Those little sachets of silica gel that come in everything from your shoeboxes to burrito packets are the gold standard for fending off fungal growth and moisture. Scientists have now developed a material they claim can absorb twice as much, with footwear that stays fresh by incorporating it into its soles one of the possible early applications.

At the heart of the new discovery is the much-hyped wonder material known as graphene. Scientists at Australia's University of New South Wales (UNSW) used a form of graphene called graphene-oxide, which consists of carbon, oxygen and hydrogen atoms and is made by treating graphite, the three dimensional form of graphene, with strong oxidizing agents.

This creates a laminate of layered material with extraordinary absorbing abilities that has previously been used to develop membranes that can separate salt from seawater, remove radioactive materials from water and slow release fertilizers.

In adapting it for use as a drying agent, the UNSW team carried out experiments designed to both better understand the material's adsorption and desorption capabilities, and see if they could tweak the design as a way of controlling moisture absorption.

Through these exercises, it found its material was able to soak up 0.58 g of water per gram of graphene oxide, and that its properties could be attributed to the high capillary pressure within the laminates and wrinkles that resemble tunnels on the material's surface. Furthermore, they found that by altering the space in between each layer of graphene oxide, they may be able to fine-tune the rate at which the material absorbs moisture.

This raises the prospect of a high-performing drying agent that can not only soak up moisture much more effectively than what is currently available, but one that can be fine-tuned during production to suit different applications.

This could see it put to use in electronics, packaging, air conditioners and footwear. And because it also discharges moisture at low temperatures compared to conventional drying agents, it can be dried out and used again at relatively low costs.

"One novel application we are investigating is the integration of the desiccant into inner soles of shoes to control odour and moisture," says Dr Rakesh Joshi of the UNSW School of Materials Science and Engineering. "As the moisture could be released back into the atmosphere using an ordinary household device like a warm oven, shoes could be recharged regularly to keep them constantly fresh."

The research was published in the journal Chemical Science.

Source: University of New South Wales