Bio-inspired titanium dioxide materials with special wettability and their applications

Titanium dioxide (TiO2) is one of the most widely used nanomaterials in our daily life. In 1972, Fujishima and Honda reported the photo electrolysis of water into H2 and O2 utilizing an electrochemical cell in which the TiO2 single-crystal electrode is connected with a Pt electrode. This is analogus with the natural photosynthesis that produces oxygen through oxidizing water and reducing carbon dioxide using sunlight, where solar energy is converted into chemical energy. Since that time, photocatalysis has received considerable attention owing to its important applications in the conversion of light energy into useful chemical energy. In 1997, Fujishima et al. first reported the photogeneration of a superamphiphilic (both superhydrophilic and superoleophilic, where the contact angle of water and oil on a surface is almost 0°, respectively) TiO2 surface under UV light irradiation, showing self-cleaning and antifogging characteristics. This breakthrough work expanded the research field of TiO2 materials and marked the beginning of a new era in TiO2-based self-cleaning materials. Since then, an important effort has been focused on the understanding of the fundamental mechanism of this novel function and on the development of selfcleaning materials for a wide range of applications in energy, environmental, and industrial fields, resulting in the generation of new markets. Although photocatalysis and photoinduced superhydrophilicity can take place simultaneously on the same TiO2 surface, they are intrinsically different processes. In recent years, environmental pollution and damage on a global scale have emerged as a serious issue. The viable environmental cleanup has attracted a great deal of attention to achieve important breakthroughs in the design of advanced materials and in the development of new technology. Now, a variety of TiO2-based materials have been commercialized arising from their unique photoinduced properties. Furthermore, these commercial products demonstrate their importance in the environmental cleanup

Programmable droplet transport on multi-bioinspired slippery surface with tridirectionally anisotropic wettability

Directional droplet transport on functional surfaces with anisotropic wettability has shown great potential applications in various fields such as water harvesting, chemical micro-reaction, and biomedical analysis. However, the in-plane manipulation of the anisotropic droplet motion in more than two directions is still a challenge. Herein, through the fusion of inspirations from rice leaves, butterfly wings and Pitcher plants, we report a tridirectionally anisotropic slippery surface (TASS) with periodic step-like micro grooves for programmable droplet transport. TASS possesses a tridirectional droplet sliding behavior, i.e., the ultra-slipperiness along the grooves with a sliding angle of ∼ 2°, and the bidirectionally anisotropic sliding perpendicular to the grooves with sliding angle difference up to ∼ 50°, which is caused by the pinning effect of the step edge. Under the assistance of periodic vertical vibration, groove-features and droplet-volume dependent unidirectional droplets transports are realized on horizontally placed TASS, based on which two micro-reactors are designed to control the sequence of droplets merging and subsequent chemical reactions. Additionally, by utilizing the slipperiness (i.e., ultra-low sliding angle for liquid droplet) along the grooves simultaneously, programmable droplet transport under vertical vibration is further demonstrated on a tilted TASS. This work will provide a new avenue for the understanding of anisotropic wettability on asymmetric slippery surface, and thus offer a great opportunity to develop advanced interface for multidirectional droplet transport, chemical micro-reactor, etc

On-Chip Liquid Manipulation via a Flexible Dual-Layered Channel Possessing Hydrophilic/Hydrophobic Dichotomy

The hydrophilic/hydrophobic cooperative interface provides a smart platform to control liquid distribution and delivery. Through the fusion of flexibility and complex structure, we present a manipulable, open, and dual-layered liquid channel (MODLC) for on-demand mechanical control of fluid delivery. Driven by anisotropic Laplace pressure, the mechano-controllable asymmetric channel of MODLC can propel the directional slipping of liquid located between the paired tracks. Upon a single press, the longest transport distance can reach 10 cm with an average speed of ∼3 cm/s. The liquid on the MODLC can be immediately manipulated by pressing or dragging processes, and versatile liquid-manipulating processes on hierarchical MODLC chips have been achieved, including remote droplet magneto-control, continuous liquid distributor, and gas-producing chip. The flexible hydrophilic/hydrophobic interface and its assembly can extend the function and applications of the wettability-patterned interface, which should update our understanding of complex systems for sophisticated liquid transport

On-Chip Liquid Manipulation via a Flexible Dual-Layered Channel Possessing Hydrophilic/Hydrophobic Dichotomy

The hydrophilic/hydrophobic cooperative interface provides a smart platform to control liquid distribution and delivery. Through the fusion of flexibility and complex structure, we present a manipulable, open, and dual-layered liquid channel (MODLC) for on-demand mechanical control of fluid delivery. Driven by anisotropic Laplace pressure, the mechano-controllable asymmetric channel of MODLC can propel the directional slipping of liquid located between the paired tracks. Upon a single press, the longest transport distance can reach 10 cm with an average speed of ∼3 cm/s. The liquid on the MODLC can be immediately manipulated by pressing or dragging processes, and versatile liquid-manipulating processes on hierarchical MODLC chips have been achieved, including remote droplet magneto-control, continuous liquid distributor, and gas-producing chip. The flexible hydrophilic/hydrophobic interface and its assembly can extend the function and applications of the wettability-patterned interface, which should update our understanding of complex systems for sophisticated liquid transport

