New self-destructing materials may lead to vanishing ink

Scientists have created a new material that disintegrates itself at an appointed time, an advance that may pave the way for products like vanishing ink and molecules for drug delivery.
The secret behind self-destructing molecules is that they would require a tiny input of energy to stay in their useful form, without it they disintegrate, researchers said.
"A cell constantly needs nutrients and energy. Otherwise, it would just fall apart to its simple building blocks," said Job Boekhoven, from the Technical University of Munich in Germany.
The molecular structures life forms uses are always "out of equilibrium," meaning they require a constant influx of energy, such as from food, to keep functioning.

Without this energy, the molecules will eventually dissociate on their own and return to a simpler state, Boekhoven said.
Applying the same techniques the team created a few different types of materials that require energy input to stay in their current forms, which the scientists call supramolecular molecules.

The first material was a simple colloid made of tiny beads, each of which are just one per cent as big as the diameter of a human hair.
As fuel is added, the miniature beads assemble like a string of pearls, and they can be tuned to assemble and disassemble in a certain order and at certain times, researchers said.

They envision these materials being used to deliver drugs. For instance, certain drugs need to bypass stomach acid, so if they are timed to disassemble only after they have passed into the gut, they could protect drugs until they reach the desired location.
The team also tested a fluffy crystalline material that is normally see-through but becomes cloudy and opaque when a fuel is poured on top of them.
As the fuel is used up, dark spots become clear again. The team envisions this material being used as a completely erasable ink, researchers said.
"So, you can create a temporary message that erases with a predefined lifetime. A material like that could dramatically reduce the use of ordinary paper in things like bills, tickets and receipts," said Boekhoven.

The third material was formed from long fibres that self-assemble to form structures that could one day be used to anchor a tissue transplant in place until the body can take over; the material would then vanish, researchers said.
The study was published in the journal Nature Communications.