Recently, the team of Academician Yu Shuhong of the University of Science and Technology of China used the bionic structural design concept to develop a new material manufacturing method called "directed deformation assembly". The team used the above method to coat mica sheets coated with cellulose nanofibers and titanium dioxide. Compound, prepare high-performance sustainable structural materials with bionic structures, which have better mechanical and thermal properties than petroleum-based plastics, and are expected to become plastic substitutes.




 

Picture | Academician Yu Shuhong




A few days ago, the paper was published on Nature Communications under the title (An all-natural bioinspired structural material for plastic replacement).




The first research paper, Dr. Qingfang Guan, told DeepTech that this new material adopts the structural design of imitated mother-of-pearl. The bionic design can effectively improve the mechanical properties of the material, and can prepare high-performance materials based on ordinary natural substances. Excellent characteristics of high strength and high toughness.




 

Figure | Schematic diagram of directional deformation assembly method

 




Multi-scale bionic structure design and surface chemical control







In the research, the team used multi-scale bionic structural design and surface chemical control to construct this natural bio-based sustainable structural material with high strength and toughness.




Specifically, the use of titanium dioxide-coated mica flakes as the bricks in the bionic structure, on the one hand, provides structural materials with much higher strength than engineering plastics. On the other hand, through the use of crack deflection and other bionic structural principles, the toughness and crack growth resistance of the material have been greatly improved, thus laying a solid foundation for the material as an emerging sustainable material to replace the existing non-degradable plastics. .




 

Figure | Preparation and characterization of new biomimetic nano-cellulose materials




Experiments show that the bionic structural material not only has much higher strength than engineering plastics, but also has strong toughness and crack propagation resistance. In the temperature range of minus 130 degrees Celsius to 150 degrees Celsius above zero, its size will not change, which is in sharp contrast to the sharp shrinkage and expansion of plastic.




At room temperature, its thermal expansion coefficient is only about one-tenth that of most plastics.

  

Modern life is closely dependent on plastics, but the amount of plastics is huge, most of which come from petrochemicals. For these complex environmental problems, although there is no panacea, improving the performance of bio-based materials through bionic structural design can become a promising strategy.




 

Figure | Comparison of mechanical and thermal properties of new bionic nano-cellulose materials and polymers

  

In this regard, Yu Shuhong’s team developed a simple and efficient bionic method called "Directed Deformation Assembly". Using the deformation assembly method, the team produced an all-natural high-performance bionic structural material. At the same time, it also prepared a composite hydrogel of cellulose nanofibers (CNF) and titanium dioxide mica flakes (titanium dioxide-mica).




As one of the most abundant all-green resources on earth, CNF, high-performance one-dimensional (1D) cellulose nanofibers, can be extracted from plants or produced by bacteria. It has high strength (at least 2 GPa), low coefficient of thermal expansion (CTE) (1×10−7 K−1), and a large number of hydroxyl and carboxyl groups, indicating that it is an ideal biomass-based structural unit.

  

Mica flakes come from natural mica, which is a natural two-dimensional (2D) inorganic material. Based on mica flakes, titanium dioxide mica is commercially available, and because of its unique and beautiful pearlescent color, it has been widely used in pigments or cosmetics.




In addition, the surface of the titanium dioxide mica flakes is consistent with the surface of the aragonite flakes, and there are a large number of nanoparticles with a particle size between 10 and 100 nm. Therefore, titanium dioxide mica flakes (titanium dioxide-mica) composite hydrogel is a suitable two-dimensional inorganic building block to make bionic sustainable structural materials.




 

Figure | Mechanical properties of nano-cellulose new bionic materials




The resulting high-performance sustainable bionic structural material has good mechanical and thermal properties. As an emerging structural material, it has better performance than petroleum-based plastics, with adjustable colors, safer and more reliable, and it is expected to become a strong competitor of petroleum-based plastics.




If it can be mass-produced, coupled with excellent processing properties and adjustable coloring, the material will be used to manufacture beautiful and durable structural materials, and it has broad application potential in the structural materials of various electronic devices.




 

Figure | Thermal performance comparison between new bionic nano-cellulose materials and high-performance plastics




"Directed Deformation Assembly" Technology

 




Speaking of this research, Guan Qingfang said that after billions of years of evolution, nature has created countless ingenious structures. For example, the tongs of the mantis shrimp have a layered oriented spiral structure, the shell nacre has a "brick mud structure", and natural wood has an oriented pore structure.




Due to the sophisticated structure on these multi-level scales, it has excellent performance. Therefore, in terms of material design and manufacturing strategy, the team was inspired by the multi-scale structure of the nacre, and used the multilayer layered performance based on pure natural materials to carry out an orderly structural design.




The main challenge encountered in this research is to process natural component structural units into high-performance structural materials. In the process, they tried many methods in order to explore new methods that can produce high-performance bionic materials on a large scale. In the end, the team explored the "directed deformation assembly" method, realized a sophisticated structural design, and realized the manufacture of high-performance sustainable bionic structural materials.




Talking about the research principle of "directional deformation assembly" bionic new materials, the researchers told DeepTech that "directional deformation assembly" specifically refers to keeping the dimensions in the other two directions unchanged under the action of pressure and reducing the thickness of the material. , So as to realize the orderly orientation arrangement of the two-dimensional sheet layer, and finally form a highly ordered "brick mud structure", and then obtain high-performance sustainable bionic structural materials.




In addition, "directional deformation assembly" can be expanded in that in a restricted system, the dimensions in other directions are kept unchanged, and the dimensions in one direction are changed in orientation to achieve the expected orderly structure design.






Figure | The microstructure of the new bionic nano-cellulose material




In the specific implementation process, the "directed deformation assembly" overcomes the limitations of traditional bionic materials preparation conditions and processing methods. The research team achieved a sophisticated bionic structural design through simple and scalable methods, which is also the scale of high-performance bionic new materials. An important exploration on the road to chemical production.