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To develop strain sensors with excellent reliability, stability, sensitivity, reversibility, and facile processing still suffers great challenge. In this work, the glass micro-beads (μ-GB) with high modulus were added into poly(ethylene-co-1-octene)/multi-walled carbon nanotubes (POE/MWCNTs) composites to construct modulus mismatching domains, which generated asymmetric deformation in the composites during compression and then improved piezoresistive sensitivity. The μ-GBs with diameter of 45, 75, and 105 μm were used to evaluate the size effect of modulus mismatching domains on the piezoresistive sensitivity of the composites. It was very interesting to find that the composites with different diameter of μ-GBs exhibited different piezoresistive sensitivity. The highest piezoresistive sensitivity was found in the composites with the smallest size of μ-GBs (45 μm). Additionally, the piezoresistive sensitivity was also improved by increasing the content of μ-GBs. For example, the gauge factor of the POE/MWCNTs composites increased from 1.9 to 6.4 by the incorporation of 50 wt% μ-GBs with 45 μm in diameter. The mechanism of the asymmetric deformation in the composites with modulus mismatching domains under cyclic loading was discussed in detail. Furthermore, the strain sensor with μ-GBs had excellent reliability, stability and reversibility, which was attached to a sport shoe and exhibited a good cyclic signal response during walking. Besides, the Young’s modulus and compression modulus were also enhanced by the addition of μ-GBs. For example, the Young's modulus of the POE/MWCNTs composites showed 300% enhancement by adding 50 wt% μ-GBs with 45 μm in diameter.

Electrochromic devices (ECDs) can alter their optical transmittances under external electrical power but are unable to spontaneously modulate the light flow in real-time along with the intensity change of surrounding light. To address this problem, a module of smart perovskite solar cell (PSC)-powered all-in-one gel ECDs was reported. The PSC-powered ECDs could modulate their transmittance swiftly in visible-infrared regions, hence regulating the photo energy flow in real time according to the surrounding light intensity. The ECD based on 4, 4′-(thiophene- 2, 5-diyl)bis(1-ethylpyridin-1-ium) diiodide (TEV) showed large optical contrast (79.7% at 570 nm, 64.9% at 908 nm), excellent coloration efficiency (231.2 cm2/C), and outstanding stability (only 1.1% ΔT change after 60,000 cycles). The PSC-powered ECDs showed fast response time (≤5 s) and high stability (negligible degradation after 5000 s consecutive switching between bright and dark conditions in air). Meanwhile, the stored power accompanied with the electrochromic process could drive a red LED with high cyclic stability (95.6% of areal capacitance maintained after 10,000 charging-discharging cycles), indicating that ECDs can serve as ideal electrochromic supercapacitors (ECSs). In addition, the fabricated ECD with large area (5.0 cm × 5.4 cm) showed excellent thermal regulation (7 °C of temperature difference between colored and bleached states). We expect this work would pave a new way to save energy and improve energy efficiency in modern buildings and automobiles.

Anisotropic conductive composites with segregated conductive networks were constructed in poly( l- lactide)/poly(e-caprolactone)/multi-walled carbon nanotubes/nickel (PLLA/PCL/MWCNT/Ni) composites by aligning Ni particles using a low magnetic field. Firstly, MWCNTs were melt-mixed with PLLA to form PLLA/MWCNT composites and then pulverized into microscale PLLA/MWCNT particles 425–850 μm in size. Later, the Ni particles were dispersed in PCL to yield PCL/Ni composites and then mixed with PLLA/MWCNT particles at 100 °C, a temperature lying in between the melting temperatures of PCL and PLLA. The coated PLLA/MWCNT particles were compressed to form PLLA/PCL/MWCNTs/Ni composites with segregated structures. A remarkable conductive anisotropy was observed in the segregated samples after magnetic alignment in a low magnetic field of ∼47.5 mT at 100 °C for 30 min. The electrical conductivity of the segregated samples diametrically increased in the direction parallel to the magnetic field, but decreased in the direction perpendicular to the magnetic field after the magnetic alignment of Ni particles in the PCL phase. Electrical conductivity in the parallel direction was almost eight orders of magnitude higher than that in the perpendicular direction at 3.0 wt% Ni and 0.7 wt% MWCNTs. Conductive anisotropy in the segregated systems could also be easily regulated by controlling the treatment time or changing the direction of the magnetic field. However, electrical conductivity could be maintained in both vertical and parallel directions in conventional composites after magnetic treatment because Ni particles preferably dispersed in the continuous PLLA phase, in which the Ni particles cannot be aligned at 100 °C. In addition, these segregated samples with alignment of Ni particles also exhibited the mechanical enhancement and high-performance electromagnetic interference shielding.

