What are hydrogels?

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Posted on September 8, 2025

What are hydrogels?

Hydrogels are materials that can absorb and hold large amounts of water. They are made up of hydrophilic functional groups that attach to polymers and are cross-linked via hydrogen bonding and other interactions to form a three-dimensional mesh structure. A hydrogel’s capacity for water absorption largely depends on the strength of cross-linked bonds, the hydrophilicity of functional groups, the outside environment, and its swelling ratio [1].

There are both natural- and synthetic-polymer hydrogels. Natural-hydrogel polymers include polysaccharides, polynucleotides, and polypeptides. These polymers are particularly beneficial because they are abundant in nature, biodegradable, and inexpensive. Some examples of natural hydrogels include collagen, silk fibroin, and hyaluronic acid. Synthetic-polymer hydrogels differ from natural polymers because they have chemical and physical properties that can be altered more easily in synthesis to meet specific demands [1, 2].

Relevant Applications to the U.S. Department of Defense (DoD)

Biological Decontamination

Hydrogels can be modified to decontaminate surfaces that have come in contact with biological agents. A hydrogel-based biosynthetic polymer developed by the U.S. Army Edgewood Chemical Biological Center and CBI Polymers can be applied to a surface and, once dry, be peeled away to remove harmful bacteria and chemicals [3].

Severe Tissue Trauma in War

Hydrogels can be used to save military lives because of their unique properties that allow them to be most effective in preventing hemorrhaging from injury in war. Because of their aqueous nature, hydrogels very closely mimic human soft tissue and are therefore very useful in scaffolds supporting regeneration of damaged tissue and cell growth. Hydrogels are also very useful in wound dressings, where they promote healing and prevent infection [4].

Common Electronic Applications

The gel-like structure of hydrogel electrolytes is created from cross-linking a mixed solution of electrolytes and aqueous polymer. The resulting structure holds electroconductive properties that can be used in the following applications [5]:

  • Electrochemical capacitors operating in aqueous environments

  • Zinc anodes in aqueous zinc-ion batteries

  • Flexible energy-storage devices (supercapacitors rechargeable batteries)

  • Wearable sensors and energy storage

Additional Resources

Latest Related News/Articles

References

[1] Fundamental Concepts of Hydrogels: Synthesis, Properties, and Their Applications (PubMed Central)

[2] Overview of Natural Hydrogels for Regenerative Medicine Applications (Springer Nature)

[3] Army Researchers Explore Use of Gels for Biological Decontamination (U.S. Army)

[4] Applications of Hydrogels in Emergency Therapy (PubMed Central)

[5] Hydrogel Polymer Electrolytes: Synthesis, Physicochemical Characterization and Application in Electrochemical Capacitors (PubMed Central)