Dengke Chen

Mechanical seal faces frequently operate under harsh and dynamic conditions, where maintaining stable and efficient lubrication remains a critical challenge. Surface texturing has emerged as an effective approach to improve the lubrication and tribological performance of sealing end faces. This study investigates the lubrication behavior and sealing characteristics of squamous textured mechanical sealing faces through a combination of sealing experiments and mixed lubrication modeling. The results indicate that during start-up, increasing rotational speed enhances the load-carrying capacity and reduces contact force, resulting in thicker lubricant films and lower friction coefficients. Consequently, the sealing interface gradually transitions from mixed to hydrodynamic lubrication. Moreover, with increasing medium pressure, both the critical rotational speed and duration required for this lubrication regime transition increase. Under various steady periods, smooth seal faces predominantly operate in the mixed lubrication regime, whereas textured faces maintain hydrodynamic lubrication, reducing the average friction coefficient and temperature rise by 69.5% and 51.8%, respectively. These findings provide crucial insights into the performance improvement and practical applications of squamous textures for high-efficiency, long-lifespan mechanical seals.

Achieving efficient drag reduction and antifouling on high-speed moving surfaces in viscous fluids remains a significant technological challenge. Over millions of years of evolution, natural organisms have developed unique surface microstructures that effectively minimize surface frictional resistance (SFR) and mitigate biofouling in complex environments. Therefore, investigating the intrinsic relationship between the unique surface structures of organisms and drag reduction/antifouling functions can provide innovative inspirations for the design of high-speed surfaces with minimized SFR and biofouling. Compared with air environment, the marine environment is more complicated and considered more representative. Fish, as a typical representative of marine organisms, have excellent fluid dynamics and antifouling capacities. Therefore, the shark—an apex marine predator—was selected as a biological prototype. Beginning with the structural characteristics of sharkskin denticles, the review offers a detailed discussion of fabrication techniques for manufacturing biomimetic denticle-inspired surfaces, Sharklet AF^TM and biomimetic Sharklet patterns. Furthermore, the effects and mechanisms responsible for drag reduction and antifouling in these bioinspired surfaces are systematically examined. Finally, applications of biomimetic non-smooth surfaces in aerospace, biomedicine, and other domains are briefly discussed. The current state of research and future directions in technologies for biomimetic non-smooth surfaces are outlined, highlighting the lack of comprehensive reviews in underexplored fields such as aviation. This study aims to serve as a valuable reference for the design and development of multifunctional biomimetic surfaces.

The global shortage of freshwater resources is intensifying, prompting the development of solar-driven interfacial evaporation as a promising solution. However, the scalability of existing evaporators remains limited due to high costs, complex fabrication, insufficient stability, and poor salt tolerance. Traditional polymer-based Janus membranes also exhibit low mechanical strength and inadequate weather resistance. While some carbon-based or composite evaporators have demonstrated high performance, their large-scale application is hindered by expensive materials and intricate manufacturing processes. To address these limitations, this study utilizes low-cost commercial melamine foam (MF) as a substrate. Through sol-gel synthesis and spray coating, a Janus-structured CB-PDMS/PMF evaporator is fabricated by compositing carbon black (CB) and polydimethylsiloxane (PDMS) onto the MF surface. The design innovatively employs a water-isolation method to precisely control the thickness of the photothermal layer and the flatness of the evaporation interface. The upper hydrophobic photothermal layer (P layer) absorbs and converts light, while the lower hydrophilic water-transport layer (W layer) enables capillary-driven water supply and self-floating capability, thereby minimizing heat loss. Furthermore, a surface-patterned honeycomb structure enhances light absorption via multireflection, and the Marangoni effect is leveraged to suppress salt accumulation, ensuring excellent salt rejection. Experimental results demonstrate that the optimized Eva-4 evaporator achieves a stable evaporation rate of 1.1 kg·m^-2·h^-1 under 1 kW·m^-2 solar irradiation, with a photothermal conversion efficiency of 75%. It exhibits robust cycling stability, neutralizes strongly acidic/alkaline feedwaters, and produces desalinated water that meets WHO drinking standards. Moreover, the evaporator maintains high salt tolerance across varying salinities. This work provides a cost-effective, scalable approach based on simple fabrication techniques, advancing the application of solar-driven interfacial evaporation for large-scale desalination and wastewater remediation.