Liquid metal (LM) is a promising candidate for electromagnetic interference (EMI) shielding due to the superb electrical conductivity and easy processing. However, poor compatibility caused by high surface tension, insulated oxide shells formed during processing, and unmanageable fluidity at elevated temperature of LM severely hinder its application in the field of EMI shielding. Herein, we develop a novel processing strategy integrating ball-milling dispersion, freeze-drying and compression molding to achieve free-standing and flexible LM/cellulose nanofiber composites (LM/CNF) film, in which the oxide shells of LM droplets generated by ball-milling are broken by mechanical compression, and LM droplets are coalesced while confined by CNF to construct a continuously conductive path. As a result, the robust LM/CNF film shows tensile strength of above 30 MPa, and it possesses electrical conductivity of 96,000 S/m, leading to remarkable shielding effectiveness (SE) of above 65 dB with a thickness of only 300 µm in a broad frequency range of 4–18 GHz covering C-band, X-band and Ku-band. Moreover, LM/CNF film exhibits excellent structural stability and EMI shielding performance reliability after high-temperature treatment. Besides, simulation in the frequency domain with ANSYS HFSS 2019 R2 is performed to intuitively understand the shielding mechanism of LM/CNF film. It is found that the attenuation of electromagnetic waves is mainly based on reflection. This study proposes a fresh scenario to achieve high-performance EMI shielding material and paves the way for potential applications of LM in portable and wearable smart electronics.

Ti3C2Tx MXene with two-dimensional (2D)-layered structure shows potential application in various fields owing to its superb metallic conductivity and excellent solution processability. However, a fundamental challenge limiting the implementation of Ti3C2Tx in practical applications is its susceptibility to oxidation in either humid or aqueous environments only within a few days, which results in the disassembly of the 2D-layered structure and severely deteriorates the functional properties including electrical conductivity, mechanical strength and EMI shielding performance. Herein, we firstly demonstrate a robust procedure to protect sensitive Ti3C2Tx from degradation by modification with imidazolium-based inion liquid (IL), which remarkably improves the chemical stability of Ti3C2Tx in aqueous and significantly increases the mechanical strength of assembled freestanding Ti3C2Tx film (IL-MXene). The crystalline structure of IL-MXene sheet remains intact up to 30 days and preserves the 2D-layered structure as long as 8 months in aqueous, meanwhile, the tensile strength of freestanding IL-MXene film is as high as 75.9 ± 4.9 MPa and the increment is up to 84% when compared to that of untreated MXene film (41.2 ± 4.5 MPa). A novel mechanism for improved chemical stability of MXene sheet was proposed and elucidated based on the radical-scavenging ability of IL and the surface chemistry of MXene sheet. This study provides a new strategy to achieve chemically stable Ti3C2Tx and improved mechanical strength of assembled MXene film, which is also available for other type of MXenes.

This contribution proposes an adiabatic criterion ( cri ad ) for online detection of thermal runaway region and determination of the real-time acceptable accumulation in a semibatch process. The cri ad is deduced based on a mathematic analysis of the mass and heat balance equations of semibatch reactors. It states that the semibatch processes are in a potential runaway situation if the value of cri ad is positive on a segment of the reaction path. Furthermore, the numerical simulations for semibatch second order reactions were performed under isoperibolic and isothermal operating conditions verify the validation of the cri ad . To take advantage of this criterion, the information on real-time temperature of the reaction mixture and conversion of the reactants are required. Specifically, the temperature of reaction mixture can be directly measured, while the conversion of the reactants can be online measured through a modified reaction calorimetry method. This criterion can potentially contribute to optimize the feeding profile as a safety constraint as well as enhance the inherent safety of the semibatch processes.