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Hydrophilic macroporous sponge has been widely used in solar steam generation, catalysis, biosensing and other fields due to its high water transporting and adsorption ability. However, the synthesis step of hydrophilic sponge usually needs the assistance of a freezing process and toxic chemicals such as chemical crosslinkers or foaming agents. To solve these problems, herein, a novel and facile tactic based on the salting out effect was proposed to prepare hydrophilic amphibious open-cell macroporous sponge from the poly(vinyl alcohol) (PVA) solution. Glycerol, CaCl2 and Na3Cit were successively added into PVA solution. The sol–gel transition would occur due to the salting-out effect of Na3Cit and hydrogen bond crosslinking of glycerol. Finally, the hydrophilic PVA sponge with different shapes and sizes could be easily prepared. Moreover, this hydrophilic wet sponge could be room temperature dried into dry sponge and this dry sponge could be quickly restored to wet sponge after immersing in water due to its ultra-rapid water absorption. The microstructure and mechanical properties of PVA wet and dry sponges were studied. The PVA wet sponge showed excellent mechanical properties with a tensile strength, Young's modulus, and fracture energy of 1.51 ± 0.01 MPa, 0.44 ± 0.02 MPa, and 113.2 ± 1.6 kJ m−2, respectively. The wet sponge prepared in this work has an average porosity of up to 50 μm, and the pore structure can still be maintained during the conventional room temperature drying process. Moreover, the PVA sponge showed high stability in various aqueous media including acid, alkaline, and salt solutions. This work provided a simple and large-scale method to prepare amphibious open-cell hydrophilic PVA sponge. [ABSTRACT FROM AUTHOR]

Fiber-reinforced polymer matrix composites during engineering applications can be influenced by critical environmental conditions (e.g., water and temperature), probably causing a negative impact on the mechanical performance. In this work, the hygrothermal aging behavior and flexural property of carbon fiber (CF)-reinforced polyethylene terephthalate glycol (PETG) composites were investigated at different aging temperatures and days. The CF/PETG composites were fabricated using the hot-press molding method. The mathematical fitting model and finite element analysis method were employed to reveal the hygrothermal aging behavior and the moisture absorption evolution. After 90 days of aging, the water uptakes of the specimens at 25°C, 45°C, and 60°C are 0.55%, 0.62%, and 1.67% for PETG and 0.47%, 0.54%, and 1.52% for CF/PETG, respectively. The flexural strengths of the CF/PETG composites at 25°C, 45°C, and 60°C after 90 days of aging decrease by 28.6%, 30.2%, and 32.2% as compared with the non-aging composites, respectively. The water uptakes of the CF/PETG composites tend to increase with the increase in cyclic aging time interval. The flexural strengths of the composites with the cyclic aging intervals of 2, 5, 10, and 15 days first decrease and then increase slightly. The knowledge gained in this study will benefit future design optimization of the CF/PETG composite material and lay the foundation for its engineering application. [ABSTRACT FROM AUTHOR]

Continuous real-time human motion and heart-rate monitoring systems can provide vital clinical information for disease diagnosis, preventive healthcare and rehabilitation care. However, it is still a challenge to design wearable pressure/strain sensors with great flexibility and sustainable power for motion detection and physiological signal monitoring. Here, a self-powered laminated fabric sensor based on Schottky contact was successfully fabricated. This laminated fabric sensor was constructed by sandwiching the polypyrrole (PPy)-coated fabric with the Ni-coated fabric and Al plastic film. The electrical outputs under strain were attributed to the single Schottky contact between PPy and Al. This fabric sensor exhibited excellent stability under continuous quick cycling operation and at high relative humidity, which could be adapted to different human body parts for continuous motion detection and heart-rate monitoring. This work is of great significance to demonstrate a promising strategy toward self-powered wearable pressure sensors used for human motion detecting and hear-rate monitoring. [ABSTRACT FROM AUTHOR]

Thermochromic smart windows are considered to be promising energy-saving devices for reducing energy consumption in buildings. The ideal materials for thermochromic smart windows should have high transmittance, high solar modulation, low phase-transition temperature, and excellent high-temperature thermal stability, which are difficult to achieve simultaneously. This work reports a simple one-step low-temperature polymerization method to prepare a thermo-responsive poly( N -isopropylacrylamide)/hydroxypropylmethyl cellulose (PNIPAM/HPMC) hydrogel achieving the above performances simultaneously. The low-temperature polymerization environment endowed the hydrogel with a high luminous transmittance ( T lum ) of 90.82%. HPMC as a functional material effectively enhanced the mechanical properties and thermal stability of the hydrogel. Meanwhile, the PNIPAM/HPMC hydrogel showed a low phase-transition temperature (∼32 °C) and high solar modulation (Δ T sol = 81.52%), which proved that it is an ideal material for thermochromic smart windows. Moreover, a PNIPAM/HPMC smart window exhibited high light transmittance ( T 380-760 = 86.27%), excellent light modulation (Δ T 365 = 74.27%, Δ T 380-760 = 86.17%, and Δ T 940 = 63.93%), good indoor temperature regulation ability and stability, which indicated that it was an attractive candidate for application in reducing energy consumption in buildings. This work also provides an option and direction for modifying PNIPAM-based thermochromic smart windows.