, and long-term stability in one device. Here, we present an ultra-sensitive iontronic pressure sensor (USIPS) based on a fingerprint-inspired spiral interpolating electrode, a laser-processed spacer, and a thermoplastic polyurethane (TPU)/graphene/multi-walled carbon nanotube (MWCNT)/ionic-liquid composite layer microstructured into cylindrical protrusions by femtosecond-laser engraving. This architecture amplifies contact mechanics and electric-double-layer modulation, delivering ultrahigh sensitivities of ∼1.92 × 105 kPa-1 (0-110 kPa), ∼6.58 × 104 kPa-1 (110-300 kPa), and ∼1.91 × 104 kPa-1 (300-900 kPa), together with a wide detection range (from ∼577 Pa to 900 kPa), fast response (∼20 ms), and excellent stability under prolonged high-pressure loading. Coupled with a tailored signal-processing and machine-learning pipeline, the USIPS enables quantitative hardness/softness perception and accurate discrimination of representative materials, while also supporting pulse monitoring, robotic grasping, and plantar gait analysis. These results demonstrate a unified iontronic-AI platform for wide-range, high-fidelity tactile sensing and intelligent perception.

Ultra-sensitive air pressure sensor based on gelatin diaphragm-based Fabry-Peroy interferometers and Vernier effect

Ultrasensitive resistive pressure sensors are developed by using an additive manufacturing technique (3D printing) to create contacting surfaces with different microstructure features. These new sensors' performance is highly tunable by adjusting the surface topographic features. More details can be found in article number 1800403 by Shuhua Peng, Chun H. Wang, and co-workers.

Ultrasensitive and flexible pressure sensors that can perceive and respond to environmental stimuli have attracted considerable attention due to their potential applications in wearable electronics and electronic skin devices. Here, we report a simple and low-cost strategy to fabricate high-performance pressure sensors via constructing a unique conductive/insulating/conductive sandwich-like porous structure (SPS). Interpenetration of the conductive graphene network throughout the porous insulating interlayer produces a highly efficient transition from the non-conductive to the conductive state. Consequently, the SPS sensors exhibit an extreme resistance-switching behavior (resistance change of >105 at 30 kPa), high sensitivity (∼0.67 kPa-1, <1.5 kPa), fast response/recovery time (∼10 and ∼16 ms) and outstanding mechanical stability. Such SPS pressure sensors are applicable for detecting various mechanical deformation modes (press, bend and torsion) and different stress/strain levels (from gait feature, finger/wrist/elbow movement to breathing monitoring and real-time pulse wave), providing a new concept of device design for wearable electronic applications.

Flexible pressure sensors with high sensitivity and wide pressure response range are attracting considerable research interest for their potential applications as e-skins. Nowadays, it seems a dilemma to realize high-performance, multifunctional pressure sensors with cost-effective, scalable strategy, which can simplify wearable sensing systems without additional signal processing, enabling device miniaturization and low power consumption. Herein, pressure sensors with ultrahigh sensitivity and broad response pressure range are developed with a low-cost, facile method by combining strain-induced percolation behavior and contact area contributions. Due to their special surface structure and strain induced conductive network formation behavior, these unique pressure sensors exhibit wide sensing range of 1 Pa-500 kPa, ultra-high sensitivity (1×106 kPa-1and 3.1×104 kPa-1 in the pressure ranges of 1 Pa-20 kPa and 20-500 kPa, respectively), fast signal response (< 50 ms), low detect limit (1 Pa) and high stability over 500 loading/unloading cycles. These characteristics allow the devices work as e-skins to monitor human pulse signals and finger touch. Moreover, these sensors illustrate precise electrical response to mechanical vibration, bending and temperature stimuli, which afford the ability of detecting cell phone call-in vibration signals, joint bending and spatial pressure & temperature distributions, indicating promising applications in next-generation wearable, multifunctional e-skins.

Polyurethane sponges-based ultrasensitive pressure sensor via bioinspired microstructure generated by pre-strain strategy

Ultrasensitive and stable pressure sensor based on tapered optical fibres

An ultra-sensitive gas pressure sensor based on tapered fiber coated with PDMS film working at TAP

Starfish-inspired ultrasensitive piezoresistive pressure sensor with an ultra-wide detection range for healthcare and intelligent production

The growing demand for next-generation wearable technologies characterized by high sensitivity, low detection limits, and a broad pressure range drives the need for advanced pressure sensors capable of detecting subtle physiological signals and large-scale mechanical inputs for ergonomic applications. Here, we present an ultrasensitive ionotronic pressure sensor (IPS) based on a cobalt-rich zeolitic imidazolate framework (ZIF-67)-grown, highly porous ionic nanofibrous membrane (INM) as a dielectric separator, paired with a hybrid nanoporous carbon-incorporated laser-induced graphene (HNPC@LIG) and ionic PVDF-HFP@IL as the electrode/electrolyte layer. The ZIF-67-incorporated INM lowers the baseline capacitance and enhances ion transport under pressure, enabling efficient electric double layer (EDL) formation, while the HNPC@LIG offers a high surface area. As a result, the IPS achieves an exceptionally wide, linear detection range (0-1000 kPa) and high sensitivity: 5073 kPa-1 (0-140 kPa), 18,366 kPa-1 (140-300 kPa), 5324 kPa-1 (300-470 kPa), and 1023 kPa-1 (470-1000 kPa). This performance surpasses that of current state-of-the-art sensors, enabling precise detection of lip motion, respiration, pulse, and posture, paving the way for physiological signal and posture monitoring for ergonomic assistance.

The rise of Internet of Things and wearable healthcare electronics has prompted the rapid development of wearable pressure sensors. A novel developing trend focuses on a pressure sensor with high sensitivity over a wide pressure range, multifunction, breathability, and excellent wearing comfort, which remains a challenge. To address these issues, an all‐fabric device is designed by loading Ti3C2Tx MXene nanosheets onto woven fabrics through a simple dip‐coating method and sewing three fabric layers with different coating concentrations. The large resistance difference between the high‐resistance middle layer and the low‐resistance outer layer dominates the pressure sensing performance, whereas the two outer layers act as an extraction electrode and flexible Joule heater. The change in internal contact resistance of the trilayer fabric under pressure produces an ultrasensitive (2882–36328 kPa−1) pressure sensor over a wide pressure range (0–140 kPa), whereas sensitivity and detection limit can be regulated by controlling the coating concentration of the middle layer. In addition, the all‐fabric structure endows the sensor with excellent wearing comfort. Multilevel and multiscale applications such as pulse contour, high load motion, tactile interface array, and large‐area wearable heater demonstrate the broad application prospects in wearable healthcare electronics of the trilayer fabric.