Super-absorbent towel soaks up liquids better than cloth or paper

A thin towel that expands into a jelly-like blob can absorb liquids three times as well as paper or cloth-based products.

Hydrogels – meshes of long molecules linked together in a network – can absorb and hold large quantities of water, but when they dry out, they become brittle and so aren’t suitable as paper towels.

Now, Srinivasa Raghavan at the University of Maryland and his colleagues have developed a method to produce a dry, absorbent hydrogel that stays intact even while rolled up.

To make the hydrogel sheets, the researchers combined vinegar and baking soda to produce a foam and placed it into a zip-lock bag. They then sandwiched this between glass plates and exposed it to ultraviolet light, before setting the sheet in glycerol and alcohol.

“What we did could have been done 30 or 40 years ago,” says Raghavan. “All the ingredients and technology were available.”

They then tested how well the sheet absorbed water compared with common kitchen towels and cloths, finding that it could absorb more than three times as much and didn’t drip or leave liquid behind.

The gel sheet can’t be reused, so would fail to compete with kitchen cloths on that front, but Raghavan sees it as a more readily available alternative to kitchen roll or single-use medical gauze. When the researchers compared it with gauze for absorbing blood, they found that the gel sheet could take up almost 40 millilitres, while the gauze could only absorb about half that amount.

While the production process is simple and could easily be scaled up, more work could be done to make the sheets more absorbent, says Raghavan.

The design of the sheet is original and it has impressive absorbent properties, says Alberto Saiani at the University of Manchester, UK. To compete with paper towels, though, it will need to be developed further to make it cost-effective and recyclable, he says.