Researchers at the National University of Singapore (NUS) have produced a low cost, quick, and environmentally-friendly method of using cotton-based fabric waste – such as discarded clothing – and turning it into highly compressible and ultralight cotton aerogels with a variety of applications.
Among the lightest materials in the world, aerogels are highly porous with a substantial absorption capacity and low thermal conductivity. Such characteristics make them fit for use in oil-spill cleanups, personal care products such as nappies, and for heat and sound applications. NUS researchers have also recently shown them to be effective in controlling hemorrhaging and keeping military water bottles cold.
A rapid loss of blood – caused by a deeply penetrating wound or gunshot for example – can be life-threatening. Syringes filled with small capsules of cellulose sponge coated with chitosan - a natural agent derived from the shells of crustaceans which promotes blood clotting – are currently used to control hemorrhaging. The syringe is placed inside the wound and the capsule expelled where it expands and puts internal pressure on the injury to stop blood flow.
NUS researchers have developed a compressible hybrid cotton aerogel pellet which is more efficient for deep hemorrhagic wounds and is proven to overcome the slow expansion and absorption rates associated with current hemorrhage control devices.
The pellets consist of an optimal mix of cotton and aerogel, covered in chitosan – they are simple and cost-effective to produce, and can easily be used as a hemorrhage control device when incorporated into a clinical syringe. They can be safely used for treatment as the pellets are biocompatible.
Each cotton aerogel pellet can expand to 16 times its size in 4.5 seconds – larger and more than three times faster than existing cellulose-based sponges – while retaining their structural integrity. The unique morphology of the cotton aerogels allows for a larger absorption capacity, while the compressible nature enables the material to expand faster to exert pressure on the wound.
Associate Professor Hai Minh Duong, Department of Mechanical Engineering in the Faculty of Engineering
A cotton aerogel has also been incorporated into a light-weight thermal jacket which can be used by the military. Essential to a soldier’s survival kit is their canteen, a bottle carrying fluid necessary for hydration and heat-related injuries. A canteen can typically keep a liter of water cool for about 30 minutes, but this new jacket allows an ice slurry – crushed ice and liquid water – to be kept at 0.1 to 1°C for more than four hours.
The jacket – which comprises of a cotton aerogel layer embedded in commonly used fabrics – weighs about 200g, and provides better heat insulation performance compared to commercial insulated water bottles.
The heat insulation property of the novel cotton aerogels can be applied to various consumer products, such as cooler bags to keep food items fresh. We also foresee tremendous potential for other high-value applications, such as pipeline insulation and transportation of liquefied natural gas which needs to be stored at a low temperature.
Professor Nhan Phan-Thien
The team found the cotton aerogels can be easily compressed and that they quickly recover up to 97% of their original size when put in water.
This new eco-friendly cotton aerogel is a major improvement from the aerogel that our team had previously developed using paper waste. It is highly compressible, hence storage and transportation costs could be greatly reduced. Furthermore, these cotton aerogels can be fabricated within eight hours – this is nine times faster than our earlier invention and about 20 times faster than current commercial fabrication processes. They are also stronger, making them more suitable for mass production. While we have demonstrated novel application of the cotton aerogels for effective hemorrhage control and heat insulation, we will continue to explore new functions for this advanced material.
Associate Professor Hai Minh Duong
The team is hoping to work with companies to commercialize the knowledge and have filed a patent for their novel cotton aerogels.
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