New hydrogel sheets could one day replace paper towels

The paper-thin material can absorb more than 100 times its weight in water.
Hand wiping up liquid spill on table with a paper towel

The sheets also could be handy for biohazards and other toxic spills. Deposit Photos

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For all their utility and ubiquity (not to mention TV commercials’ allegations), paper towels are simply not very good at their job—at least when compared with hydrogels, which are already utilized in the form of microbeads between fabric or paper sheets for products like diapers or tampons. These materials, composed of large, interlocking polymers, absorb upwards of 100 times their weight in water, making them roughly 30 percent more effective than porous options like paper towels. 

Once used, however, hydrogels tend to become brittle and deteriorate after redrying, making them inefficient and often cost prohibitive for everyday use(actual sheets of the polymers have previously been generally too labor-intensive and difficult to manufacture). If one could combine the best of both worlds, everyday cleanups—not to mention medical or hazardous situations—could become a lot more manageable and simplified.

According to a new study published earlier this month in the scientific journal Matter, researchers at the University of Maryland are doing just that. Their own new quicker(er) picker-upper is made from a novel form of hydrogel that can be folded and cut with scissors much like paper, but is capable of absorbing three times the amount of liquid as common household materials. 

“To our knowledge, this is the first hydrogel that has been reported to have such tactile and mechanical properties. We are trying to achieve some unique properties with simple starting materials,” the research paper’s co-author, Srinivasa Raghavan, said in an announcement.

[Related: Watch this penny-sized soft robot paddle with hydrogel fins.]

Appropriately, Raghavan and their group relied in part on another common household kitchen item—zip-top bags—to help craft their new tool. First, an acid, base, and other ingredients to make the hydrogel were combined in storage bags. From there, the mix generated carbon dioxide in the gel. The bag was then placed between glass and subsequently exposed to UV light to set the gel around the bubbles, making it much more porous. The new sheet was finally submerged in glycerol and alcohol, then dried to become as pliant as normal fabrics, but capable of expanding as it absorbed and retained liquid.

In test comparisons, their gel sheet was able to absorb over 25 ml of water within just 20 seconds, while a cloth pad only managed 60 percent of the same amount of liquid. Researchers also tested their hydrogel on 40 mL blood, which it absorbed almost entirely within 60 seconds, compared to gauze managing only 55 percent.

If available to the public, the material could help in countless scenarios, from everyday chores to hazardous or toxic liquid cleanups. Unfortunately, the team’s new hydrogel sheet won’t be stocked on store shelves anytime soon—they would still be out of most consumers’ price range, and they remain non-reusable for the time being. Raghavan’s team next hopes to work towards lowering overall costs, increasing absorbency even more, making them able to withstand multiple uses, as well as capable of even absorbing oil.