Materials of unprecedented strength or state-of-the-art sensors show the versatility of the elastomers "patented" by the spiders.
At the I'mnovation Hub, we always have our eye on the development of new materials, whether for the construction of buildings or new devices. In that sense, nature is a fertile ground to draw inspiration for innovation. Proof of this is the beetle-inspired construction material we talked about recently or the adhesive that mimics the abilities of geckos. This time, the mastery is attributable to spiders, whose webs are one of nature's elastomers.
You've probably heard of the proverbial strength of spider webs. It is a flexible yet incredibly tough material. Without further ado, we will explain the reason for these qualities and what its newest applications are.
In this article, you will find out:
First of all, let's clear up some doubts about this type of material. The term elastomer is derived from "elastic" and "polymer." There you already have a couple of clues about their nature: they are elastic polymers. Thus, these structures are characterized by their stretching potential and ability to regain their natural shape. A basic example of an elastomer of plant origin would be rubber.
Natural elastomers, such as those seen in rubber tend to melt with heat and become brittle with cold. Specific treatments are necessary to make them truly effective. For this reason, since the early 20th century, synthetic elastomers have been displacing natural elastomers. There are more than twenty different types of elastomers, including latex, polyurethane, silicone, and neoprene. Today their applications are practically infinite. Some of the most widespread are
In addition to these everyday applications, elastomers are opening the door to much more revolutionary applications. Let's take a look at some of them.
As we have noted, humans are far from being the first to produce and use elastomers. One of the strongest elastomers in nature incorporates molecules with eight hydrogen bonds and is used by spiders to weave their traps. You have probably read that spider webs are stronger than steel.
The Norwegian University of Science and Technology (NTNU) has looked at this type of molecular structure to develop an ultra-strong material.
Spider webs, especially concentric rings, combine two qualities that do not usually go hand in hand: stiffness and toughness. Until now, in the case of commercial products, the higher the stiffness, the lower the toughness. This is because the higher the stiffness, the lower the energy dissipation. An example is glass, which is stiff but not hard.
Fortunately, researchers at the Norwegian university have combined both characteristics in a new material, which has a hard and softer part. The hydrogen-bonded structure is optimal for dissipating energy, while the soft part is made of a silicon-based polymer known as PDMS.
The material, which in addition to being ultra-strong, could also be self-repairing, has various applications. For example, it could be used in smart clothing thanks to its ability to resist torsion.
Just as elastomers are extremely common in our daily lives, there is an equally ubiquitous material in the field of advanced research. We are talking, of course, about the ubiquitous graphene. One of the latest applications of this carbon-based material takes advantage of the silk structures of spider webs and the flexibility of PDMS, the polymer we saw in the previous case.
As reported in the scientific journal ACS Applied Materials & Interfaces, a Hong Kong University of Science and Technology team has created a new type of highly flexible and sensitive sensor with an E-GWF structure. This stands for "elastomer-filled graphene fabric" and is the key to technology with great potential.
The innovative fabric, which consists of PDMS yarns with a graphene coating, is piezo-resistant. This means that, in addition to being flexible, it is sensitive to variations in the electric field, so it can be used in epidermal sensors and other devices in contact with human skin.
The creation of a material that behaves like human muscles, i.e., that contracts with high responsiveness to stimuli, has been the subject of much research. Fortunately, it seems that elastomers have once again come to the rescue of scientists to take an essential step in this direction.
This time it is liquid crystal elastomers, known as LCEs for short. Researchers at the University of California have applied an electrospinning process to manufacture these synthetic fibers that mimic human muscle.
By using electrospinning, which applies an electrical discharge to the polymer to generate an extremely thin filament, the team has succeeded in creating a material with high tensile strength and high responsiveness to heat or near-infrared light.
This new example of an elastomer could have exciting applications in human muscle reconstructive surgery or the development of robotic muscle systems.
In case anyone hadn't noticed, Superman's cape was purely ornamental. For a material to allow anything remotely resembling flight, it must offer some air resistance, as in the case of a bird's wing. There, if only in terms of realism, the device used by the bat-man was far more functional.
The new material developed at the Caltech labs in the U.S. follows a principle similar to that seen in Batman Begins, where the hero turned his cape into a rigid surface to glide around Arkham.
The fabric developed at this center associated with the University of California is composed of an octahedron-shaped polymer mesh obtained through 3D printing. This fabric, with a structure similar to a chain mail, becomes rigid in the presence of heat.
This is achieved utilizing a layer of liquid crystal elastomers or LCE, the elastomer example we saw in the previous case. When an electric current is applied to them, heat is generated, which shrinks them and causes them to take on a preset shape.
The innovative structure could enable the manufacture of exoskeletons in the field of biomedicine or even temporary shelters in the event of a disaster.
In addition to the examples of elastomers mentioned above, if you want to learn more about materials inspired by plants, birds, and insects, you can take a look at this article on biomimetics.
Sources: Engineering Plastics, Scitech Daily, Nanowerk, Caltech, ACS, https://techxplore.com/news/2021-09-artificial-fiber-spun-liquid-crystal.html
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