6 examples of smart materials

Unlike living beings, capable of reproducing and forming their own matter, materials are considered inert and immutable. However, this is far from always being the case! In recent years, “intelligent” materials have multiplied, capable of modifying their behavior according to their environment, of carrying out an action or of processing and storing information. Here are some pretty incredible examples of the prowess of these smart materials.

A tablecloth that recognizes what is placed on a table

Imagine a tablecloth that suggests a recipe for gratin dauphinois when you place potatoes and cheese on it. Or who warns you if you forget your headphones placed on it. This dream may be close at hand, thanks to a fabric called Capacitive and developed by Microsoft. The latter contains a grid of sensors integrated into the fabric capable of differentiating many objects, such as food, dishes, or even of distinguishing liquids in a glass, such as hot water, cold water, cola or milk. Even more incredible: researchers at the University of Passau have designed a prototype of smart shirt which detects what and how much you eat and drink, with sensors placed in the cervix that scan your neck muscles to observe your swallowing. A way to monitor your diet and level ofhydration, defend the researchers.

A self-repairing screen

Repairing a phone screen is expensive! So if he could fix himself, that would be handy. Several manufacturers are working on shape memory polymers, capable of “Heal” scratches and scuffs shallow after a fall. For example, a team from the University of California has developed a polymer with the addition of an ionic salt, where the chemical bonds form an ion-dipole interaction, a weaker and more dynamic type of bond than seasons covalent. The researchers thus succeeded in stretching the material up to 50 times its usual size, and the latter automatically reattached within a day after being torn. Unlike everyone else polymers tested, it conducts current, allowing it to be used for a phone screen. Another team of Indian Institute of Science Education and Research (IISER) also developed a super hard organic material containing crystals piezoelectric which repairs itself spontaneously when damaged.

A chameleon coating that changes color when stretched

Researchers took inspiration from nature to develop a “Chameleon skin” whose color varies depending on whether it is bent or stretched. Some cash butterflies or beetles thus have imbricated scales one under the other, which reflect the light differently depending on the angle at which it arrives. To reproduce this effect, the team at the University of California at Berkeley in the United States etched rows of ridges onto a film in silicon 1,000 times thinner than a hair. When the pattern, applied to a membrane in silicone, is stretched or bent, the wave length is modified and we perceive a different color. This type of material could thus serve as camouflage, for applications military or like decoration. In 2017, another team from Canadian society Hyperstealth Biotechnology has developed a real “Cloak of invisibility” which bends the light so that only the background remains visible.

A connected dressing that detects and treats infections

Smart textile specialist, the startup Spinali Design presented in January 2019 a bandage that emits a light signal in the presence of bacteria pathogens. This dressing also incorporates a biochemical film that promotes the production by pathogens of antimicrobial agents that will kill it. Other Chinese researchers have also developed a bandage that changes color depending on the pH, the latter becoming more acid during bacterial activity. This type of device is decisive in certain pathologies, as in severe burns or patients diabetics, whose wounds can quickly become infected. Some smart plasters go even further. MIT researchers have thus developed a film in hydrogel flexible and stretchable that delivers medication and turns on according to skin temperature. A biocompatible dressing that could be applied not only to the outer skin, but also to organs inside the body.

A 3D printable hydrogel that changes shape in light

Engineers at Rutgers University in New Jersey took inspiration from the skin of octopuses to create a 3D printable material, capable of changing shape when exposed to light. The octopus and the squid in fact have cells in their skin called chromatophores, which contain pigments that absorb or diffract light. By deforming, these chromatophores modify the distribution of pigments, which allows them to camouflage themselves or to change color. The researchers have designed a hydrogel composed of polydopamine and acrylic acid nanoparticles imitating this structure and 3D printable. They thus created a “Artificial muscle” which contracts or retracts depending on the brightness. This invention could find applications in military camouflage, flexible screens or soft robots.

A material that stores electricity for several months

To store electricity, today we mainly use batteries in lithium, polluting and expensive. However, some materials are capable of naturally storingenergy thanks to their nanoporous structure. Researchers from Lancaster University, in the United Kingdom, have thus developed a MOF (metal-organic framework) or metallo-organic network, loaded with molecules azobenzene. Azobenzene is known to absorb light and change shape as a result. So when the material is exposed to soleil during the summer, it “stretches” a little, like a spring, and thus stores thepotential energy During months. In case of need, in winter for example, energy is suddenly released when the material is heated, like a spring that is released. This material could be applied to homes or offices in addition to conventional heating, or to make self-defrosting windshields.