Scientists find electrifying solution to sticky problem

NTU Assistant Professor Terry Steele
Scientists from Nanyang Technological University (NTU), Singapore have invented 'Voltaglue', an adhesive that hardens when a voltage is applied to it.

The scientists say that the glue could be used in applications including underwater pipe repairs and replacing sutures in surgery. The properties of the adhesive could also be tailored to be more gel-like or rubber-like which would work well in vibrating or damp environments.

Assistant Professor Terry Steele, the lead scientist for this research project from NTU's School of Materials Science and Engineering, said it took them over a year to develop an adhesive that could work under wet conditions such as in the human body or underwater.

"Most glues in the market don't work under wet conditions, much like how sticky tapes won't work if the surface is wet, since the adhesive will stick to the water instead of the surface," Steele said.

Usually adhesives such as superglue harden upon contact with moisture in the air. Others like epoxy have to be baked at around 150°C, or made using two different chemicals mixed together.

"We had to find a way to make glue which cures when we want it without being affected by the environmental conditions, so electricity was the best approach for us. The hardness of our glue can be adjusted by the amount of time we apply a voltage to it, which we call electrocuring."

This unique electrocuring property allows Voltaglue to be customised for different applications.

"For example, if we are gluing metal panels underwater, we want it hard enough to stick for a long time. However, for medical applications, we want the glue to be more rubber-like so it wouldn't cause any damage to the surrounding soft tissues," Steele explained.

Voltaglue is developed using hydrogels consisting of carbon molecules called carbenes grafted onto tree-shaped plastic known as dendrimers.

Upon contact with electricity, the reactive carbenes, which are capable of hooking onto any surface nearby, are released. The amount of 'hooks' created depends on how long electricity is applied and how many carbenes are present.

Steele is now furthering research into making the results reversible, aided by a competitive research grant of almost US$670,000 awarded by Singapore's Ministry of Education.

As the world becomes more concerned about sustainability, companies are looking to design 'End-of-Life' products that can be easily recycled, reused or remanufactured into new parts and components so as to reduce waste and energy consumption.

Glues which can cure and be subsequently un-cured through electricity would be the industry's 'Holy Grail', as automakers and shipyards will be able to assemble and dissemble parts, minimising the need for fixation by bolts, nuts and screws.

Such reversible glue will also open up new possibilities in the global adhesive market in transportation applications, estimated to be worth over US$3.3bn in 2016.

Author
Tom Austin-Morgan

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