Quartic coupling and its effect on wetting behaviors in nematic liquid crystals

Based on the fact that rubbed groove patterns also affect the anchoring of liquid crystals at substrates,a quartic coupling is included in constructing the surface energy for a liquid crystal cell.The phase diagram and the wetting behaviors of the liquid crystal cell,bounded by surfactant-laden interfaces in a magnetic field perpendicular to the substrate are discussed by taking the quartic coupling into account.The nematic order increases at the surface while it decreases in the bulk as a result of the introduction of quartic substrate-liquid crystal coupling,indicating that the groove anchoring makes the liquid crystal molecules align more orderly near the substrate than away from it.This causes a different wetting behavior：complete wetting.

Effect of Substrate-Water Interaction on the Wetting Behavior in Water-Oil and Substrate-Water-Oil Systems

The effects of the substrate-water interaction on the wetting behavior in water-oil and surfactant-water-oil systems confined by one substrate which has the preferential interaction to one species of particles have been investigated by using the free energy analysis and discontinuous molecular dynamic simulations. As the preferential interaction between the substrate and water particles varies from small repulsion to large attraction, the partial drying, partial wetting and complete wetting state are observed in sequence. In addition, the wetting behavior of surfactant aqueous solution on the substrate is not only dependent on the interaction, but also limited by the maximum equilibrium concentration of surfactants at the interface.

Influence of PVD-duplex-treated, Bionic Surface Structures on the Wetting Behavior for Sheet-Bulk Metal Forming Tools

Bionic surface structures, inspired by the flora, were developed for Sheet-Bulk Metal Forming （SBMF） in order to locally control the friction condition by adjusting the wetting behavior. Five bionic structures were micromilled on ASP 2023 in annealed as well as hardened and tempered conditions. Subsequently, the structured surfaces were plasma-nitrided and coated with a CrA1N thin film. The influence of the treatment method on the structural geometry was investigated with the aid of a scanning electron microscope and 3D-profilometer. The wetting behaviors of water and deep drawing oil （Berufluid ST6007） on bionic surfaces were evaluated using contact angle measurements. The resulting micro-milled structures exhibit an almost identical shape as their bionic models. However, the roughness of the structured surfaces is influenced by the microstructure. The combination of plasma-nitriding and Physical Vapor Deposition （PVD） leads to an increase in roughness. All bionic struc- tures possess higher contact angles than that of the unstructured surfaces when wetted by water. This can be explained by the fact that the structural elevations block the spreading. When the bionic surfaces are wetted by deep drawing oil, the lubricant spreads in the structural cavities, leading to smaller contact angles. Furthermore, the anisotropy of the structure has an influence on the wetting behavior.

Gradient Wetting Transition from the Wenzel to Robust Cassie-Baxter States along Nanopillared Cicada Wing and Underlying Mechanism

Gradient wettability is important for some living organisms.Herein,the dynamic responses of water droplets impacting on the surfaces of four regions along the wing vein of cicada Cryptotympana atratafabricius are investigated.It is revealed that a gradient wetting behavior from hydrophilicity(the Wenzel state)to hydrophobicity and further to superhydrophobicity(the Cassie-Baxter state)appears from the foot to apex of the wing.Water droplets impacting on the hydrophilic region of the wing cannot rebound,whereas those impacting on the hydrophobic region can retract and completely rebound.The hydrophobic region exhibits robust water-repelling performance during the dynamic droplet impact.Moreover,a droplet sitting on the hydrophobic region can recover its spherical shape after squeezed to a water film as thin as 0.45 mm,and lossless droplet transportation can be achieved at the region.Based on the geometric parameters of the nanopillars at the hydrophilic and hydrophobic regions on the cicada wing,two wetting models are developed for elucidating the mechanism for the gradient wetting behavior.This work directs the design and fabrication of surfaces with gradient wetting behavior by mimicking the nanopillars on cicada wing surface.

From Self-assembled Monolayers to Chemically Patterned Brushes:Controlling the Orientation of Block Copolymer Domains in Films by Substrate Modification

Block copolymer lithography is emerging as one of the leading technologies for patteming nanoscale dense features. In almost all potential applications of this technology, control over the orientation of cylindrical and lamellar domains is required for pattern transfer from the block copolymer film. This review highlights the state-of-art development of brushes to modify the substrates to control the assembly behaviors of block copolymers in films. Selected important contributions to the development of self-assembled monolayers, polymer brushes and mats, and chemically patterned brushes are discussed.

Structure design and property of multiple-basis-element(MBE)alloys flexible films

A controlled wrinkled structure is a simple and effective approach to achieve unique properties and has been widely used in flexible materials.In this study,we reported a substrate prestrain method for fabricating wrinkle-structured Zr52Ti34Nb14 multiplebasis-element(MBE)alloy films as biocompatible materials.Variations in the film thickness and substrate prestraining enabled a precise control of the amplitude and wavelength of the wrinkled structures,ranging from micrometers to nanometers.Moreover,owing to the flexibility of the wrinkled structures,the wrinkle-structure pattern could be adjusted by simply relaxing or further stretching of the substrate,leading to dynamically tunable transmittance and wetting behaviors.This result not only reveals Zr52Ti34Nb14 MBE alloy films as a potential flexible material,but also provides a new structural design approach for other MBE alloy systems.