It is a fact that our modern life is closely linked to the use of plastics, but as we know, most plastics are synthetic products derived from fossil sources, and have caused a strong environmental problem associated with their accumulation and persistence in the environment, greatly altering ecosystems, especially marine ecosystems. Although bioplastics have offered a sustainable and more environmentally friendly alternative, the reality is that their implementation has not been achieved to a great extent due to their limited mechanical properties and complex production processes. Therefore, if we want to advance in the substitution of plastics of petrochemical origin, the alternative is to develop resistant and sustainable materials.
A new method to replace plastics. Source: image designed by @emiliomoron, contains public domain image.
This could change with new research, a team of researchers from the University of Science and Technology of China (USTC) recently reported a method for making materials with a structure similar to mother-of-pearl, using wood-derived fibers and mica, with good characteristics for mass production and easy to color. The results were presented in the magazine Nature Communications.
Using the biomimetic design, as a strategy to improve the characteristics of the materials, this group of scientists were inspired by the nacre, which presents a structure that combines strength and resistance in a totally natural material, to imitate its ordered structure of bricks and mortar using a mica micro plate coated with TiO2 (TiO2-mica) and cellulose nanofiber (CNF), through a new method developed.
Inspired by the brick and mortar microstructure of nacre, a hierarchically ordered structure design at multiple scale levels was employed, using cellulose nanofibers as one of the most abundant all-green resources on Earth, which can be obtained from plants or produced by bacteria. In addition, it has high strength, a low coefficient of thermal expansion and abundant hydroxyl and carboxyl groups on the surface, making it ideal as a biopolymer for this structure. Also used is the all-natural mica microplate, which is commercially available and has been widely used in pigments or cosmetics due to its beautiful pearl color. And nanograms of TiO2 are used as the only inorganic material, but which is suitable for making sustainable structural materials from nacre.
Schematic illustration of directional deforming assembly method. Source: Image adapted by @emiliomoron with research data.
For its production, a mica hydrogel of TiO2 and CNF is directly pressed, while maintaining the size in the directions of the plane without change. The thickness of the hydrogel is considerably reduced and the materials directly acquire a highly ordered brick and mortar structure. Using this method of directional deformation assembly, it was possible to manufacture totally natural, high performance bio-inspired structural materials with better mechanical and thermal properties than petroleum-based plastics. The good processability and the tunable coloration are characteristics obtained in this type of material and that give it the possibility of becoming an alternative for the manufacture of beautiful and durable structural materials to replace plastics in applications such as the structural support of personal electronic devices.
In conclusion, from the perspective of replacing the rigid plastic used to provide structure in electronic devices, this new method, which imitates the highly ordered structure of nacre, can contribute to overcoming the limitation of the poor mechanical properties of bio-based materials, which have limited their use in a greater number of applications. And if complex manufacturing processes can also be simplified, all-natural, bio-inspired structural materials could be good competitors to petroleum-based plastics, giving us a viable alternative for their replacement.
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