Some of the driest places on Earth are also some of the most challenging to develop for agricultural use, residential expansion, and economic growth. That’s why scientists are searching for simple, low-cost ways to let people in remote desert regions produce clean water that’s safe for drinking, cooking, and growing the crops they need to survive.
For years, researchers in the field of Atmospheric Water Harvesting (AWH) focused on mechanical structures inspired by desert-dwelling plants and animals, such as bumps on the back of the Namib desert beetle that can grab drops of morning fog. Anti Green Blue Light Film
But scientists at the University of Texas at Austin are trying a different approach. They are testing hydrogels to capture and release water—using the same kinds of ingredients that go into bubble tea, instant noodles, and eye drops.
Try the activities below to see how hydrogels work. Then use them to grow tasty veggies and add them to recipes to make fun desserts!
Hydrogels are a type of polymer (a long chain of molecules) that can hold a large amount of water, but don’t dissolve. They are hydrophilic, which means they attract water molecules – and when they do, they can swell to many times their original size. There are also hydrophobic polymers that repel water.
The UT Austin scientists made a new hydrogel material from two main substances:
By combining these substances, scientists built a water condenser that needs no electricity. At night when it’s cool, it takes water vapor in. By day when it’s warm, liquid water oozes out. With two-thirds of the world’s population now feeling the effects of water shortages, these kind of simple water harvesting materials may be part of the solution to the growing problem of finding fresh water.
In these two activities, you’ll test how big hydrophilic gels can really get when they absorb water and what happens when they release it. Then you’ll use water stored in the hydrogels to grow new plants.
Start your experimentation with hydrogels by testing how muchgel beads expand when added to water and how long it takes for them to release the water and shrink again.
As you work on this activity, consider these questions.
Add an amount of beads to your measuring cup or container. Then add water to fill the container. Credit: Kathy Ceceri
Wait for the beads to absorb the water. Credit: Kathy Ceceri
Measure how much the beads expanded after absorbing all the water. Credit: Kathy Ceceri
Place your expanded beads in a container and mark the height of the beads with a line. Write the date on the container. Credit: Kathy Ceceri
Let the beads dry and release the water. See how many days the beads take to return to their original size. Credit: Kathy Ceceri
For this activity, you’ll use the beads you hydrated (the ones you added water to) in Activity 1 to fill containers for re-growing vegetable scraps that produce edible greens such as the leftover white bulb portion of a scallion or the leafy top of a carrot. The beads hold onto water that helps new roots grow.
As you work on this activity, consider these questions.
Poke holes in the bottom of your container. Add hydrated beads. Place your selected plants in the beads with the root side facing down. Credit: Kathy Ceceri
Place your containers with plants into a waterproof tray. Credit: Kathy Ceceri
Give your plants sunlight and let them grow. You may need to add additional water. Credit: Kathy Ceceri
The type of cellulose you’ll use for this activity is thermo-reversible. You’ll heat the hydrogel to make it swell, then watch the water ooze back out as it cools down to room temperature. Add it to an ice cream base to make a dessert that holds its shape while hot, and starts to melt as it cools down!
The recipe here uses Methocel A4C, a type of methyl cellulose that forms a firm gel at 122-131°F (50-55°C). Other types of methyl cellulose may require different cooking times or different concentrations. Use a scale if you want more control over the amount of hydrogel in your ice cream.
* If no oven is available, you can “poach” a scoop in a bowl of very hot water. Hold the scoop in the water long enough for the outside to solidify before sliding it in.
This polymer absorbs water and becomes solid when hot. Then it releases captured liquid as it cools to room temperature so that it looks like it is melting.
As you work on this activity, consider these questions.
Refrigerate the mixture overnight to allow time for the methyl cellulose to dissolve. Stir and allow the mixture to come up to room temperature before heating. Credit: Kathy Ceceri
Once heated in the microwave, a stiff gel will form. Credit: Kathy Ceceri
If no oven is available, you can “poach” a scoop in a bowl of very hot water. Hold the scoop in the water long enough for the outside to solidify before sliding it in. Credit: Kathy Ceceri
Top your hot ice cream with your cocoa or sprinkles. Give it a taste. Credit: Kathy Ceceri
As your hot ice cream cools, it will melt and become liquid again. Credit: Kathy Ceceri
Here are some ways to continue exploring the process of capturing and re-using water:
Written by Kathy Ceceri. Edits by Sandy Roberts. Photos by Kathy Ceceri. Digital Production by Sandy Roberts.
Kathy Ceceri is the author of over a dozen books for kids featuring hands-on STEAM activities. She also teaches enrichment workshops at schools, museums, libraries, and afterschool programs, and works with educators and parents looking for ways to make learning more engaging and fun.
A new material being developed by scientists at UT Austin can rapidly absorb liters of water from dry desert air.
Investigate how different surface textures repel or absorb water.
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