Sunflower-Inspired Superhydrophobic Surface with Composite Structured Microcone Array for Anisotropy Liquid/Ice Manipulation.

Precisely controlling the directional motion trajectories of droplets on anisotropic 3D functional surfaces has great application potential in self-cleaning, drug delivery, and droplet power generation, but it also faces huge challenges. Herein, inspired by the microcone structure in the heart of sunflowers, a nanoneedle-modified microcone array surface (NMAS) is reported. The surface is created using a combination of nanosecond laser direct engraving and electroforming and is subsequently fluorinated. Through programmable control of the laser spot, the geometric parameters and inclination angle of the microcone can be quickly and finely adjusted, thereby achieving precise control of the droplet bouncing trajectory. The results show that droplets can achieve programmable multiple bouncing behaviors on patterned functional surfaces, including gravity-defying hopping and directional water transport. It is worth noting that this functional surface has delayed freezing and anti-freezing effects. Furthermore, this functional surface has a wide range of potential applications, including surface self-cleaning, droplet capture, and droplet-based chemical microreactions, especially in the field of anti-icing operations. This opens up a new way for the directional transport of droplets on biomimetic functional surfaces.

A Transparent Photo/Electrothermal Composite Coating with Liquid-like Slippery Property for All-Day Anti-/De-Icing.

A photo/electrothermal surface can convert sunlight and electricity into heat to solve icing problems. The combination of active photo/electrothermal surfaces with passive slippery surfaces provides a highly efficient strategy for all-day anti/deicing. However, the lack of transparency remains a primary impediment to the widespread application of these anti-icing measures in photovoltaics, windshields, and other fields. Herein, we report a bilayer transparent photo/electrothermal coating with a liquid-like slippery property for all-day anti/deicing. The prepared coating exhibits ultraslippery, low ice adhesion, and enhanced stability properties through covalent grafting of polydimethylsiloxane (PDMS) brushes in a cross-linked skeleton of epoxy. Moreover, the coating demonstrates a visible transmittance of up to 77% and effectively absorbs ultraviolet and near-infrared light due to the addition of ultraviolet and infrared absorbers, resulting in a temperature increase under sun illumination. The bottom indium tin oxide layer is fabricated to provide the composite coating with electrothermal capability, so that it can achieve all-weather deicing. The coupling of photo/electrothermal and slippery properties can promote the rapid removal of grown ice in a short time. The slippery properties and their exceptional durability under mechanical, optical, and thermal conditions render the composite coatings highly promising for engineering applications.

A New Composite Material with Energy Storage, Electro/Photo-Thermal and Robust Super-Hydrophobic Properties for High-Efficiency Anti-Icing/De-Icing.

All weather, high-efficiency, energy-saving anti-icing/de-icing materials are of great importance for solving the problem of ice accumulation on outdoor equipment surfaces. In this study, a composite material with energy storage, active electro-/photo-thermal de-icing and passive super-hydrophobic anti-icing properties is proposed. Fluorinated epoxy resin and MWCNTs/PTFE particles are used to prepare the top multifunctional anti-icing/de-icing layer, which exhibited super-hydrophobicity with water contact angle greater than 155° and conductivity higher than 69 S m-1. The super-hydrophobic durability of the top layer is verified through tape peeling and sandpaper abrasion tests. The surface can be heated by applying on voltage or light illumination, showing efficient electro-/photo-thermal and all-day anti-icing/de-icing performance. The oleogel material at the bottom layer is capable to absorb energy during heating process and release it during cooling process by phase transition, which greatly delayed the freezing time and saved energy. The icing test of single ice droplet, electro-/photo-thermal de-icing and defrosting tests also proved the high efficiency and energy saving of the anti-icing/de-icing strategy. This study provided a new way to manufacture multi-functional materials for practical anti-icing/de-icing applications.

Recent progress on the development of bioinspired surfaces with high aspect ratio microarray structures: From fabrication to applications.

