Researchers from the Michigan Technical University created an underwater smart glue prototype that can go from sticky to solid in seven seconds with a small application of electricity. The smart glue’s adhesion can be turned on and off, in the air and underwater. This research has promise for underwater glue, wound dressings, prosthetic attachments, making automotive parts, manufacturing and more.

A titanium sphere and a thin platinum wire act as electrodes to deliver a jolt of electricity to a catechol-containing adhesive. A Michigan Tech team has used electricity for the first time to deactivate a catechol-containing adhesive in salt water. Source: Sarah Bird/Michigan Tech

The new smart glue uses catechol. Catechols are synthetic compounds that mimic the wet-but-still-sticky proteins secreted by mussels. The team found that these compounds are promising for underwater adhesive. Catechol has been used in the past to mimic mussel and adhesive proteins, but this is the first time that electricity has been applied to deactivate it. The electricity method is more convenient than using pH, easier to integrate into electronics and enables detaching with the push of a button.

The most difficult part of this research was creating repeatable contact mechanics that can test and measure the smart glue’s adhesion before and after applying the jolt of electricity. The team built a titanium sphere with a platinum wire electrode that applies electrical stimulation to the adhesive in contact with the sphere in salty water. This method makes it easy to control the voltage that is applied through the water, glue and sphere. It also controls how salty the water is.

The current's running time is also important. The more time, voltage and salt that is applied, the more the catechol adhesives get oxidized and become less adhesive. With a strong voltage, the glue can detach in seven seconds. This also changes the glue’s color. The adhesive starts out as white, but after detaching it turns red.

A paper on the smart glue was published in the Journal of the American Chemical Society.