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The Secret of Abnormal Materials: Why Can Negative Poisson's Ratio Change Material Properties?
In the world of materials science, there is a fascinating class of materials called anomalous materials, which have negative Poisson's ratio. This means that when the material is stretched in one direction, it will also be stretched in the vertical direction at the same time, which is the complete opposite of traditional materials. In traditional materials, stretching usually results in vertical shrinkage.
Abnormal materials are not just an academic concept. In daily life, the application of such materials has penetrated into various fields, from medical devices to sports equipment, everywhere.
History of Abnormal Materials
The word anomaly comes from the ancient Greek word "auxetikos" which means "to promote growth". The term was coined by Professor Ken Evans of the University of Exeter. As early as 1978, Berlin-based researcher K. Pietsch invented the first artificial anomalous material, the RFS structure, also known as the diamond folded structure. Although he did not use the term "auxetic" at the time, he was the first to describe the basic lever mechanism of its nonlinear mechanical response and is therefore considered the founder of anomalous networks.
In 1985, A.G. Kolpakov published the first example of a material with a negative Poisson's ratio, and in 1987, R.S. Lakes from the University of Wisconsin-Madison published the article "Foam Structures with a Negative Poisson's Ratio". further promoted the development of this field. Since then, the study of anomalous materials has gradually attracted widespread attention, especially since 1991, when the number of publications related to this topic increased significantly.
Characteristics of abnormal materials
Abnormal materials often have low densities, which allow their microstructures to move like hinges. This behavior can be explained by a macroscopic implementation of an inelastic string wrapped around an elastic string. When the ends are pulled apart, the inelastic cord straightens, while the elastic cord stretches and coils, increasing the effective volume of the structure. In terms of macro product development, the development of footwear products and bionic prosthetics based on abnormally rotating triangle structures has been widely used.
Interestingly, some biological cells, such as mouse embryonic stem cells, also exhibit abnormal behavior under certain conditions, which gives researchers new imaginations about the potential applications of abnormal materials.
Examples of abnormal materials
Examples of abnormal materials include abnormal polyurethane foam, mouse embryonic stem cell nuclei, alpha-quartz, etc. The special structure of these materials gives them unique properties that make them excellent in a variety of applications. In addition, certain rocks and minerals, graphene, and certain types of polytetrafluoroethylene (such as Gore-Tex) have also been found to have anomalous properties.
With the deepening of research, more and more materials have been found to have abnormal properties. The discussion of these materials and structural behaviors has increased the scientific community's interest and exploration of abnormal materials. However, despite the promise of anomalous materials, widespread practical applications still face many challenges and require more research and development.
Future trends
At present, the research on anomalous materials is becoming more and more popular, and it is gradually transitioning from pure theoretical exploration to practical application experiments. In many fields such as medical care, sports equipment, and building materials, abnormal materials have demonstrated flexibility and excellent performance. Many companies and research institutions have begun to join the exploration of abnormal fields.
Ultimately, these studies may change our understanding of materials and their applications in technology and design.
On this day, we can see that the future of abnormal materials is full of opportunities and challenges. Have you ever thought about how the future material revolution will affect our daily lives?
