Getting glue to stick in dry conditions is relatively easy, but having it maintain a bond underwater is much more difficult. That said, a new bio-based glue not only works underwater, it actually gets stronger when immersed.
The nontoxic adhesive is being developed by Assoc. Prof. Gudrun Schmidt and colleagues at Indiana’s Purdue University. It’s made mainly of zein – which is a protein extracted from corn – and tannic acid, which is obtained from galls in oak tree bark.
When the glue is sandwiched between two objects which are subsequently placed underwater, a thin skin initially forms on it. That skin can be broken simply by piercing it with a finger or something similarly pokey. The surrounding water is then able to get into the glue, increasing its bond strength. Maximum bonding takes place at a water temperature of about 30 ºC (86 ºF).
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