Harvard University researchers have recently manipulated the underlying structure of a single material to make a hydrogel characterized as both tough and stretchy.

As specified in a Science report, this water-absorbing material akin to soft tissues has been employed in countless biomedical applications, from contact lenses to coatings in pills.

Nonetheless, it is a struggle to create hydrogels that can hold up persistent stresses; after adequate use, many reach a "breaking" point, a site where they are stretching out and cannot go back to their original shape.

Essentially, hydrogels are made of polymer strands sticking together in a couple of ways. First, the chemical bonds are called "cross-links," and the second, entanglements, in which a single polymer chain weaves around another. Increasing the number of cross-links develops a more inflexible, breakable hydrogel.

The researchers discovered that when they increased the number of entanglements along every chain, from just a single or two to over 100, they made the material that was strong, yet remained stretched enough to employ as an artificial muscle, or for the surface of an artificial joint to be coated. The thick entanglements enabled the chains to slip around and pull on one another, minus breaking.

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Science Times - Long-Lasting Hydrogel Could Help Replace Breakage in Human Tissues; Link of This Water-Absorbing Material to the Approach Explained
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The gel stiffness increases after crosslinking and can be easily picked up with a pair of forceps while remaining optically transparent.

Chemical Crosslinking 

Hydrogen molded by chemical crosslinking exhibits greater stability, longer sturdiness, and higher mechanical properties, including shear, bending, and tensile, among others, compared with physically crosslinked hydrogels.

Essentially, chemical crosslinked hydrogens are produced by grafting functional monomers into the polymer linkage or employing a crosslinker to pair a couple of polymer chains.

In addition, chemical crosslinking reaction mechanisms depend on the functional groups' crosslinking of the polymers with crosslinkers like aldehydes and N, N-N-ethyl carbodiimide.

Radical reactions can be stimulated as well by applying high-energy irradiation like the UV, electron beam, gamma, and microwave, and water-soluble polymers can be "derivatized" with the employment of vinyl groups that exist in their structures or radicals developed through the breaking of chemical bonds.

Hydrogels for the Preparations for Biomaterials

As mentioned earlier, hydrogels are water-absorbing, three-dimensional linkages of polymer chains with the ability to hold great amounts of water.

ScienceDirect report said these are the initial biomaterials developed for application in the human body and are discovering extensive biomedical applications. New approaches to the synthesis of hydrogels have transformed the field of biomaterials.

Various studies have presented various aspects of the synthesis of hydrogels, including their benefits and limitations and the various synthetic hydrogels like composite, biodegradable, superabsorbent, and stimuli-sensitive hydrogels.

Moreover, natural and biocompatible hydrogels like the alginate-, protein- and chitosan-based hydrogels are also being discussed in certain research.

Earlier Related Report

In 2020, a report by Journal Material Chemistry A said hydrogen's emerging applications in flexible electronics necessitate hydrogels to possess exceptional anti-fatigue breakage, not to mention self-healing properties; this stays an essential undealt scientific challenge.

In this, inspired by human tissues, a simple yet effective approach is suggested to prepare a multifunctional hydrogel that exhibits excessively stretchable, anti-fatigue-breakage, and self-healing properties.

Lastly, the hydrogel exhibits extreme sensitivity in a wide strain window when employed as a strain sensor.

More essentially, benefiting from the self-healable and anti-fatigue-breakage properties, the hydrogel's detecting properties are completely restored following a cutting-and-healing process. More so, it keeps working for quite some time already, even after being seriously impaired.

Related information about hydrogel and tissue regeneration is shown on Chemical & Engineering News's YouTube video below:


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