A reusable sponge from the U.S. Department of Energy’s Argonne National Laboratory cleans up spills – not in the kitchen, but on the coast.

Using a technique called sequential infiltration synthesis (SIS), the lab researchers developed a unique nonporous structure – one chemically engineered to grab oil molecules from water.

By exposing to the foam to reaction-inducing, precursor chemicals, the SIS method creates a metal-oxide coating on the compressible material. The infused metallic atoms serve as a kind of glue for oil-loving, or oleophilic, molecules.

The result: The “Oleo” sponge.

The seat-cushion-sized foam block, funded originally by the U.S. Coast Guard and the Bureau of Safety and Environmental Enforcement, can be wrung out and used again and again.

In an early 2017 demonstration, the team traveled to the Leonardo, NJ-based National Oil Spill Response Research & Renewable Energy Test Facility, or Ohmsett. With the help of the agency’s giant seawater tank, the team’s Oleo sponge successfully collected diesel and crude oil from both below and on the water surface.

“The material is extremely sturdy,” said co-inventor and Argonne scientist Seth Darling at the time of the test. “We’ve run dozens to hundreds of tests, wringing it out each time, and we have yet to see it break down at all.”

Given the ability to fine-tune the sponge for specific chemicals, Darling and his fellow researchers, including Argonne chemist Jeff Elam and former Argonne post-doc Ed Berry, see the material someday supporting a range of applications.

Barry spoke with Tech Briefs about the origins of the Oleo sponge – and how the sponge could someday be tailored to pick up more than just oil.

Tech Briefs: What does the sponge look like?

Ed Barry: The sponge looks like a kind of handheld kitchen sponge.

If you take a closer look at a piece of foam, you’ll find a very porous microstructure. Certain versions of polyurethane foam are roughly 95-percent free volume. The goal for us is to fill up that empty space.

In the case of Oleo sponge, we’re able to fill it up, because we modify the chemistry of the surface and oil just slides in. We render it oleophilic, or oil-loving, and we’re able to fill this volume up with oil.

Tech Briefs: How do you make the sponge “oil-loving?”

Barry: In order to get things to go, flow, attach, or even absorb onto these polymeric filaments of the foam, you really need to engineer a type of chemistry into that foam.

The foam is exposed to a gas, and the gas contains precursors – chemicals that are going to end up functionalizing this foam. The foam that you buy off the shelf does not have a specificity for oil; you have to engineer that in. In the process of doing this SIS treatment, we introduce a chemical specificity for oil.

Tech Briefs: What is Sequential Infiltration Synthesis exactly, and how does the process introduce this kind of chemical specificity?

Barry: With Sequential Infiltration Synthesis, the idea is that you could selectively modify certain chemical groups and grow or attach inorganic components, with an almost atomic-layer precision.

In other words, if you’re trying to put a functionalized coating on a polymeric type substrate, you can now infiltrate your inorganic coding deep within the polymer.

Typically what happens is you’re growing, say, metallic oxide, and you can dial in the thickness you want, and literally grow up this material layer by layer.

Tech Briefs: How do you tailor the sponge to separate oil from water?

Barry: If you take a glass of water and pour oil in it, the oil does not separate. Oil will always like to be around oil, especially in a water-based environment. What we’re able to do is take a molecule that kind of looks like oil and chemically graft it, or tether it, onto the surface.

SIS is really the first step in getting a suitable binding site or coating on these polymeric strands on your foam, where you can engineer an oil-loving chemistry to it.

Tech Briefs: How much of this material is needed to address an average spill?

Barry: In the same way that you don’t need a mop that’s the size of your kitchen floor when you spill something, you don’t need [an enormous] sponge to absorb an entire area of an oil spill. But if an oil spill is not contained, because of a current or wave patterns, oil will be brought to places where it will be exceedingly hard to try to chase after.

Tech Briefs: How well does the Oleo sponge work?

Barry: The Coast Guard was really interested in oil absorption below the surface of the water.

Our materials are typically characterized in terms of absorption capacity: If I give you a gram of foam, how many grams of oil do you get back?

In our case, we have 30 grams per gram. So: If I give you a pound of foam, you’ll absorb 30 pounds of oil.

You get roughly a factor of 30. The best materials are on the order of, say, 100, however, ours is reusable. So, if you reuse it three times, you’re already close to a factor of 100.

Tech Briefs: What kind of labor is involved when using the sponge to address an oil spill?

Barry: There are different form factors and shapes that we’ve imagined with this foam. With wildlife covered in oil, we imagine that you can actually use it like a sponge and you actually sit there and scrub. And in the case of oil on the surface of water, you’re deploying pads – throwing it out, extracting it back, wringing it out, and throwing it back out again.

Tech Briefs: What’s next regarding development?

Barry: It has not been commercialized yet. We’ll pursue industrial partnerships. If we have a larger reactor size, we can process more foam at one particular moment, so that is a major emphasis looking ahead.

Tech Briefs: What is most exciting to you about what the Oleo sponge can do?

Barry: We can modify the chemistry, and we can potentially start to introduce other specificities, start to absorb other things, filter things, and use this as a separation material.

So, in this case it likes oil. But can you make it something that selectively absorbs just water in an oil-based environment? Or can you, for example, make a sponge that selectively absorbs only soap and leaves just the water?

Can you make a sponge that is actually able to selectively absorb nuclear-based components and contaminants, and effectively clean water streams? If the Oleo sponge in any way reached that sort of potential, that would be great.

What do you think? Share your questions and comments below. Will sponges help oil-spill remediation efforts?

Argonne postdoctoral researcher Ed Barry wrings out a sheet of Oleo Sponge during tests at Argonne. (Image Credit: Mark Lopez/Argonne National Laboratory)