Small Structure, Large Effect: Functional Surfaces Inspired by Salvinia Leaves

Abstract

Nature‐inspired superhydrophobic surfaces have attracted significant attention because of their remarkable properties. In particular, recent findings about the aquatic plant Salvinia provide novel approaches for the application of superhydrophobic surfaces. The unique heterogeneous eggbeater structures endow Salvinia leaves with superhydrophobicity and strong adhesion, which ensures that the leaves show durable air‐retainability in underwater environments. However, the complex eggbeater structures present a difficult manufacturing challenge. Therefore, this review first introduces the air‐retention mechanism, which may benefit the design of Salvinia‐inspired structures. Moreover, advanced techniques including photolithography, direct laser lithography, chemical vapor deposition, electrodeposition, electrostatic flocking, 3D printing, chemical etching, and plasma etching recently have been developed for fabricating Salvinia‐inspired structures. This review focuses on the advantages, disadvantages, and application prospects of such techniques. In addition, the excellent air‐retainability of Salvinia structures has inspired many engineering applications, including drag reduction; water harvesting, evaporation, and repellence; oil/water separation; and thermal insulation. This review discusses the performance and challenges of artificial structures to such applications. Finally, methods of evaluating air‐retainability are discussed. It is expected that this review will not only satisfy scientific curiosity but also contribute to the design and application of Salvinia‐inspired functional surfaces.

Bimodal Tactile Sensor without Signal Fusion for User-Interactive Applications

“…Mimicry of the human skin represents an emerging and promising direction toward the implementation of humanoid robotics, biomimetic prosthetics, and artificial intelligence. − In the last decades, many endeavors have been dedicated to augmenting artificial skin with mechanical and thermal sensing abilities, with emphasis on the development of multifunctional materials responsive to multiple stimuli or the arranged integration of various sensory units into a hybrid system. − For example, organic semiconductors combined with a transistor , or capacitor structure were identified for a large-scale matrix of pressure and thermal sensors; carbon nanomaterials (carbon nanotubes, graphene, etc. ) with forms of yarn, , sponge, − and microstructures − were developed for flexible sensing of pressure and temperature; metal percolation or mesh was patterned into a transparent panel with pressure and temperature sensing; , ferroelectric composites with a designed interlock construction demonstrated the enhanced or self-powered sensing of pressure and temperature; − hydrogels with conductive fillers were proposed for self-healing and sensing of pressure and temperature; , and individual pressure and temperature sensory pixels connected with serpentine electrodes were applied to create a stretchable array for multifunctional sensing . Despite the thriving progress, these bimodal sensors produce signals responsive to temperature and pressure that are similar, such as relative changes in resistance, capacitance, voltage, or current.…”

Temperature-Responsive, Femtosecond Laser-Ablated Ceramic Surfaces with Switchable Wettability for On-Demand Droplet Transfer

“…Bioinspired superhydrophobic surfaces have attracted considerable attention due to their widespread applications in droplet manipulation, 1−4 oil/water separation, 5,6 friction reduction and wear resistance, 7,8 and so on. 9,10 Various methods have been developed to fabricate such surfaces, 11 such as laser processing, 12,13 etching, 14,15 three-dimensional (3D) printing, 16,17 and self-assembly. 18,19 Because of the advantages of high precision and low thermal effects, ultrafast lasers are often used to prepare such surfaces on metal, 20,21 ceramic, 22 and polymer substrates.…”

Robust Underwater Air Layer Retention and Restoration on Salvinia-Inspired Self-Grown Heterogeneous Architectures

“…From the view of fabrication, the fantastic combination of hierarchical structures with such heterogeneous super-hydrophobic surfaces and hydrophilic apexes makes the artificial reproduction of Salvinia -inspired microstructures a great challenge. Most of the previous studies mimicked either only the physical structure or chemical property, which limited their applications . (1) Tricinci et al fabricated hollow microstructures 100 repetitions smaller than those of natural Salvinia by direct laser lithography .…”

“…Most of the previous studies mimicked either only the physical structure or chemical property, which limited their applications. 20 (1) Tricinci et al fabricated hollow microstructures 100 repetitions smaller than those of natural Salvinia by direct laser lithography. 21 Applications in underwater hydrophobicity and localized water vapor condensation were studied.…”