Self-Powered and Self-Healable Extraocular-Muscle-Like Actuator Based on Dielectric Elastomer Actuator and Triboelectric Nanogenerator.

Although dielectric elastomer actuators (DEAs) are promising artificial muscles for use as visual prostheses in patients with oculomotor nerve palsy (ONP), high driving voltage coupled with vulnerable compliant electrodes limits their safe long-term service. Herein, a self-healable polydimethylsiloxane compliant electrode based on reversible imine bonds and hydrogen bonds is prepared and coated on an acrylic ester film to develop a self-healable DEA (SDEA), followed by actuation with a high-output triboelectric nanogenerator (TENG) to construct a self-powered DEA (TENG-SDEA). Under 135.9 kV mm-1 , the SDEA exhibits an elevated actuated strain of 50.6%, comparable to the actuation under DC power. Moreover, the mechanically damaged TENG-SDEA displays a self-healing efficiency of over 90% for 10 cycles. The TENG ensures the safe using of TENG-SDEAs and an extraocular-muscle-like actuator with oriented motion ability integrated by several TENG-SDEAs is constructed. Additionally, the SDEA is directly used as a flexible capacitive sensor for real-time monitoring of the patient's muscle movement. Accordingly, a medical aid system based on a conjunction of the extraocular-muscle-like actuator and a flexible capacitive sensor is manufactured to help the patients suffering from ONP with physical rehabilitation and treatment.

An environmental energy-enhanced solar steam evaporator derived from MXene-decorated cellulose acetate cigarette filter with ultrahigh solar steam generation efficiency.

Although solar energy is promising for water purification, there is still a room for further improving the solar steam generation efficiency. Herein, an environmental energy-enhanced solar steam evaporator is fabricated by immersing a cellulose acetate fiber-based cigarette filter (CF) in an aqueous solution of polyvinyl alcohol (PVA) followed by freeze-drying and decorating with MXene sheets. The presence of MXene is to absorb solar light and convert solar energy to thermal energy for efficient water evaporation, while the porous PVA network generated inside the pores of the filter during the freeze-drying process accommodates the dispersed MXene sheets and interconnects the CF and MXene. Because of the constructed PVA/MXene network inside the CF porous architecture and the hydrophilic feature of both MXene and PVA, the resultant MXene/PVA modified CF (MPCF) is highly hydrophilic and competent for rapid upward transfer of water. Interestingly, in addition to the normal energy input by the incident solar light, the large-area sidewall of MPCF gains thermal energy from the environment in the forms of heat convection and heat radiation to enhance the solar steam generation efficiency, resulting in an ultrahigh water evaporation rate of 3.38 kg m-2 h-1 with an outstanding evaporation efficiency of 132.9%.

Hollow-structured MXene-PDMS composites as flexible, wearable and highly bendable sensors with wide working range.

Although versatile piezoresistive pressure sensors show a great potential as human motion detection and wearable smart devices, it is still an issue to widen their working range and enhance their sensitivity. Herein, hollow-structured MXene-polydimethylsiloxane composites (MPCs) are fabricated by utilizing nickel foam as the three-dimensional substrate for dip-coating of MXene sheets followed by infiltrating of polydimethylsiloxane and etching of the nickel foam substrate. The resultant MPC performs a wide working range with bending angles of 0° to 180°, an excellent long-term reliability up to 1000 cycles under the bending angles of 15°, 30° and 150°, and a stable durability with a bending angle of 30° in a frequency range from 0.05 to 2 Hz as a bendable piezoresistive pressure sensor, which is attributed to the formation of dense conduction paths due to the interconnection of MXene sheets during the deformation of MPC. The sensor also exhibits an extremely low detection limit of 10 mg for pressure detection. Interestingly, the slippage of adjacent MXene sheets is beneficial for monitoring slight vibration of equipments and detecting subtle human motions. Thus, the MPC sensor could be applied for stereo sound and ultrasonic vibration monitoring, swallowing, facial muscle movement, and various intense motion detections, demonstrating its great potential as wearable smart devices.

The location and extent of exfoliation of clay on the fracture mechanisms in nylon 66-based ternary nanocomposites.

The primary focus of this work is to elucidate the location and extent of exfoliation of clay on fracture (under both static and dynamic loading conditions) of melt-compounded nylon 66/clay/SEBS-g-MA ternary nanocomposites fabricated by different blending sequences. Distinct microstructures are obtained depending on the blending protocol employed. The state of exfoliation and dispersion of clay in nylon 66 matrix and SEBS-g-MA phase are quantified and the presence of clay in rubber is shown to have a negative effect on the toughness of the nanocomposites. The level of toughness enhancement of ternary nanocomposites depends on the blending protocol and the capability of different fillers to activate the plastic deformation mechanisms in the matrix. These mechanisms include: cavitation of SEBS-g-MA phase, stretching of voided matrix material, interfacial debonding of SEBS-g-MA particles, debonding of intercalated clay embedded inside the SEBS-g-MA phase, and delamination of intercalated clay platelets. Based on these results, new insights and approaches for the processing of better toughened polymer ternary nanocomposites are discussed.

α-Fe2O3 Nanodisk/Bacterial Cellulose Hybrid Membranes as High-Performance Sulfate-Radical-Based Visible Light Photocatalysts under Stirring/Flowing States.

