“To our knowledge, this is the first hydrogel that has been reported to have such tactile and mechanical properties.”Srinivasa Raghavan, University of Maryland
When it comes to kitchen spills, paper towels and rags generally do the job. But using a hydrogel—a gelatin-like material in the form of a dry sheet—researchers have managed to craft a better picker-upper that can absorb and hold about three times more water-based liquid. The method, reported in a paper in Matter, produces an absorbent, foldable and cuttable ‘gel sheet’ that may one day find use in kitchens or operating rooms to soak up liquids.
There are generally two types of materials that absorb liquids – porous materials and hydrogels. Porous materials like cloth and paper are flexible, foldable and easy to use, but not very absorbent. On the other hand, superabsorbent hydrogels made of polymer can soak up more than 100 times their weight in water. However, when dried, these hydrogels become brittle solids that crumble.
“We reimagined what a hydrogel can look like,” says corresponding author Srinivasa Raghavan of the University of Maryland. “What we’ve done is combine the desired properties of a paper towel and a hydrogel.”
To craft the gel sheets, the research team first mixed together an acid, a base and other ingredients for the hydrogel in a zip-top bag. Like vinegar meeting baking soda, this mixture released carbon dioxide bubbles within the gel, creating a porous and foam-like material. Next, the zip-top bag was sandwiched between glass slabs to form a sheet and then exposed to UV light, which sets the liquid around the bubbles, leaving pores behind.
Lastly, the team dipped the set sheet in alcohol and glycerol, and air-dried it. This caused the dried gel sheet to remain soft and flexible, with a similar texture to a fabric.
“To our knowledge, this is the first hydrogel that has been reported to have such tactile and mechanical properties,” says Raghavan. The gel sheets also stayed soft and flexible in ambient conditions for a year, indicating stability. “We are trying to achieve some unique properties with simple starting materials.”
Compared to a commercial cloth pad and a paper towel, a gel sheet the same size can absorb more than three times the amount of liquid. When researchers placed the gel sheet over 25mL of spilled water, the sheet swelled and soaked it up within 20 seconds, holding the water without dripping. In contrast, the cloth pad only absorbed about 60% of the water, leaving drips behind.
The gel sheet also performed well with thick liquids such as syrup, blood and even fluids that are a million times thicker than water. The researchers found that the gel sheet could absorb nearly 40mL of blood within 60 seconds, while a gauze dressing only soaked up 55% of the blood. The gel sheet also holds the blood well, whereas it trickles out of the blood-soaked gauze. Compared with sanitary pads, sponges and gauze, the gel sheet absorbed over two times more blood.
Next, the team plans to optimize their gel sheets by increasing their absorbency, strengthening them, lowering the cost and making them reusable. The researchers are also looking to develop gel sheets for absorbing oil.
“In principle, the gel sheets could be a superior form of paper towels,” says Raghavan. He envisions the gel sheets picking up spills in kitchens and laboratories, as well as cleaning up blood from surgeries and menstrual bleeding. Because of their flexible and absorbent nature, gel sheets also have potential for use as a dressing to stop bleeding from severe wounds. “I’m always interested in taking our inventions further than just publishing a paper. It would be wonderful to take it to actual practical use.”
This story is adapted from material from Cell Press, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.