In recent years, there have been a lot of studies on hydrophobic / oleophobic materials, but adhesion has not received much attention as an important aspect of the physical properties of the surface of the material. In particular, there has not been much experimental research on how to adjust the adhesion of the surface of the material.
The Research Group of Material Surface and Interface Behavior of Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences is devoted to the research work of material surface adhesion behavior and has made a series of progress.
The research team first used polymer materials to successfully prepare a super-hydrophobic / oleophobic coating material with a complex micro / nano binary structure and depth distribution. By changing the content of the hydrophilic component in the hydrophobic coating, the water droplets in the Regulation of adhesion on the surface. Next, the research team constructed an ordered array of titanium dioxide nanotubes on the titanium surface of the engineering material using anodization, and successfully realized the rapid reversible conversion of surface water droplets and oil droplets adhesion-sliding by ultraviolet light irradiation and heat treatment. Later, the group proposed a new method to achieve reversible regulation of surface adhesion behavior using graft-responsive polymer brushes. This method can realize the reversible conversion of water droplets between surface adhesion and sliding under different environmental stimuli.
In response to the effect of light irradiation induction on changes in wetting properties, the team successfully achieved reversible control of the fluidity of water droplets using a light-responsive coating on a rough surface. The surface coating is composed of an amino silicone oil as an alkaline hydrophobic material and an embedded azo compound as a photosensitive medium, and the azo compound exhibits trans / cis conformation changes under visible / ultraviolet light irradiation. When the azo compound assumes trans and cis conformations, the surface transitions between the wet state and the sticky state, but the surface's hydrophobicity does not change significantly.
The researchers propose that the wetting properties conversion and hysteresis are closely related to the molecular-level surface composition. The researchers investigated the dynamic wetting properties of compressed water droplets on anodized aluminum modified with responsive polymer brushes. The results show that the graft-responsive polymer diluted on the surface does not significantly change the wetting properties of the surface, but it leads to the conversion and hysteresis of the surface-responsive wetting properties. When the water droplet interacts with the polymer and becomes a hydrate, the wetting performance can be easily converted from the Cassie mode to the Wenzel mode, showing high hysteresis and reduced contact angle. If the water drops do not interact with the polymer, the water drops are in a stable Cassie wetting mode.
This work is very important for understanding the wetting theory, and is of great significance for the design of smart surfaces, such as microfluidic devices. In addition, the above research work is of great significance in engineering fields such as microfluid lossless transportation, smart coating, self-cleaning surface and sealing protection.
Relevant research has been supported by the "Hundred Talents Program" project of the Chinese Academy of Sciences, the National Key Basic Research and Development Program, the National Natural Science Foundation of China and the National Key Research Project. The research results were published in J. Phys. Chem. C (2010, 114, 9938–9944), Chem. Comm., (2009, 7018–7020) Soft Matter (2009, 5, 3097–3105; 2011, 7, 515– 523; 2011, 7, 3331–3336;) and Langmuir (2010, 26 (14), 12377–12382).
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