Materials

Fiber-reinforced hydrogel is 5 times stronger than steel

The newly developed fiber-reinforced hydrogel consists of polyampholyte gels and glass fiber fabric
The newly developed fiber-reinforced hydrogel consists of polyampholyte gels and glass fiber fabric
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The newly developed fiber-reinforced hydrogel consists of polyampholyte gels and glass fiber fabric
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The newly developed fiber-reinforced hydrogel consists of polyampholyte gels and glass fiber fabric
Scanning Electron Microscopy (SEM) images of the fiber-reinforced hydrogels
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Scanning Electron Microscopy (SEM) images of the fiber-reinforced hydrogels

Hydrogels have shown significant potential in everything from wound dressings to soft robots, but their applications have been limited from their lack of toughness – until now. A team of scientists at Hokkaido University have developed a new set of hydrogel composites or "fiber-reinforced soft composites" that combine hydrogels with woven fiber fabric to create a material that is five times stronger than carbon steel.

Composite materials have been around for millennia and the principle is very simple. A very soft substance like mud can be made strong enough to make bricks by adding straw as a tempering material. The same applies to adding crushed pottery to brick, seashells fragments to ceramic, or glass fiber to plastic.

The latter is very similar to the fiber-reinforced hydrogel. Hydrogels are made of hydrophilic polymer chains that absorb up to 90 percent water. They aren't very strong or durable, but by adding glass tiny fibers the researchers created a tough, bendable, stretchable material.

Scanning Electron Microscopy (SEM) images of the fiber-reinforced hydrogels
Scanning Electron Microscopy (SEM) images of the fiber-reinforced hydrogels

According to the team, the composite hydrogel is remarkably strong, probably due to dynamic ionic bonds between the fiber and hydrogels, and within the hydrogels. In tests using polyampholyte gels and a single glass fiber measuring 10μm in diameter, the material turned out to be 25 times tougher than glass fiber fabric, 100 times tougher than hydrogels, and five times as strong as carbon steel, based on the amount of energy needed to destroy them.

"The fiber-reinforced hydrogels, with a 40 percent water level, are environmentally friendly," says Dr Jian Ping Gong, "The material has multiple potential applications because of its reliability, durability and flexibility. For example, in addition to fashion and manufacturing uses, it could be used as artificial ligaments and tendons, which are subject to strong load-bearing tensions."

The research was published in Advanced Functional Materials.

Source: Hokkaido University

11 comments
plum cheri
The information I would like to see on ALL new materials is whether or not it is biodegradable and if not, why not.
Bob Stuart
"Five times as strong as carbon steel, based on the energy needed to destroy them" translates into "5X tougher." "Strength" usually refers to tensile strength, or sometimes to specific tensile strength. As for the straw reinforcing making mud a useful material, while fibers of any scale work in concrete, the Israelites and the Egyptians got in a tiff over straw at the brickworks because it kept the bricks from cracking due to drying on the outside first. After baking and shrinkage of the matrix it would only come into play to hold a crack loosely together.
jaison Sibley
I wish airline industry uses this as outer coating for planes . It will reduce the incidence of damage plus the water content will reduce the cosmic radiation all travellers get exposed to at high altitude ( detrimental to frequent flyers like pilots/steweardess....with much higher cancer rates than general population ) . I am not sure about the weight per square inch but I am sure they can manage to make close weight per square inch as the current composites .
Ralf Biernacki
@cheri: It's intended as a structural material. I sure hope it is not biodegradable, for obvious reasons. <p> As for bricks, the straw gets pyrolyzed when the bricks are fired, so it is not serving as a reinforcement in the end product. <p> What I find interesting in this material is that the hydrogel actually makes the glass fibers stronger. I guess the mechanism has to do with somehow inhibiting surface cracks---the article says something vague about "dynamic ionic bonds". Anyone has a more detailed explanation?
piperTom
This stuff is "five times stronger than carbon steel." Just so we are all on the same page, "carbon steel" is a unspecific reference to various lower quality steels. It still might be helpful to know: five times stronger than HOW MUCH steel? same weight? same volume? Given all this, all we really read here is "it's strong".
notarichman
as usual, the reporter did not get specific data on "strength". there are lots of ways to measure strength. tensile is one way only. however, let's say that it is useful and the idea behind the invention is even more useful...then why not try melted basalt rock fibers? it is supposed to be 7 times stronger than steel for tensile strength?
Douglas Bennett Rogers
It looks like the effective fiber strength is increased. The effective fiber strength is represented by the Weibull-Turner curve, which is an S curve. The vertical part of the S is at 68% glass content in an epoxy matrix. The lower part of the S is around 300 k psi and the upper at around 600 k psi. The internal strength of glass is about 3 M psi. The fiber strength between surface flaws approaches this. The surface area of the cylinder defined by two flaws times the shear strength of the bond determines the tensile strength of the composite. Since this is a weak matrix, it must be rounding out the flaws. Silica is slightly soluable in water.
beergas
Seeing "researchers created a tough, bendable, stretchable material" and the initial use would be in areas of fashion & manufacturing the first versions would seem solid enough for general use. Clothing ends up in land fill or third world gifts anyway so no need for aircraft standards at this point. High water content suggests it will break down nicely. All in all looks worthy of more research. Be watching if any US stocks pick up on the techniques now that infrastructure & defense on the table from present admin. Can see lots of use for this and low cost inputs would help speed the process.
Grunchy
Even more important than biodegradability is how non-biodegradable it is. That is to say, how inert it is in the environment. (Most of these synthetics break down when exposed to UV and ozone, which is ok if you don't mind replacing it all the time; or else it has to be protected with paint.)
jhhenao
Si ese material es 5 veces más fuerte que el acero, como es que el que lo tiene en la mano lo dobla tan fácilmente como se nota en la imagen?
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