High activity and long-term stability are particularly important for peroxymonosulfate (PMS)-based degradation processes in wastewater treatment, especially under a flowing state. However, if the highly active nanomaterials are in a powder form, they could disperse well in water but would not be convenient for application under varied flow rates. A metal oxide/bacterial cellulose hybrid membrane fixed in a flowing bed is expected to solve these problems. Herein, α-Fe2O3 nanodisk/bacterial cellulose hybrid membranes as high-performance sulfate-radical-based visible light photocatalysts are synthesized for the first time. The bacterial cellulose with excellent mechanical stability and film-forming feature not only benefits the formation of a stable membrane to avoid the separation and recycling problems but also helps disperse and accommodate α-Fe2O3 nanodisks and thus enhances the visible light absorption performances, leading to an excellent PMS-based visible light degradation efficiency under both stirring and flowing states. Particularly, the optimized hybrid membrane photocatalyzes both cationic and anionic organic dyes under a flowing bed state for at least 84 h with the catalytic efficiency up to 100% and can be easily separated after the reaction, confirming its remarkable catalytic performance and long-term stability. Even under varied flow rates during the continuous process, it efficiently degrades rhodamine B and orange II from 3 to 16 mL h-1. When the flow rate goes back from high to low, the hybrid membrane quickly recovers its original performance, demonstrating the high activity and stability of the α-Fe2O3/bacterial cellulose membrane.

Polylactic Acid Nanofiber Scaffold Decorated with Chitosan Islandlike Topography for Bone Tissue Engineering.

In this work, a bicomponent scaffold with a core-shell and islandlike structure that combines the respective advantages of polylactic acid (PLA) and chitosan (CS) was prepared via electrospinning accompanied by automatic phase separation and crystallization. The objective of this research was to design nanosized topography with highly bioactive CS onto PLA electrospun fiber surface to improve the cell biocompatibility of the PLA fibrous membrane. The morphology, inner structure, surface composition, crystallinity, and thermodynamic analyses of nanofibers with various PLA/CS ratios were carried out, and the turning mechanism of a core-shell or islandlike topography structure was also speculated. The mineralization of hydroxyapatite and culture results of preosteoblast (MC3T3-E1) cells on the modified scaffolds indicate that the outer CS component and rough nanoscale topography on the surface of the nanofibers balanced the hydrophilicity and hydrophobicity of the fibers, enhanced their mineralization ability, and made them more beneficial for the attachment and growth of cells. Moreover, CS and "islandlike" protrusions on the fiber surface increased the alkaline phosphatase activity of the MC3T3-E1 cells seeded on the fibrous membrane and provided a more appropriate interface for cell adhesion and proliferation. These results illustrate that this kind of PLA/CS membrane has the potential in tissue engineering. More importantly, our study provides a new approach to designing PLA scaffolds, with combined topographic and bioactive modification effects at the interface between cells and materials, for biomedicine.

Improved electrical conductivity of polyamide 12/graphene nanocomposites with maleated polyethylene-octene rubber prepared by melt compounding.

Electrically conductive polyamide 12 (PA12)/graphene binary nanocomposites with a low percolation threshold of 0.3 vol % were prepared by melt compounding. A rapid increase in electrical conductivity from 2.8 × 10(-14) S/m of PA12 to 6.7 × 10(-2) S/m was achieved with ~1.38 vol % graphene. It is shown that graphene sheets were homogeneously dispersed in PA12 matrix. Furthermore, polyethylene-octene rubber grafted with maleic anhydride (POE-g-MA) was used to further enhance the electrical conductivity of PA12/graphene nanocomposites. Three compounding sequences were adopted to tailor the microstructure and properties of the ternary nanocomposites. Both highest electrical conductivity and storage modulus were obtained when most graphene sheets were located in PA12 matrix rather than in POE-g-MA phase.

Growth of silver nanocrystals on graphene by simultaneous reduction of graphene oxide and silver ions with a rapid and efficient one-step approach.

A rapid and efficient one-step approach to prepare graphene-Ag nanocomposites by simultaneous reduction of graphene oxide (GO) and silver ions with formaldehyde as the reducing agent within several minutes was demonstrated.

Tough graphene-polymer microcellular foams for electromagnetic interference shielding.

Functional polymethylmethacrylate (PMMA)/graphene nanocomposite microcellular foams were prepared by blending of PMMA with graphene sheets followed by foaming with subcritical CO(2) as an environmentally benign foaming agent. The addition of graphene sheets endows the insulating PMMA foams with high electrical conductivity and improved electromagnetic interference (EMI) shielding efficiency with microwave absorption as the dominant EMI shielding mechanism. Interestingly, because of the presence of the numerous microcellular cells, the graphene-PMMA foam exhibits greatly improved ductility and tensile toughness compared to its bulk counterpart. This work provides a promising methodology to fabricate tough and lightweight graphene-PMMA nanocomposite microcellular foams with superior electrical and EMI shielding properties by simultaneously combining the functionality and reinforcement of the graphene sheets and the toughening effect of the microcellular cells.

Enhanced electrical conductivity in polystyrene nanocomposites at ultra-low graphene content.

We compared the electrical conductivity of multiwalled-carbon-nanotube/polystyrene and graphene/polystyrene composites. The conductivity of polystyrene increases from ∼6.7 × 10(-14) to ∼3.49 S/m, with an increase in graphene content from ∼0.11 to ∼1.1 vol %. This is ∼2-4 orders of magnitude higher than for multiwalled-carbon-nanotube/polystyrene composites. Furthermore, we show that the conductivity of the graphene/polystyrene system can be significantly enhanced by incorporation of polylactic acid. The volume-exclusion principle forces graphene into the polystyrene-rich regions (selective localization) and generates ∼4.5-fold decrease in its percolation threshold from ∼0.33 to ∼0.075 vol %.