Materials Science

Let’s learn about hydrogels

These polymer-based materials have an astonishing array of uses

Hydrogels are polymer-based materials sop up water like sponges — and can later release it for a variety of uses.

imageBROKER/Joanna Wnuk/Getty Images

By Maria Temming

What do Jell-O, contact lenses and 3-D printed body parts have in common?

They all rely on hydrogels.

Hydrogels are polymer-based materials that can absorb and release lots of water. These materials are composed of threadlike molecules tangled in a complex mesh. That netting easily snags water, or H2O, molecules. 

Some hydrogels are made of natural polymers. Jell-O is a good example. It contains a natural polymer called gelatin. Other hydrogels are made with synthetic polymers — and can be put to work in many different ways.  

Some hydrogels can suck moisture out of the air and release it for drinking water. Others can collect H2O from dirty water while leaving pollutants behind. Hydrogels can even be added to soil. When someone waters their crops, those hydrogels soak up the moisture and release it slowly. That keeps water from flowing or evaporating off the soil.

Hydrogels are especially useful for making stuff that must touch living tissue. That’s because hydrogels and living tissue are both mostly water. Hydrogels have been used to make contact lenses and medical implants. Some engineers have also used hydrogels to 3-D print human tissues for transplants. The bioinks used to print these tissues mix live cells with a hydrogel ooze that protects the cells.

Want to know more? We’ve got some stories to get you started:

A new hydrogel could help pull drinking water from the air The salty gel absorbs more water from the air than similar gels, even in desert climates. This could provide clean water for drinking or farming. (11/3/2023) Readability: 6.8

A new solar-powered gel purifies water in a flash The unusual, fruit-inspired structure of this material provides quick filtration that could satisfy people’s daily water needs. (4/8/2023) Readability: 6.9

New patch might replace some finger-prick testing of blood sugar One teen’s hydrogel-based device tests glucose in sweat to signal when insulin is needed. (5.18/2023) Readability: 8.0

What’s a hydrogel and what’s it good for? MIT explains.

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Activities

Word find

If you’ve got a green thumb, try this experiment from Science Buddies and test how well hydrogels help conserve water in farming. Prefer to take a spa day? Science Buddies has another hydrogel experiment for you — testing the moisturizing power of hydrogel face masks.

Power Words

More About Power Words

3-D: Short for three-dimensional. This term is an adjective for something that has features that can be described in three dimensions — height, width and length. 

bioink: A liquid for use with a 3-D printer that carries cells to be deposited, drop by drop, into specific places for the creation of living tissue.

cell: (in biology) The smallest structural and functional unit of an organism. Typically too small to see with the unaided eye, it consists of a watery fluid surrounded by a membrane or wall. Depending on their size, animals are made of anywhere from thousands to trillions of cells. Most organisms, such as yeasts, molds, bacteria and some algae, are composed of only one cell.

collagen: A fibrous protein found in bones, cartilage, tendons and other connective tissues.

crop: (in agriculture) A type of plant grown intentionally grown and nurtured by farmers, such as corn, coffee or tomatoes. Or the term could apply to the part of the plant harvested and sold by farmers.

engineer: A person who uses science and math to solve problems. As a verb, to engineer means to design a device, material or process that will solve some problem or unmet need.

hydrogel: A “smart” polymer-based material that can change its structure in response to its environment, such as the local temperature, pH, salt or water concentration. The polymers that make up a hydrogel have water-attracting ends sticking out. Those ends help hydrogels latch onto molecules of water. Some hydrogels are used in baby diapers to hold urine. Others are added to potting soils to hold water near to plants until they need it. Still others may be part of wound dressings to prevent a sore from drying out.

implant: A device manufactured to replace a missing biological structure, to support a damaged biological structure, or to enhance an existing biological structure. Examples include artificial hips, knees and teeth; pacemakers; and the insulin pumps used to treat diabetes. Or some device installed surgically into an animal’s body to collect information on the individual (such as its temperature, blood pressure or activity cycle).

moisture: Small amounts of water present in the air, as vapor. It can also be present as a liquid, such as water droplets condensed on the inside of a window, or dampness present in clothing or soil.

molecule: A group of atoms that represents the smallest possible amount of a chemical compound. Molecules can be made of single types of atoms or of different types. For example, the oxygen in air is made of two bound oxygen atoms (O2). Water is made of two hydrogen atoms and one oxygen atom (H2O).

pollutant: A substance that taints something — such as the air, water, our bodies or products. Some pollutants are chemicals, such as pesticides. Others may be radiation, including excess heat or light. Even weeds and other invasive species can be considered a type of biological pollution.

polymer: A substance made from long chains of repeating groups of atoms. Manufactured polymers include nylon, polyvinyl chloride (better known as PVC) and many types of plastics. Natural polymers include rubber, silk and cellulose (found in plants and used to make paper, for example).

synthetic: An adjective that describes something that did not arise naturally, but was instead created by people. Many synthetic materials have been developed to stand in for natural materials, such as synthetic rubber, synthetic diamond or a synthetic hormone. Some may even have a chemical makeup and structure identical to the original.

tissue: Made of cells, it is any of the distinct types of materials that make up animals, plants or fungi. Cells within a tissue work as a unit to perform a particular function in living organisms. Different organs of the human body, for instance, often are made from many different types of tissues.

transplant: (in medicine) The replacement of organs, tissues or cells with those from another organism. It is also a term for the material that will be moved.

About Maria Temming

Maria Temming is the Assistant Managing Editor at Science News Explores. She has bachelor's degrees in physics and English, and a master's in science writing.

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