All About Hydrogels

Audience: Middle and High School Students

Polyacrylamide hydrogel disks. Photo by Sci News

If you’ve seen news regarding biomedical engineering lately, you might’ve heard about hydrogels! These tools have been creating waves in the scientific world for enhancing things such as drug delivery and wound healing. Hydrogels are crosslinked polymer chains with three-dimensional (3D) network structures, which can absorb relatively large amounts of fluid

Think of Jell-O and related sweet, wiggly snack treats as the forefathers of modern hydrogels. Those edible gelatins are also mostly water (about 90 percent in Jell-O’s case). But the water doesn’t leak out. Because of their high water content, soft structure, and porosity of hydrogels, they closely resemble living tissues.

Hydrogels comprise a three-dimensional (3D) network that can absorb a large amount of water. They can be flexible and soft, which results from their water absorption ability. The sources of hydrogels can be divided into natural, synthetic, or semi-synthetic polymers. Regardless of their source, they have inherent biocompatibility, bioactivity, and biodegradability, meaning that they are friendly to living systems, interact with our body, and disappear when the job is done. These qualities make them sought-after in medical fields. However, hydrogels have relatively weak stability and mechanical strength, meaning that they can be easily damaged or broken when pushed, pulled, or squished. Also, certain individuals may have an allergic reaction to the hydrogels. 

Over the past 60 years, hydrogels have been engineered to be implantable, injectable, and sprayable for many organs and tissues. Because of this, hydrogels have received considerable attention in the past 50 years, due to their exceptional promise in a wide range of applications, which include: 

• Lab-grown tissues (tissue engineering): Scientists can grow skin cells in petri dishes, but these cells develop into flat sheets. Lab-grown cells won’t form the organized layers found in our skin. So today, many biologists supply human tissues grown in the lab with hydrogel frameworks.

• Contact lenses (oxygen diffusers): The tear-moistened surface of your eye’s cornea allows oxygen to diffuse directly from the air into your eyeball, but when you wear contact lenses, they cover the eyes and cut off exposure to oxygen. To avoid that, soft lenses now depend on hydrogels. Their water-swollen polymers allow oxygen to reach the eye pretty much as normal.

• Water absorbers: There are hydrogels that can absorb 3,000 times their weight in water! This makes them beneficial in a number of fields. For example, diapers and sweat-absorbent clothes. Also in agriculture, to diffuse water into the soil.

• Drug-delivery systems: Some medicines come packed in hydrogels. They travel into the body’s targeted area and assist the healing of deep wounds by slowly releasing their contents into the moist tissues around the wound.

In conclusion, hydrogels are pretty cool, and their variety of uses makes them able to advance many fields, from agriculture to engineering to medicine. As we get better at engineering these "smart" materials, medicine will become less invasive. For example, their biodegradability will allow for fewer surgeries. In the future, hydrogels may allow us to 3D-print entire replacement organs or "self-healing" bandages that know exactly when a wound is healed. So the next time you eat or see some Jell-O, remember that you might be looking at the future of human health!

Bibliography

Enas M. Ahmed, “Hydrogel: Preparation, characterization, and applications: A review”, Journal of Advanced Research, vol 6.2, 105-121, https://doi.org/10.1016/j.jare.2013.07.006. (https://www.sciencedirect.com/science/article/pii/S2090123213000969). Accessed 26 March 2026.

Carpenter, Katie Grace. “Explainer: What is a hydrogel?” Science News Explores, 21 November 2022, https://www.snexplores.org/article/explainer-what-is-a-hydrogel. Accessed 26 March 2026.

Ho, Tzu-Chuan et al. “Hydrogels: Properties and Applications in Biomedicine.” Molecules (Basel, Switzerland) vol. 27,9 2902. 2 May. 2022, doi:10.3390/molecules27092902. Accessed 26 March 2026.