Ultra thin films are built to disappear

Scientists at the University of Illinois have fabricated ultra-thin organic films that can be stacked together and ‘erased’ by environmental stimuli.

The multi-layered erasable polymer could have applications in fields as diverse as medicine and materials science.

‘We specifically designed this material so that when it is placed in the desired environment, it would readily dissolve and release embedded agents such as drugs,’ said Steve Granick, professor of materials science at the University of Illinois and a researcher at the Frederick Seitz Materials Research Laboratory.

To make the erasable material, Granick and a colleague built up layers of thin films of alternating polymeric acids and bases on a germanium crystal.

The films could, said Granick, also be deposited on other materials, such as glass; mica or teflon. Foreign compounds can then be added to the layers as they are formed.

‘By adding additional layers, we not only increase the amount of the embedded compound, we also make the material more stable, robust and resistant to attack in unwanted environments,’ said Granick.

‘One unique aspect of the assembly process is reversibility,’ said Granick. ‘The resulting multi-layers can be selectively destroyed after they are created.’

The controlled destruction of the material can be initiated by a change in pH, the application of an external electric field or by a change in a surrounding salt concentration.

‘The release of an embedded compound occurs when the multilayer films are exposed to appropriate environmental conditions that erase them,’ Granick said. ‘A drug, for example, could be released in a patient’s stomach or at the site of a wound, depending on the desired pH.’

Similarly, an electronic sensor could release an embedded agent by applying an electric field and dissolving the material.

The work is said to be a long way from any practical application, but ‘the concept can be used to design the deliberate and controlled release of foreign agents that have been embedded within the material,’ concluded Granick.