Surfaces with high aspect ratio microarray structures can implement sophisticated assignment in typical fields including microfluidics, sensor, biomedicine, et al. via regulating their deformation or the material properties. Inspired by natural materials and systems, for example sea cockroaches, water spiders, cacti, lotus leaves, rice leaves, and cedar leaves, many researchers have focused on microneedle functional surface studies. When the surface with high aspect ratio microarray structures is stimulated by the external fields, such as optical, electric, thermal, magnetic, the high aspect ratio microarray structures can undergo hydrophilic and hydrophobic switching or shape change, which may be gifted the surfaces with the ability to perform complex task, including directional liquid/air transport, targeted drug delivery, microfluidic chip sensing. In this review, the fabrication principles of various surfaces with high aspect ratio microarray structures are classified and summarized. Mechanisms of liquid manipulation on hydrophilic/hydrophobic surfaces with high aspect ratio microarray structures are clarified based on Wenzel model, Cassie model, Laplace pressure theories and so on. Then the intelligent control strategies have been demonstrated. The applications in microfluidic, drug delivery, patch sensors have been discussed. Finally, current challenges and new insights of future prospects for dynamic manipulation of liquid/air based on biomimetic surface with high aspect ratio microarray structures are also addressed.

High-Efficient Microdroplet Harvesting and Detaching Inspired from Sarracenia Lid Trichome.

Fog harvesting plays a pivotal role in harnessing atmospheric water resources and holds significant promise for alleviating global water scarcity. Nonetheless, enhancing harvesting efficiency remains a persistent challenge, especially concerning the rapid detachment of droplets from surfaces. In this study, we discovered that the trichomes of Sarracenia not only efficiently harvest and transport liquid but also quickly drain harvested liquid. We have elucidated the augmentation mechanism behind effective fog harvesting and drainage within the lid of Sarracenia. The trichomes facing the counterflow can enhance fog harvesting efficiency by 80% through air-flow-assisted spreading of liquid film. The wedge corner generated by the interface between hydrophilic and hydrophobic surfaces, coupled with the reduction of cross-sectional angles, diminishes the adhesive force of liquid droplets, fosters droplet spheroidization, and substantially facilitates droplet detachment. In addition, the quantitative detachment of droplets can be achieved by adjusting the cross-sectional angle and wetting gradient. This integrated structure combining efficient condensation and detachment has diverse applications in cooling towers and seawater desalination.

High-Efficient Fog Harvest from a Synergistic Effect of Coupling Hierarchical Structures.

Fog harvesting is an important method to solve the water shortage in arid and semi-arid areas by collecting water from air. Improving fog harvesting efficiency is still a big challenge to be overcome. Herein, under the inspiration of natural creatures, a novel harvesting structure that couples a hierarchical microchannel (HMC) needle with the Janus membrane by taking a conical pore as their junction is proposed. Such an HMC-conical pore-Janus membrane system can improve the harvesting efficiency by regulation of liquid behavior in the whole fog harvesting process involving droplet capture from air, high speed transport on the microchannel, and droplet detachment from Janus. The synergistic effects of the hierarchical channel-conical pore-Janus structure are exploited in terms of capture, transport, and detachment capabilities, and their underlying mechanism to enhance fog harvesting efficiency is built. Compared with the traditional harvesting structure, the proposed hierarchical channel-conical-Janus coupling mode was demonstrated to improve fog harvesting efficiency by 90%. Such a coupled system has potential applications in efficient fog harvesting systems, microfluidic devices, and liquid manipulation.

Highly Efficient Multiscale Fog Collector Inspired by Sarracenia Trichome Hierarchical Structure.

Fog harvesting through bionic strategies to solve water shortage has drawn considerable attention. Recently, an ultrafast fog harvesting and transport mode was identified in Sarracenia trichome, which is mainly attributed to its superslippery capillary force induced by its unique hierarchical microchannel. However, the underlying effect of hierarchical microchannel-induced ultrafast transport on fog harvesting and the multiscale structural coupling effect on highly efficient fog harvesting are still great challenges. Herein, a bionic Sarracenia trichome (BST) with an on-demand regular hierarchical microchannel is designed using a one-step thermoplastic stretching approach on a glass fiber bundle. The BST is engineered to harbor major channels confined by an inner gear pattern along with junior microchannels that are automatically assembled by the glass fiber monofilaments. The BST shows enhanced capillary condensation and fog harvesting performance, in part due to its coupling effect with a Janus membrane (JM). Hence, a highly efficient multiscale fog collector is developed, in which a gradient high-pressure field is purposely formed to improve by threefold fog harvesting performance compared with a single-scale structure. This easy manufacturing and low-cost fog collector may represent a useful tool for harvesting fog water for production and living and pave the way for further investigations.