Reducing surface friction resistance (SFR) is beneficial for the performance of high‐speed marine equipment surfaces. To reduce SFR, a biomimetic surface was developed through a collaborative multi‐process strategy involving a combination of laser ablation and spraying techniques. Initially, biomimetic fish scale (BFS) arrays with five different spacing ( s ) values were fabricated on an aluminium (Al) substrate using laser ablation, which was then replicated with polydimethylsiloxane (PDMS). Subsequently, a mixture of superhydrophobic nanoscale SiO ₂ particles (SH‐SiO ₂ ), PDMS and n‐hexane solution was uniformly sprayed onto the BFS surface to enhance its hydrophobic properties. The morphology of these biomimetic surfaces was characterised using a scanning electron microscope (SEM) and ultra‐depth field microscope. The drag reduction ( DR ) performance of the biomimetic surfaces was evaluated within a Reynolds ( Re ) number range of 4.2 × 10 ⁴ –2.2 × 10 ⁵ in a circulating water tunnel. The results indicated that a drag reduction rate of 11.82% was achieved with the modified BFS at s = 300 μm and Re = 1.7 × 10 ⁵ . Additionally, the drag reduction mechanism of the modified BFS surface was analysed using the computational fluid dynamics (CFD) method. The excellent drag reduction performance was attributed to the combined effects of the ‘rolling bearing’ caused by streamwise vortices, high‐low velocity streaks and the velocity slip effect caused by hydrophobic properties at the interface. These findings offer a novel approach for creating multi‐effect coupled drag reduction surfaces.

In minimally invasive surgery, the tendency for human tissue to adhere to the electrosurgical scalpel can complicate procedures and elevate the risk of medical accidents. Consequently, the development of an electrosurgical scalpel with an anti-sticking coating is critically important. Drawing inspiration from nature, we identified that the leaves of Setaria Virids exhibit exceptional non-stick properties. Utilizing this natural surface texture as a model, we designed and fabricated a specialized anti-sticking surface for electrosurgical scalpels. Employing nanosecond laser direct writing ablation technology, we created a micro-nano textured surface on the high-frequency electrosurgical scalpel that mimics the structure found on Setaria Virids leaves. Subsequently, a TiO₂ coating was deposited onto the ablated scalpel surface via magnetron sputtering, followed by plasma-induced hydrophobic modification and treatment with octadecyltrichlorosilane (OTS) to enhance the surface’s affinity for silicone oil, thereby constructing a self-lubricating and anti-sticking surface. The spreading behavior of deionized water, absolute ethanol, and dimethyl silicone oil on this textured surface is investigated to confirm the effectiveness of the self-lubrication mechanism. Furthermore, the sticking force and quality are compared between the anti-sticking electrosurgical scalpel and a standard high-frequency electrosurgical scalpel to demonstrate the efficacy of the nanosecond laser-ablated micro-nano texture in preventing sticking. The findings indicate that the self-lubricating anti-sticking surface fabricated using this texture exhibits superior anti-sticking properties.

