Seawater-enhanced tough agar/poly(N-isopropylacrylamide)/clay hydrogel for anti-adhesion and oil/water separation

Tolerant chitosan/carboxymethyl cellulose@calcium composite films on nylon fabric for high-flux water/oil separation

Nacre as a natural organic-inorganic composite has outstanding mechanical toughness and oil repellency. Enlightened by nacre, we present here a novel strategy to fabricate superhydrophilic/underwater superoleophobic hybrid films on nylon fabric (NF). The hybrid films were constructed via facile and green layer-by-layer (LbL) assembly of calcium ion (Ca²⁺), chitosan (CS), and carboxymethyl cellulose (CMC) combined with biomimetic mineralization in CO₂ atmosphere. The resulting NF exhibits excellent superoleophobicity underwater, anti-oil-fouling ability, and stability. Under the drive of gravity, the deposited fabric can selectively remove pure and corrosive water from various oil-containing water with preferable separation efficiencies, great water flux (>6903 L·m^-2·h^-1), favorable oil penetration pressure (1.47 kPa), and outstanding recyclability. Especially, the NF can still sustain high underwater oleophobicity after repeatedly separating oil/corrosive water for 80 times. The green preparation process, eco-friendly and durable coating, and good separation performance allow the as-fabricated NF to be applied in oily wastewater treatment.

Solar-assisted high-efficient cleanup of viscous crude oil spill using an ink-modified plant fiber sponge

Rapid and efficient clean-up of viscous crude oil spills is still a global challenge due to its high viscous and poor flowability at room temperature. The hydrophobic/oleophilic absorbents with three-dimensional porous structure have been considered as a promising candidate to handle oil spills. However, they still have limited application in recovering the high viscous oil. Inspired by the viscosity of crude oil depended on the temperature, a solar-heated ink modified plant fiber sponge (PFS@GC) is fabricated via a simple and environmentally friendly physical foaming strategy combined with in-situ ink coating treatment. After wrapping by the polydimethylsiloxane (PDMS), the modified PFS@GC (PFS@GC@PDMS) exhibits excellent compressibility, high hydrophobic (141° in water contact angle), solar absorption (> 96.0%), and oil absorptive capacity (12.0-27.8 g/g). Benefiting from the favorable mechanical property and photothermal conversion capacity, PFS@GC@PDMS is demonstrated as a high-performance absorbent for crude oil clean-up and recovery. In addition, PFS@GC@PDMS can also be applied in a continuous absorption system for uninterrupted recovering of oil spills on the water surface. The proposed solar-heated absorbent design provides a new opportunity for exploring biomass in addressing large-scale oil spill disasters.

Extreme Temperature-Tolerant Conductive Gel with Antibacterial Activity for Flexible Dual-Response Sensors

Flexible sensors based on conductive hydrogel show great potential in electronic skin and human-machine interface. However, pure water in hydrogel inevitably freezes or rapidly evaporates under extreme temperatures, leading to inadequate fulfillment of sensor performances. Herein, a well-designed strategy is reported for fabricating extreme temperature-tolerant gel-based sensors. By immersing a gelatin/polyacrylamide (PAAm)-clay composite (GC) hydrogel into a ZnCl₂/water/glycerol system, a phase-transition-tunable gel (PTTGC gel) is obtained with outstanding antifreezing (-82 °C) and long-lasting moisture (70 °C, more than 40 days) properties. Meanwhile, the gel also presents good antibacterial activity and biocompatibility attributing to Zn²⁺ and gelatin, respectively. Then, a dual-response sensor with a wide operating temperature (-60 to 60 °C) is proposed, presenting high stress and temperature sensitivities and long-term stability. The sensor will meet the needs of the human-machine interface for scientific investigation and data monitoring in polar, desert, etc.

Multistimuli-Responsive Optical Hydrogel Nanomembranes to Construct Planar Color Display Boards for Detecting Local Environmental Changes

Planar metal-insulator-metal (MIM) optical cavities are attractive for biochemical and environmental sensing applications, as they offer a cost-effective cavity platform with acceptable performances. However, localized detection and scope of expansion of applicable analytes are still challenging. Here, we report a stimuli-responsive color display board that can exhibit local spectral footprints, for locally applied heat and alcohol presence. A thermoresponsive, optically applicable, and patternable copolymer, poly(N-isopropylacrylamide-r-glycidyl methacrylate), is synthesized and used with a photosensitive cross-linker to produce a responsive insulating layer. This layer is then sandwiched between two nanoporous silver membranes to yield a thermoresponsive MIM cavity. The resonant spectral peak is blue-shifted as the environmental temperature increases, and the dynamic range of the resonant peak is largely affected by the composition and structure of the cross-linker and the copolymer. The localized temperature increase of silk particles with gold nanoparticles by laser heating can be measured by reading the spectral shift. In addition, a free-standing color board can be transferred onto a curved biological tissue sample, allowing us to simultaneously read the temperature of the tissue sample and the concentration of ethanol. The stimuli-responsive MIM provides a new way to optically sense localized environmental temperature and ethanol concentration fluctuations.

Grafting polysiloxane onto ultrafiltration membranes to optimize surface energy and mitigate fouling

Conventional approaches to mitigate fouling of membrane surfaces impart hydrophilicity to the membrane surface, which increases the water of hydration and fluidity near the surface. By contrast, we demonstrate here that tuning the membrane surface energy close to that of the dispersive component of water surface tension (21.8 mN m^-1) can also improve the antifouling properties of the membrane. Specifically, ultrafiltration (UF) membranes were first modified using polydopamine (PDA) followed by grafting of amine-terminated polysiloxane (PSi-NH₂). For example, with 2 g L^-1 PSi-NH₂ coating solution, the obtained coating layer contains 53% by mass fraction PSi-NH₂ and exhibits a total surface energy of 21 mN m^-1, decreasing the adsorption of bovine serum albumin by 44% compared to the unmodified membrane. When challenged with 1 g L^-1 sodium alginate in a constant-flux crossflow system, the PSi-NH₂-grafted membrane exhibits a 70% lower fouling rate than the pristine membrane at a water flux of 110 L (m² h)^-1 and good stability when cleaned with NaOH solutions.