Aerogel is usually the preserve of expensive laboratory experiments — but what if you could make it from garbage? Now, a team of researchers has developed a technique to turn scrap paper into an incredibly light, highly insulating super material. Most aerogels in the past have been made from silica, though versions made from materials like graphene and gold also exist. Either way, to produce an aerogel, you take a normal gel and then — very slowly and carefully — remove the liquid, leaving behind just the solid structure. The result is a substance that looks like the original gel but feels oddly empty to the touch, providing a lightweight material that's an excellent insulator of heat and surprisingly strong, too.
Now, a team of scientists from the National University of Singapore has developed a technique that uses cellulose to create an aerogel — which means it can be manufactured from waste paper. The process is surprisingly simple: mulch paper with water to release cellulose fibres, add more water and a cross-linking polymer resin, then agitate the mixture using high frequency sound. The resulting... slop is then frozen at -18C for 24 hours, freeze-dried at -98C for two days, and cured in an oven at 120C for three hours. Those processes evacuate the material of all its water.
Bingo: cellulose aerogel. The resulting opaque material is highly porous — in fact its 98.2 per cent air — as well as being flexible and fairly strong. When it's coated with methyltrimethoxysilane it becomes hydrophobic too, which allows its porous nature to soak up oil from water without becoming water-logged. It will actually soak up as much as 90 times its dry weight in crude oil, and 99 per cent of that oil can then be wrung out so that the material can be re-used.
The team reckons it could be used for more applications, though: Incredibly effective home insulation, protective packaging, winter clothing or even the absorbent layer in nappies, if the methyltrimethoxysilane is left out. The research has now been spun out into a separate company called Bronx MRC — though it's so far unclear how long it will be before the material becomes a commercial reality.
Image by Bronx MRC