Improving energy efficiency and cost reduction is a perennial challenge in engineering. Natural biological systems have evolved unique functional surfaces or special physiological functions over centuries to adapt to their complex environments. Among these biological wonders, fish, one of the oldest vertebrate groups, has garnered significant attention due to its exceptional fluid dynamics capabilities. Researchers are actively exploring the potential of fish skin's distinctive structural and material characteristics in reducing resistance. In this study, models of biomimetic imbricated fish scale are established, and the evolution characteristics of the flow field and drag reduction performance on these bionic surfaces are investigated. The results showed a close relationship between the high–low velocity stripes generated and the fluid motion by the imbricated fish scale surface. The stripes' prominence increases with the spacing of the adjacent scales and tilt angle of the fish scale, and the velocity amplitude of the stripes decreases as the exposed length of the imbricated fish scale surface increases. Moreover, the biomimetic imbricated fish scale surface can decrease the velocity gradient and thereby reduce the wall shear stress. The insights gained from the fish skin‐inspired imbricated fish surface provide valuable perspectives for an in‐depth analysis of fish hydrodynamics and offer fresh inspiration for drag reduction and antifouling strategies in engineering applications.

Reducing resistance to surface friction is challenging in the field of engineering. Natural biological systems have evolved unique functional surfaces or special physiological functions to adapt to their complex environments over centuries. Among these biological wonders, fish, one of the oldest in the vertebrate group, have garnered attention due to their exceptional fluid dynamics capabilities. Fish skin has inspired innovation in reducing surface friction due to its unique structures and material properties. Herein, drawing inspiration from the unique properties of fish scales, a periodic array of fish scales was fabricated by laser ablation on a polished aluminum template. The morphology of the biomimetic fish scale surface was characterized using scanning electron microscopy and a white-light interfering profilometer. Drag reduction performance was measured in a closed circulating water tunnel. The maximum drag reduction was 10.26% at a Reynolds number of 39,532, and the drag reduction performance gradually decreased with an increase in the distance between fish scales. The mechanism of the biomimetic drag reduction surface was analyzed using computational fluid dynamics. Streamwise vortices were generated at the valley of the biomimetic fish scale, replacing sliding friction with rolling friction. These results are expected to provide a foundation for in-depth analysis of the hydrodynamic performance of fish and serve as new inspiration for drag reduction and antifouling.

For high‐speed moving objects, drag reduction has been a prolonged major challenge. To address this problem, passive and negative strategies have been proposed in the preceding decades. The integration of creatures and nature has been continuously perfected during biological evolution. Unique structure characteristics, material properties, and special functions of marine organisms can provide inexhaustible inspirations to solve this intractable problem of drag reduction. Therefore, a simple and low‐cost laser ablation method was proposed. A multi‐scale and multi‐level riblet (MSLR) surface inspired by the denticles of the sharkskin was fabricated by controlling the density of the laser path and ablation times. The morphology and topographic features were characterised using an electron microscope and a scanning white‐light interfering profilometer. Then, the drag reduction capacity of the bionic riblet surface was measured in a circulating water tunnel. Finally, the mechanism of drag reduction was analysed by the computational fluid dynamics (CFD) method. The results show that the MSLR surface has a stable drag reduction capacity with an increase in Reynold (Re) number which was contributed by high‐low velocity stripes formed on the MSLR surface. This study can provide a reference for fabricating spatial riblets with efficient drag reduction at different values of Re and improving marine antifouling.

Reduction of energy consumption and improvement of cruising speed are greatly necessary for underwater vehicles. Previously, regular riblets have been machined and the drag reduction has been verified; however, the riblet parameters are not adjusted like the denticles of sharkskin, which adapt quickly to the complex changing fluid flow. To achieve an improved drag reduction effect on the complicated shape surface, a simple, low‐cost, and timesaving stretching approach was proposed to adjust the riblet parameters on the underwater vehicle surface by controllable deformation. Nature latex rubber membrane with regular micro‐riblets was prepared as a stretching flexible film, and the spacing and height of the micro‐riblets were adjusted by adaptive control of the stretching ratio. The circulating water channel experiment verified the effectiveness and feasibility of the self‐adaptive drag reduction by the controllable deformation method. The results demonstrated that the drag reduction rate of the controllable deformation bionic fish skin was 4.26% compared with a smooth surface at 0.25 m/s with an angle of attack of 0°, which is better than any other angle. The controllable deformation bionic fish skin provides a feasible method for the drag reduction of complex surface adaptive underwater vehicles.