In recent years, highly sensitive pressure sensors that are flexible, biocompatible, and stretchable have attracted significant research attention in the fields of wearable electronics and smart skin. However, there has been a considerable challenge to simultaneously achieve highly sensitive, low-cost sensors coupled with optimum mechanical stability and an ultralow detection limit for subtle physiological signal monitoring devices. Targeting aforementioned issues, herein, we report the facile fabrication of a highly sensitive and reliable capacitive pressure sensor for ultralow-pressure measurement by sandwiching MXene (Ti 3 C 2 T x )/poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) composite nanofibrous scaffolds as a dielectric layer between biocompatible poly-(3,4-ethylenedioxythiophene) polystyrene sulfonate /polydimethylsiloxane electrodes. The fabricated sensor exhibits a high sensitivity of 0.51 kPa −1 and a minimum detection limit of 1.5 Pa. In addition, it also enables linear sensing over a broad pressure range (0−400 kPa) and high reliability over 10,000 cycles even at extremely high pressure (>167 kPa). The sensitivity of the nanofiber-based sensor is enhanced by MXene loading, thereby increasing the dielectric constant up to 40 and reducing the compression modulus to 58% compared with pristine PVDF-TrFE nanofiber scaffolds. The proposed sensor can be used to determine the health condition of patients by monitoring physiological signals (pulse rate, respiration, muscle movements, and eye twitching) and also represents a good candidate for a next generation human−machine interfacing device.
Recently, flexible capacitive pressure sensors have received significant attention in the field of wearable electronics. The high sensitivity over a wide linear range combined with long-term durability is a critical requirement for the fabrication of reliable pressure sensors for versatile applications. Herein, we propose a special approach to enhance the sensitivity and linearity range of a capacitive pressure sensor by fabricating a hybrid ionic nanofibrous membrane as a sensing layer composed of Ti3C2T x MXene and an ionic salt of lithium sulfonamides in a poly(vinyl alcohol) elastomer matrix. The reversible ion pumping triggered by a hydrogen bond in the hybrid sensing layer leads to high sensitivities of 5.5 and 1.5 kPa–1 in the wide linear ranges of 0–30 and 30–250 kPa, respectively, and a fast response time of 70.4 ms. In addition, the fabricated sensor exhibits a minimum detection limit of 2 Pa and high durability over 20 000 continuous cycles even under a high pressure of 45 kPa. These results indicate that the proposed sensor can be potentially used in mobile medical monitoring devices and next-generation artificial e-skin.
Advancement of sensing systems, soft robotics, and point-of-care testing requires the development of highly efficient, scalable, and cost-effective physical sensors with competitive and attractive features such as high sensitivity, reliability, and preferably reversible sensing behaviors. This study reports a highly sensitive and reliable piezoresistive strain sensor fabricated by one-step carbonization of the MoS2-coated polyimide film to obtain MoS2-decorated laser-induced graphene. The resulting three-dimensional porous graphene nanoflakes decorated with MoS2 exhibit stable electrical properties yielding a reliable output for longer strain/release cycles. The sensor demonstrates high sensitivity (i.e., gauge factor, GF ≈1242), is hysteresis-free (∼2.75%), and has a wide working range (up to 37.5%), ultralow detection limit (0.025%), fast relaxation time (∼0.17 s), and a highly stable and reproducible response over multiple test cycles (>12 000) with excellent switching response. Owing to the outstanding performances of the sensor, it is possible to successfully detect various subtle movements ranging from phonation, eye-blinking, and wrist pulse to large human-motion-induced deformations.
choice for remote areas that have sufficient sunlight. [13][14][15][16][17] However, the main drawback of harvesting light energy is its limitations when operating in dirty or low-light conditions. In this case, wind and rain can be a substitute for natural resources. [18][19][20][21] Traditional hydroelectric power plants require proper land and large capital assets to construct barrages and can be harmful to the environment. Wind turbines have limitations such as complex wind directions, high costs, and large volumes. [22,23] Additionally, conventional generators are created on weighty, rigid, and unbending materials. [24][25][26] The development of local energy harvesters is highly anticipated due to their small volumes, adjustable shapes, costfriendliness, and broad applicability. [27][28][29][30] Human body motions, such as shaking limbs, walking, running, jumping, and breathing, are vibration sources that have attracted the attention of many scholars for energy-harvesting applications. [31][32][33][34] Fabric-based triboelectric nanogenerators (TENGs) have been highlighted for their wearability/portability, environmental friendliness, mechanical stability, and flexibility. These nanogenerators can effectively harvest energy without inhibiting human motion or the environment. In addition, TENGs have outstanding energy conversion efficiencies, low manufacturing costs, and simple structures. TENGs are based on the coupling between the triboelectric effects wherein electrification and charge transfer occur based on contact-separation, sliding, or friction between two dissimilar materials (polymers and metals) depend on the electrostatic induction and triboelectric series. [35][36][37] Fabrics have been used since the dawn of humankind and are important to everyday life. Fabrics are portable, bendable, foldable, rollable, and can be adjusted to our regular environment. [38,39] J. Xiong et al. reported a fabric-based TENG that harvests energy from the water flow. [40] However, water molecules that adhere to the harvester surface can prevent the triboelectric effect and critically inhibit the abilities of TENGs, indicating that the fabric would benefit from a difficult hydrophobicity method. [41] Most conventional and fabric-based TENGs can only harvest energy from one selected source. [42,43] Some research groupsThe triboelectric material properties and mechanical stability of the contact layer are vital to achieving durable triboelectric nanogenerators (TENGs) with high output performance. Herein, a novel MXene/Ecoflex nanocomposite is introduced as a promising triboelectric material because of its highly negative triboelectric properties and mechanical stability. The MXene/Ecoflex nanocomposite with a fabric-based waterproof TENG (FW-TENG) is fabricated and designed to universally harvest energy from various human motions as well as the natural environment (rain and wind). The fabricated FW-TENG delivers a maximum output peak power of 3.69 mW and a power density of 9.24 W m −2 , respectively, at a matching load...
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