With the rapid development of the electronics industry, smart wearable electronics and electromagnetic interference (EMI) shielding materials have attracted tremendous interest. However, it is still a great challenge to maintain stable performance after damage. Herein, we prepare a super-stretchable and self-healing hydrogel composite with EMI shielding performance by the in situ polymerization of the acrylamide (AAm) and N-acryloyl-11-aminoundecanoic acid (A-11) in the silver nanowires (AgNWs) aerogel with cellular structure. Benefiting the continuous three-dimensional AgNWs network, the hydrogel composite has high electrical conductivity (83 S/cm), outstanding resistance-strain response of more than 800% tensile strain, and exceptional EMI effectiveness (SE) of 66 dB in X-band, capable of monitoring human motions as a wearable sensor. Moreover, the reversible hydrophobic association and hydrogen bonding interactions endow the hydrogel composite with excellent self-healing capability (EMI SE healing efficiency of 90%). The healed hydrogel composite can still serve as a sensor to respond rapidly and steadily to human motions. The super-stretchable and self-healing hydrogel composite holds great promise for smart wearable electronics and EMI shielding.
Abstract Developing multimodal sensors with human‐like tactile perception is highly desirable for wearable devices, electronic skins (e‐skins), and human‐machine interfaces. However, realizing decoupled signal output and high‐precision measurement remains challenging. Superelastic conductive aerogels are ideal materials for fabricating multimodal sensors as they can convert pressure and temperature stimuli into different electrical signals. Herein, inspired by the microstructure of lightweight and robust avian bones, a biomimetic lamellar silica nanofiber/MXene aerogel (LSMA) sensor for decoupled pressure and temperature sensing is first developed. The avian bone‐like lamellae‐strut structure endows the ultralight LSMA with superb fatigue resistance of 99.1% height retention after 10 000 compression cycles, which is second to none in the reported MXene‐based aerogels. Meanwhile, benefiting from the advantages of the aerogel structure, the LSMA sensor integrating piezoresistive and thermoelectric effects has an ultrahigh temperature resolution of 0.07 K and the lowest pressure detection limit of 0.20 Pa in the reported pressure‐temperature sensors. The unique performance renders it a promising platform for wearable physiological monitoring and tactile e‐skin. Furthermore, an innovative multilevel encryption protection system assisted by machine learning is designed based on the LSMA sensing array as the interactive terminal. This study provides novel insights into the design and application of multimodal sensors.
An extreme condition-resistant SNF/MXene composite aerogel sensor that can synchronously perform motion monitoring and thermal management is fabricated by an ice-templating assembly strategy.
Typically, the basic method to enhance the dielectric response of polymer-based composites is to fill giant dielectric ceramic fillers, such as BaTiO3 and CaCu3Ti4O12, into the polymer matrix. Here, by using low-k boron nitride (BN) with well-controlled microstructure and surface, we successfully prepared a high-k polymeric composite, where the improvement in the dielectric constant of the composite even exceeds that of composites containing BaTiO3 and CaCu3Ti4O12 particles at the same weight percent. First, a lamellar boron nitride nanosheet (BNNS) aerogel was prepared by bidirectional freezing and freeze drying, respectively, and then the aerogel was calcined at 1000 °C to obtain the lamellar BNNS skeleton with some hydroxyl groups. Finally, the epoxy resin (EP) was vacuum impregnated into the BNNS skeleton and cured inside to prepare the lamellar-structured BNNSs/EP (LBE) composites. Interestingly, the dielectric constants of LBE with a 10 wt % BNNS content reached 8.5 at 103 Hz, which was higher by 2.7 times than that of pure EP. The experimental data and the finite element simulations suggested that the increased dielectric constants of LBE resulted from the combination of two factors, namely, the lamellar microstructure and the hydroxyl groups. The stacking of the BNNS phase into a highly connected lamellar skeleton significantly increased the internal electric field and the polarization intensity, while the introduction of hydroxyl groups on the BNNS surface further improved the polarization of the composite, resulting in a significant increase in the dielectric constant of the LBE. This work provides a new strategy for improving the dielectric constant through the microstructure design of composites.
In this work, parallel-structured BaTiO 3 /epoxy composites were prepared and excellent dielectric properties were obtained. The composite with 59 vol% content has an ultra-high dielectric constant (2017) and shows low loss (<0.02) at 1 kHz.
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