It may sounder counter-intuitive, but adding drops of humble old water into solid materials can actually increase their strength and changes their other properties in interesting and useful ways.
Researchers from Yale have discovered that adding droplets of water into some solids can strengthen and stiffen them, by virtue of their surface tension. The force is often observed in fluids, and its role is typically to reduce the surfaces area of the material.
Embedding small droplets of water—each around a micron in size—into solids means they can make use of this force. It's a kind of restoring force, always attempting to keep the droplets as small as possible so in turn resisting extension—and stiffening the lump of water-infused material. Eric Dufresne, the researchers behind the work, explains to The Speaker:
"As the solid gets stiffer, the liquid droplets need to be smaller in order to have this stiffening or cloaking effect. By embedding the solid with droplets of different materials, one can give it new electrical, optical or mechanical properties. On the simple scale, they could lower the cost be replacing expensive polymers with simple liquids. More excitingly, embedded droplets could provide an electromagnetic handle to actuate structures."
So far, the team have shown that it works with silicone, making it up to 30 per cent stronger by adding water droplets. Obviously it still needs to be done with other materials, but this is certainly a neat and affordable method for tweak material properties. [Nature Physics via The Speaker]
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