On June 3, Nature officially published "Design of robust superhydrophobic surfaces"，the finding of professor Zhou Tianfeng of Beijing Institute of Technology (BIT), professor Deng Xu of University of Electronic Science and Technology of China and professor Robin H. A. Ras of Aalto University in Finland. The research achievement was selected as the cover of current period. The paper proposes the decoupling mechanism to split the surface wettability and mechanical robustness into two different structural scales. By separately designing optimally on the two structural scales, a superhydrophobic surface is created with microstructural "armor", which has excellent mechanical robustness. The "armor" structure solves the key problem of insufficient mechanical robustness of superhydrophobic surfaces.

　　Due to its unique solid-liquid interface properties, the superhydrophobic materials of bionic lotus leaf have shown great application potential in fields such as surface self-cleaning, biological antifouling, waterproof and anti-icing, fluid drag reduction and heat and mass transfering, and then have developed a series of superwetting system theories such as superhydrophilicity and superoleophobicity. The micro/ nano rough structure will produce high local pressures under mechanical load, making it fragile and highly susceptible to abrasion. Additionally, abrasion exposes the underlying materials, changing the local chemical nature of the surface from hydrophobicity to hydrophilicity, resulting in the pinning of water droplets to the surface. It has long been thought that the mechanical robustness and water repellency are two mutually exclusive surface properties, as the so-called "You can't have your cake and eat it". Therefore, how to both ensure good superhydrophobic properties and achieve strong mechanical robustness is the key problem that urgently need to be solved concerning the practical application of superhydrophobic materials.

Design of microstructural armor

Armored superhydrophobic surface exhibits excellent mechanical robustness.

Based on a brand-new idea, for the first time, this paper splits superhydrophobicity and mechanical robustness into two different structural scales through the decoupling mechanism, and proposes the concept of microstructure "armor" to protect superhydrophobic nanomaterials from friction and abrasion. The glass armored surface not only integrates high-strength mechanical robustness, resist chemical corrosion and thermal degradation as well as high-speed jet impact and condensation failure, but also achieves high light transmittance of the glass armored surface, which create necessary conditions for the surface application in self-cleaning vehicle glass, solar cell cover panel, and architectural glass curtain walls. BIT takes advantage of its manufacturing of glass micro-nano structures and uses glass molding to realize the manufacture of glass armor for inverted pyramid array microstructures. The innovative design ideas and general manufacturing strategies of this paper show the extraordinary application potential of armored superhydrophobic surfaces, which will further promote superhydrophobic surfaces into a wide range of practical applications.

Link to the full paper: https://doi.org/10.1038/s41586-020-2331-8

Manufacture of glass armor with inverted pyramid array microstructure

In addition, Zhou Tianfeng's team has made new progress in the field of two-level micro-nano structure manufacturing. The international top journal in materials,Materials and Design, publishes the original research results of professor Zhou Tianfeng of BIT in the field of two-level iridescent structural design and manufacture "Generation of high-saturation two-level iridescent structures by vibration-assisted fly cutting".

Design and manufacture of micro-nano two-level iridescent structure

In this research, the team of Zhou Tianfeng designs and manufactures the micro-nano two-level structure of the diffraction grating composed of micro grooves, and establishes the mapping relationship between the shape and the diffraction color of the two-level structure, and directly induces the iridescent pattern through coding. The team first proposes vibration-assisted fly cutting (VAFC), developes the VAFC test platform and achieves efficient ultra-precision manufacturing of two-level iridescent structures with high-saturation and uniformity through optimized machining parameters by the numerical simulation. The micro-nano two-level structure is expected to be applied in multi-color printing, micro-display/ projector, trademark anti-counterfeiting and invisibility.
Link to the full paper: https://doi.org/10.1016/j.matdes.2020.108839

Introduction attached to the author:
Zhou Tianfeng, male, the Han nationality, member of Communist Party of China, doctor of engineering, professor of School of Mechanical Engineering, BIT, PI of Institute of Engineering Medicine, BIT, doctoral tutor, "Young 973 Project Chief Scientist", was selected to the "High-level Talent Program" and "Huo Yingdong Education Fundation" support plan. Focusing on the research of "micro-nano structural machinery manufacturing", he has achieved innovative results in the preparation of new mold materials, micro-nano mold manufacturing and precision compression molding processes and equipment, and explored the application for micro-nano structures in the fields of optical detection/ guidance, optical fiber communication and medical instruments.

Release Date:2020-06-24

News Source:School of Mechanical Engineering

Translator:Miao Yufei, News Agency of BIT