Flexible cellulose aerogel to overcome brittlenessPublished on August 24th, 2010 | By: Peter Wray
The team, composed of scientists from the Department of Fibre and Polymer Technology, Royal Institute of Technology, Stockholm, Sweden, soaked cellulose in a metal compound solution and freeze-dried it, removing all the moisture and leaving behind an aerogel in the form of solid fibers. The resultant substance was flexible, unlike typical aerogels, and could also be formed into a flat piece of magnetic nanopaper that was capable of supporting extremely heavy weight.
Researchers who developed this cellulose aerogel believe that it could find its use in fuel cells and in the study of materials science.
By now, aerogels are sort of old news in the materials science community. Although current forms have many uses, this group of scientists decided that overcoming their characteristic stiffness could open up a whole new range of uses.
When looking for a material to use to circumvent the stiffness, the authors decided to try a type of cellulose. Researchers first soaked it in a solution of two metal compounds, iron sulfate and cobalt chloride. While the cellulose soaked, tiny nanoparticles of the metals would stick to the cellulose and remain even after drying, so it could be used as a magnet if desired. Then they freeze-dried the cellulose, leaving nothing but a web of pure, solid fibers. The gel is highly porous and mostly air at this point, and yet can still sustain much weight.
Once the cellulose was freeze dried into an aerogel, the researchers found it was capable of two different applications. One involved crushing most of the air out of it, resulting in a small, strong, flat piece of magnetic “nanopaper” that could support 400,000 pounds per square inch.
But, as a regular aerogel, its properties were still highly unusual: It was flexible and could bend in half and twist easily. Normally aerogels are brittle and fracture under too much force, but the cellulose version could stand twice as much strain as a regular aerogel.
The scientists found that they could also use the flexible aerogel as a tiny sponge. Because its volume was almost 99 percent air, it could absorb water and then be wrung out, while still retaining its shape and magnetic properties. A 60 milligram patch of aerogel could hold about a gram of water.
The very fine structure of cellulose aerogel will allow it to be used in tiny pieces while retaining their characteristics-very stiff and magnetic, or magnetic, flexible, and absorbent-depending on the properties needed.
The authors speculate that their aerogel could find wide use in materials science, as its components, especially the cellulose, come pretty cheap. In the future, they predict it will play the role of a tiny actuator, or appear in microfluidic devices used in fuel cells and for studying the physics of cells.
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