What do a flea and an eagle have in common? They can store energy in their feet without having to continuously contract their muscles to then jump high or hold on to prey. Now scientists at Queen Mary University of London and University of Cambridge have created materials that can store energy this way, be squeezed repeatedly without damage, and even change shape if necessary.
These kinds of materials are called auxetics and behave quite differently from regular materials. Instead of bulging out when squeezed, they collapse in all directions, storing the energy inside.
Current auxetic material designs have sharp corners which enable them to fold onto themselves, achieving higher density. This is a property that has been recognised recently in lightweight armour designs, where the material can collapse in front of a bullet upon impact. This is important because mass in front of a bullet is the biggest factor in armour effectiveness.
The sharp corners also concentrate forces and cause the material to fracture if squeezed multiple times, which is not a problem for armour as it is only designed to be used once.
In this study, published in Frontiers in Materials, the team of scientists redesigned the materials with smooth curves which distribute the forces and make repeated deformations possible for other applications where energy storing and shape-changing material properties are required.
The work lays the basis for designs of lightweight 3D supports, which also fold in specific ways and store energy which could be released on demand.
Principle investigator Dr Stoyan Smoukov, from Queen Mary University of London, said: “The exciting future of new materials designs is that they can start replacing devices and robots. All the smart functionality is embedded in the material, for example the repeated ability to latch onto objects the way eagles latch onto prey, and keep a vice-like grip without spending any more force or effort.”
The team expects its nature-inspired designs could be used in energy-efficient gripping tools required in industry, re-configurable shape-on-demand materials, and even lattices with unique thermal expansion behaviour.
Eesha Khare, a visiting undergraduate student from Harvard University who was instrumental in defining the project, added: “A major problem for materials exposed to harsh conditions, such as high temperature, is their expansion. A material could now be designed so its expansion properties continuously vary to match a gradient of temperature farther and closer to a heat source. This way, it will be able to adjust itself naturally to repeated and severe changes.”
The flexible auxetic material designs, which were not possible before, were adapted specifically to be easily 3D-printed, a feature the authors consider essential.
Dr Smoukov added: “By growing things layer-by-layer from the bottom up, the possible material structures are mostly limited by imagination, and we can easily take advantage of inspirations we get from nature.”
The Latest on: Auxetic materials
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The Latest on: Auxetic materials
- 3D-printed flexible mesh supports customization of prosthetic and implantable medical deviceson October 1, 2020 at 5:00 pm
3D-printing innovation adjusts material's stickiness The team also developed two other ... Finally, the team designed meshes that incorporated auxetic structures, patterns that become wider when you ...
- New material thickens as it’s stretchedon September 29, 2020 at 5:00 pm
Materials in nature exhibit this type of auxetic behavior—think cat skin and tendons in the human body—but until now it has only been replicated synthetically by structuring conventional materials ...
- Three-dimensional printing of functionally graded liquid crystal elastomeron September 26, 2020 at 1:24 am
1 Materials Science and Engineering Program ... To measure the Poisson’s ratios of printed auxetic lattice structures, we first mark four points on a printed lattice. The four points can be regarded ...
- Dainese Release Revamped Trail Skins Protection Lineon September 24, 2020 at 11:22 am
The construction of the Pro-Shape 2.0 protectors is inspired by the geometry of auxetic materials present in nature that, following an impact or stress, expand in all directions simultaneously ...
- Advanced Compositeson September 22, 2020 at 10:13 pm
Composite materials are replacing traditional ones at an unprecedented rate due to the global demand for lightweight structures (eg in aircraft, wind turbines, construction and automotive industries).
- 3D printed smart swab could alleviate COVID-19 test concernson September 9, 2020 at 7:31 pm
Arjunan said 3D printing is the most versatile technique for developing auxetic meta-materials, but limitations are presented due to the requirement of the support structure. “While these supports can ...
- This New Material Thickens as it Stretcheson September 8, 2020 at 5:00 pm
In a study published in Nature Communications the researchers note these so-called “auxetic materials” can be found in nature in the skin of cats, in human tendons, and in the protective layer inside ...
- Wolverhampton uni team design 3D-printed swab that could test for viruson September 8, 2020 at 2:52 am
“In this regard, our research expertise in additive manufacturing and meta-materials led to the development of auxetic nasopharyngeal swabs that can shrink under axial resistance. “This allows ...
- GCSE Design and Technology: Auxetic materials used in protective wearon October 21, 2019 at 5:06 pm
An explanation of the auxetic material found in the inner layer of a mussel shell and how it absorbs impact by becoming denser when stretched. At Sheffield Hallam University, engineers are ...
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