Multi-biomimetic Double Interlaced Wetting Janus Surface for Efficient Fog Collection.

Various methods to solve water scarcity have attracted increasing attention. However, most existing water harvesting schemes have a high demand for preparation methods and costs. Here, a multi-biomimetic double interlaced wetting Janus surface (DIWJS) was prepared by laser for effective fog collection. The as-prepared surfaces are composed of superhydrophilic points/hydrophobic substrates on the A-side and superhydrophilic stripes/hydrophobic substrates on the B-side. The interlaced wettability and superhydrophilic points on the A side are conducive to capture and permeation of droplets. The superhydrophilic stripes and interlaced wettability on the B-side are conducive to transportation and shedding of droplets. Therefore, the overall fog collection process is accelerated. The proposal of smart farm model validates broad application prospects of DIWJS. This work provides an advanced and multi-biomimetic surface and provides important insights for green, low-cost, and versatile strategies to solve water scarcity issues.

Droplet Bottom Expansion and Its Wettability Control Mechanism Based on Macroscopic Defects.

Biomimetic surfaces with special wettability have received much attention due to their promising prospects in droplet manipulation. Although some progress has been made, the manipulation of droplets by macroscopic defects of the millimeter structure and the wetting-state transition mechanism have rarely been reported. Herein, inspired by lotus leaves and desert beetles, biomimetic surfaces with macroscopic defects are prepared by laser processing and chemical modification. Various functions of droplet manipulation are achieved by controlling the millimeter-scale macroscopic defects, such as droplet capture, motion trajectory changing, and liquid well. And a droplet bottom expansion phenomenon is proposed: wetting-state transition in superhydrophobic regions around defects. The "edge failure effect" is proposed to explain the force analysis of droplet capture and the droplet bottom expansion to distinguish it from the adhesion phenomenon presented by the droplet sliding. 53.28° is defined as the expanded saturated angle of the as-prepared surface, which is used to distinguish whether the defect could cause the droplet bottom expansion. An enhanced edge failure effect experiment is designed to make the droplet bottom expansion more intuitive. This work provides a mechanistic explanation of the surfaces that utilize macroscopic defects for droplet manipulation. It can be applied to the monitoring of droplet storage limits, providing a perspective on the design and optimization of superhydrophobic surfaces with droplet manipulation.

Bioinspired Photoelectronic Synergy Coating with Antifogging and Antibacterial Properties.

Optically transparent glass with antifogging and antibacterial properties is in high demand for endoscopes, goggles, and medical display equipment. However, many of the previously reported coatings have limitations in terms of long-term antifogging and efficient antibacterial properties, environmental friendliness, and versatility. In this study, inspired by catfish and sphagnum moss, a novel photoelectronic synergy antifogging and antibacterial coating was prepared by cross-linking polyethylenimine-modified titanium dioxide (PEI-TiO2), polyvinylpyrrolidone (PVP), and poly(acrylic acid) (PAA). The as-prepared coating could remain fog-free under hot steam for more than 40 min. The experimental results indicate that the long-term antifogging properties are due to the water absorption and spreading characteristics. Moreover, the organic-inorganic hybrid of PEI and TiO2 was first applied to enhance the antibacterial performance. The Staphylococcus aureus and the Escherichia coli growth inhibition rates of the as-prepared coating reached 97 and 96% respectively. A photoelectronic synergy antifogging and antibacterial mechanism based on the positive electrical and photocatalytic properties of PEI-TiO2 was proposed. This investigation provides insight into designing multifunctional bioinspired surface materials to realize antifogging and antibacterial that can be applied to medicine and daily lives.

Switchable Wettability Surface with Chemical Stability and Antifouling Properties for Controllable Oil-Water Separation.

