Water Spider-Inspired Nanofiber Coating with Sustainable Scale Repellency via Air-Replenishing Strategy

Bioinspired Materials for Controlling Mineral Adhesion: From Innovation Design to Diverse Applications

The advancement of controllable mineral adhesion materials has significantly impacted various sectors, including industrial production, energy utilization, biomedicine, construction engineering, food safety, and environmental management. Natural biological materials exhibit distinctive and controllable adhesion properties that inspire the design of artificial systems for controlling mineral adhesion. In recent decades, researchers have sought to create bioinspired materials that effectively regulate mineral adhesion, significantly accelerating the development of functional materials across various emerging fields. Herein, we review recent advances in bioinspired materials for controlling mineral adhesion, including bioinspired mineralized materials and bioinspired antiscaling materials. First, a systematic overview of biological materials that exhibit controllable mineral adhesion in nature is provided. Then, the mechanism of mineral adhesion and the latest adhesion characterization between minerals and material surfaces are introduced. Later, the latest advances in bioinspired materials designed for controlling mineral adhesion are presented, ranging from the molecular level to micro/nanostructures, including bioinspired mineralized materials and bioinspired antiscaling materials. Additionally, recent applications of these bioinspired materials in emerging fields are discussed, such as industrial production, energy utilization, biomedicine, construction engineering, and environmental management, highlighting their roles in promoting or inhibiting aspects. Finally, we summarize the ongoing challenges and offer a perspective on the future of this charming field.

Self-cleaning electrode for stable synthesis of alkaline-earth metal peroxides

Alkaline-earth metal peroxides (MO2, M = Ca, Sr, Ba) represent a category of versatile and clean solid oxidizers, while the synthesis process usually consumes excessive hydrogen peroxide (H2O2). Here we discover that H2O2 synthesized via two-electron electrochemical oxygen reduction (2e- ORR) on the electrode surface can be efficiently and durably consumed to produce high-purity MO2 in an alkaline environment. The crucial factor lies in the in-time detachment of in situ-generated MO2 from the self-cleaning electrode, where the solid products spontaneously detach from the electrode to solve the block issue. The self-cleaning electrode is achieved by constructing micro-/nanostructure of a highly active catalyst with appropriate surface modification. In experiments, an unprecedented accumulated selectivity (~99%) and durability (>1,000 h, 50 mA cm-2) are achieved for electrochemical synthesis of MO2. Moreover, the comparability of CaO2 and H2O2 for tetracycline degradation with hydrodynamic cavitation is validated in terms of their close efficacies (degradation efficiency of 87.9% and 93.6% for H2O2 and CaO2, respectively).

Fireproof Cavity Structure with Enhanced Impact Resistance and Thermal Insulation toward Safeguarding

Developing devices emphasizing safety protection is becoming increasingly important due to the widespread occurrence of impact damage and thermal hazards. Herein, the F-SSG/TPU-based circular cavity structure (FC) is developed through a convenient and efficient template method, which can effectively achieve anti-impact and thermal insulation for protection. The flame-retardant shear stiffening gel/thermoplastic urethane (F-SSG/TPU) is synthesized through the dynamic interaction between the SSG, TPU, and modified ammonium polyphosphate (APP@UiO-66-NH2) by thermo-solvent reactions. The developed FC can dissipate the impact force from 4.19 to 0.99 kN at 45 cm impacting heights, indicating good anti-impact performance. Moreover, the thermal insulation test demonstrates that the FC achieves a temperature drop of 76 °C at 160 °C attributed to the unique cavity structure design. Under the continuous shock of high-temperature flame, FC remains intact, and its performance is almost undamaged. These results elaborate that the designed FC can effectively resist various damage, such as high-temperature shock and collision. Then, a wearable wristband integrated with FC is developed which exhibits superior impact resistance and heat insulation properties compared with commercial wristbands. In short, this cavity structure based on high-performance F-SSG/TPU material shows promising potential applications in the protection field.

