Gallium is a little-known metal that could soon have a new profile as a reversible adhesive. Research has demonstrated that small changes in the temperature of gallium can control whether it sticks or not.
The science is fairly straightforward. At around 30 degrees Celsius, gallium transforms from solid metal to a liquid state. If a small amount of liquid gallium is applied to two surfaces and the temperature is reduced to less than 30 degrees, the two objects will stick together. Researchers applied hot gallium on the tip of a cylindrical rod and brought the gallium into contact with different materials such as plastic, glass or other metals.
When the occasion arises to separate the items, the temperature of the gallium is increased and the two items can be pulled apart with the addition of a little force. Gallium works somewhat like hot glue, a popular material deployed in DIY, although gallium requires less heating and cooling and can be removed more easily and cleanly.
It also works on rough surfaces, which have always been a test for reversible adhesives. Gallium was tested on damp and irregular surfaces that have proved challenging to other adhesives. Gallium’s performance was slightly reduced by water, but it still performed strongly. The binding power of gallium and its accompanying reversibility were seen to be effective in a number of conditions and are linked to its temperature-driven transition from solid to liquid..
Gallium is versatile
Gallium does not occur in its free state in nature, and when extracted, it is a soft, silvery metal that is also used in semiconductors. Gallium has other uses, such as being a component of LED light bulbs. Because it requires processing, recovering the gallium is an important part of recycling LED bulbs, according to a report in The Guardian.
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The developments with gallium are exciting, and it is thought that it could have applications in many areas where a temporary adhesive is needed. The applications include moving delicate biological materials such as organs or tissues, pick and place procedures in industry, short-term wafer bonding, or even transfer printing.