Floatable, Self-Cleaning, and Carbon-Black-Based Superhydrophobic Gauze for the Solar Evaporation Enhancement at the Air–Water Interface

Efficient solar evaporation plays an indispensable role in nature as well as the industry process. However, the traditional evaporation process depends on the total temperature increase of bulk water. Recently, localized heating at the air–water interface has been demonstrated as a potential strategy for the improvement of solar evaporation. Here, we show that the carbon-black-based superhydrophobic gauze was able to float on the surface of water and selectively heat the surface water under irradiation, resulting in an enhanced evaporation rate. The fabrication process of the superhydrophobic black gauze was low-cost, scalable, and easy-to-prepare. Control experiments were conducted under different light intensities, and the results proved that the floating black gauze achieved an evaporation rate 2–3 times higher than that of the traditional process. A higher temperature of the surface water was observed in the floating gauze group, revealing a main reason for the evaporation enhancement. Furthermore, the self-cleaning ability of the superhydrophobic black gauze enabled a convenient recycling and reusing process toward practical application. The present material may open a new avenue for application of the superhydrophobic substrate and meet extensive requirements in the fields related to solar evaporation

On-Chip Liquid Manipulation via a Flexible Dual-Layered Channel Possessing Hydrophilic/Hydrophobic Dichotomy

The hydrophilic/hydrophobic cooperative interface provides a smart platform to control liquid distribution and delivery. Through the fusion of flexibility and complex structure, we present a manipulable, open, and dual-layered liquid channel (MODLC) for on-demand mechanical control of fluid delivery. Driven by anisotropic Laplace pressure, the mechano-controllable asymmetric channel of MODLC can propel the directional slipping of liquid located between the paired tracks. Upon a single press, the longest transport distance can reach 10 cm with an average speed of ∼3 cm/s. The liquid on the MODLC can be immediately manipulated by pressing or dragging processes, and versatile liquid-manipulating processes on hierarchical MODLC chips have been achieved, including remote droplet magneto-control, continuous liquid distributor, and gas-producing chip. The flexible hydrophilic/hydrophobic interface and its assembly can extend the function and applications of the wettability-patterned interface, which should update our understanding of complex systems for sophisticated liquid transport

On-Chip Liquid Manipulation via a Flexible Dual-Layered Channel Possessing Hydrophilic/Hydrophobic Dichotomy

The hydrophilic/hydrophobic cooperative interface provides a smart platform to control liquid distribution and delivery. Through the fusion of flexibility and complex structure, we present a manipulable, open, and dual-layered liquid channel (MODLC) for on-demand mechanical control of fluid delivery. Driven by anisotropic Laplace pressure, the mechano-controllable asymmetric channel of MODLC can propel the directional slipping of liquid located between the paired tracks. Upon a single press, the longest transport distance can reach 10 cm with an average speed of ∼3 cm/s. The liquid on the MODLC can be immediately manipulated by pressing or dragging processes, and versatile liquid-manipulating processes on hierarchical MODLC chips have been achieved, including remote droplet magneto-control, continuous liquid distributor, and gas-producing chip. The flexible hydrophilic/hydrophobic interface and its assembly can extend the function and applications of the wettability-patterned interface, which should update our understanding of complex systems for sophisticated liquid transport

On-Chip Liquid Manipulation via a Flexible Dual-Layered Channel Possessing Hydrophilic/Hydrophobic Dichotomy

The hydrophilic/hydrophobic cooperative interface provides a smart platform to control liquid distribution and delivery. Through the fusion of flexibility and complex structure, we present a manipulable, open, and dual-layered liquid channel (MODLC) for on-demand mechanical control of fluid delivery. Driven by anisotropic Laplace pressure, the mechano-controllable asymmetric channel of MODLC can propel the directional slipping of liquid located between the paired tracks. Upon a single press, the longest transport distance can reach 10 cm with an average speed of ∼3 cm/s. The liquid on the MODLC can be immediately manipulated by pressing or dragging processes, and versatile liquid-manipulating processes on hierarchical MODLC chips have been achieved, including remote droplet magneto-control, continuous liquid distributor, and gas-producing chip. The flexible hydrophilic/hydrophobic interface and its assembly can extend the function and applications of the wettability-patterned interface, which should update our understanding of complex systems for sophisticated liquid transport

On-Chip Liquid Manipulation via a Flexible Dual-Layered Channel Possessing Hydrophilic/Hydrophobic Dichotomy

The hydrophilic/hydrophobic cooperative interface provides a smart platform to control liquid distribution and delivery. Through the fusion of flexibility and complex structure, we present a manipulable, open, and dual-layered liquid channel (MODLC) for on-demand mechanical control of fluid delivery. Driven by anisotropic Laplace pressure, the mechano-controllable asymmetric channel of MODLC can propel the directional slipping of liquid located between the paired tracks. Upon a single press, the longest transport distance can reach 10 cm with an average speed of ∼3 cm/s. The liquid on the MODLC can be immediately manipulated by pressing or dragging processes, and versatile liquid-manipulating processes on hierarchical MODLC chips have been achieved, including remote droplet magneto-control, continuous liquid distributor, and gas-producing chip. The flexible hydrophilic/hydrophobic interface and its assembly can extend the function and applications of the wettability-patterned interface, which should update our understanding of complex systems for sophisticated liquid transport