A water strider-inspired intestinal stent actuator for controllable adhesion and unidirectional biofluid picking

Soft-bodied aquatic organisms exhibit extraordinary navigation and mobility in liquid environments which inspiring the development of biomimetic actuators with complex movements. Stimulus-responsive soft materials including hydrogels and shape-memory polymers are replacing traditional rigid parts that leading to dynamic and responsive soft actuators. In this study, we took inspiration from water strider to develop a biomimetic actuator for targeted stimulation and pH sensing in the gastrointestinal tract. We designed a soft and water-based Janus adhesive hydrogel patch that attaches to specific parts of the intestine and responds to pH changes through external stimulation. The hydrogel patch that forms the belly of the water strider driver incorporates an inverse opal microstructure that enables pH responsive behavior. The hydrogel patch on the water strider's leg uses a sandwich structure of Cu particles to convert light into heat and bend under infrared light to mimic the water strider's leg simulating the efficient and steady movement of the water strider's leg which transporting the biological fluid in one direction. This miniature bionic actuator demonstrates controlled adhesion and unidirectional biofluid delivery capabilities, proving its potential for targeted stimulus response and pH sensing in the gastrointestinal tract, thus opening up new possibilities for medical applications in the growing field of soft actuators.

Pyramid-Shaped Superhydrophobic Surfaces for Underwater Drag Reduction

Superhydrophobic surfaces hold immense potential in underwater drag reduction. However, as the Reynolds number increases, the drag reduction rate decreases, and it may even lead to a drag increase. The reason lies in the collapse of the air mattress. To address this issue, this paper develops a pyramid-shaped robust superhydrophobic surface with wedged microgrooves, which exhibits a high gas fraction when immersed underwater and good ability to achieve complete spreading and recovery of the air mattress through air replenishment in the case of collapse of the air mattress. Pressure drop tests in a water tunnel confirm that with continuous air injection, the drag reduction reaches 64.8% in laminar flow conditions, substantially greater than 38.4% in the case without air injection, and can achieve 50.8% drag reduction in turbulent flow. This result highlights the potential applications of superhydrophobic surfaces with air mattress recovery for drag reduction.

Self-Driven Gas Spreading on Mesh Surfaces for Regeneration of Underwater Superhydrophobicity

Underwater superhydrophobic surfaces stand as a promising frontier in technological applications such as drag reduction, antifouling, and anticorrosion. Unfortunately, the air film, known as the plastron, on these surfaces tends to be unstable. To address this problem, active approaches have been designed to preserve or restore plastrons. In this work, a self-driven gas spreading superhydrophobic mesh (SHM) surface is designed to facilitate recovery of the plastron. The immersed SHM can be "wetted" by gas, even when the plastron is removed. We demonstrate that the injected gas can spread spontaneously along the SHM over a large area, which greatly simplifies the plastron replenishment process. By incorporating a locally coated gas-producing layer, we achieve rapid in situ plastron recovery and long-term immersion stability, extending the plastron lifespan by at least 48 times. We also provide a framework for designing an SHM with suitable structural dimensions for gas spreading. Furthermore, an SHM with asymmetric structural dimensions enables unidirectional gas transport by the capillary pressure difference. This SHM surface shows excellent drag reduction properties (37.2%) and has a high slip recovery coefficient (73.4%) after plastron loss. This facile and scalable method is expected to broaden the range of potential applications involving nonwetting-related fields.

Manipulation of bubble collapse patterns near the wall of an adherent gas layer

This paper aims to apply experimental methods to investigate the effect of the thickness of gas layers on the wall on the collapse direction of spark-induced bubbles. In the experiment, two high-speed cameras synchronously record the time evolution of the bubbles and the corresponding parameters such as the normalized collapse position and bubble collapse time. Experiments yielded results for individual bubbles over a range of normalized distances from 0 to 4.0 for different air layer thicknesses. Based on the morphology of the bubbles, the experimental jets were visualized into six different modes, namely, forward jet (FJ), merging jet (MJ), bidirectional jet (BJ), reversing jet (RJ), forward followed by reversing jet (FRJ), and non-directional jet (NDJ). The height of the air layer on the wall is affected by the fluctuation of the bubble volume and shows the opposite trend to the change of the bubble volume. The air film reaches its maximum height when the bubble collapses, which affects the final jet pattern. In addition, as the thickness of the air layer increases, the center of the bubble gradually migrates away from the wall. The different collapse modes and the migration of the bubble centers have positive significance for reducing cavitation erosion in engineering.