Membrane materials with special wettability for separating oil-water mixtures have gradually become one of the research hotspots. However, oily wastewater usually has very strong corrosiveness, which puts forward high requirements for the chemical stability of the separation membrane. In addition, oil droplets may block the pores, resulting in the decrease of separation efficiency or even separation failure. Herein, biomimetic TiO2-titanium meshes (BTTMs) with switchable wettability were successfully fabricated by one-step dip coating of poly(vinylidene difluoride) and modified TiO2 suspension on the titanium meshes. The simple and efficient preparation method will facilitate the promotion of this smart material. Due to the controlled wettability, the BTTM can separate water or oil from an oil-water mixture as required. When the BTTM was immersed in strong corrosive solution or liquid nitrogen, the wettability did not change much, showing the good stability of the BTTM. Furthermore, the BTTM also has self-healing ability, self-recovery anti-oil-fouling properties, and self-cleaning behavior, which help it resist oil pollution and improve its recyclability. This study provides a simple and efficient strategy for fabricating a stable smart surface for on-demand controllable treatment of corrosive oily wastewater.

What Exactly Can Bionic Strategies Achieve for Flexible Sensors?

Flexible sensors have attracted great attention in the field of wearable electronic devices due to their deformability, lightness, and versatility. However, property improvement remains a key challenge. Fortunately, natural organisms exhibit many unique response mechanisms to various stimuli, and the corresponding structures and compositions provide advanced design ideas for the development of flexible sensors. Therefore, this Review highlights recent advances in sensing performance and functional characteristics of flexible sensors from the perspective of bionics for the first time. First, the "twins" of bionics and flexible sensors are introduced. Second, the enhancements in electrical and mechanical performance through bionic strategies are summarized according to the prototypes of humans, plants, and animals. Third, the functional characteristics of bionic strategies for flexible sensors are discussed in detail, including self-healing, color-changing, tangential force, strain redistribution, and interfacial resistance. Finally, we summarize the challenges and development trends of bioinspired flexible sensors. This Review aims to deepen the understanding of bionic strategies and provide innovative ideas and references for the design and manufacture of next-generation flexible sensors.

Microstructure and Properties of CoCrNi/Nano-TiC/Micro-TiB2 Composite Coatings Prepared via Laser Cladding.

Laser cladding was used to prepare CoCrNi-xTiC-xTiB2 (x = 0, 5, 15 wt.%) composite coatings on 316L stainless steel. Then, ceramic mass fraction effects on the microstructure and properties were investigated. Results show viable metallurgical bonding between the coating and the substrate, with no apparent pores or cracks. The addition of ceramics transformed the coating phase from a single-phase face-centered cubic (FCC) to a multi-phase FCC+TiC+TiB2. TiC and TiB2 increased the hardness of the CoCrNi-xTiC-xTiB2 coating from 209.71 HV to 494.77 HV by grain refinement and diffusion strengthening. The substrate wear loss was 0.0088 g, whereas the CoCrNi-xTiC-xTiB2 (x = 15%) coating wear loss was only 0.0012 g. Moreover, the overall wear mechanism of the coating was changed: the substrate wear mechanism was used for abrasive wear, adhesive wear and fatigue wear, and the coating with the addition of 15 wt.% nano-TiC and 15 wt.% micro-TiB2 was the wear mechanism for pitting fatigue wear.

A biomimetic surface with switchable contact angle and adhesion for transfer and storage of microdroplets.

Recently, superhydrophobic surfaces with switchable wettability have attracted much attention. The ability to control the contact angle and adhesion of the multifunctional smart surface will be more beneficial to meet the complex practical applications, but until now this has been a challenge. Inspired by rose petals, we report a smart, biomimetic, and superhydrophobic surface whose wettability can switch reversibly between superhydrophobicity and superhydrophilicity on the Cu substance. At the same time, we can control the adhesion on the as-prepared superhydrophobic surface by covering and removing the ink. Thus, the as-prepared surface can be used as a medium for microdroplet transfer and storage. Compared with the original Cu substrate, electrochemical measurements show that the corrosion inhibition of the superhydrophobic surface is significantly improved. Good corrosion resistance allows the platform to be used to manipulate or store more types of microdroplets, especially corrosive microdroplets. In addition, the as-prepared surface has a good stability which facilitates the practical application of the as-prepared smart surface. This work provides a smart and effective strategy for lossless transfer and patterned storage of microdroplets. It is also promising for the design of new smart interface materials such as for biological cell manipulation, chemical microreaction and other types of microfluidic devices.