A Scratched Coating Heals Itself

A collaboration between the University of Fribourg, Case Western Reserve University and the US Army Research Laboratory

FRIBOURG – Your six-year-old found a nail in the garage and drew pictures across the side of your new car.

Gnash your teeth now, but researchers at the Adolphe Merkle Institute of the University of Fribourg, Switzerland, say the fix-up may be cheap and easy to do yourself in the not-too-distant future. Together with partners in the USA, they have developed a polymer-based material that can heal itself when placed under ultraviolet light for less than a minute. Their findings are published in the April 21st issue of Nature.

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Artist’s illustration of the concept of healable polymers. The new polymers developed by the CWRU/AMI/ARL team mimic the unique feature of biological tissues of being repairable. Unlike human skin, the new polymers don’t need stitches though. The researchers have shown that the combination of supramolecular polymers with a light-heat conversion scheme is a particularly effective approach to healable materials. Picture courtesy Dominique Bersier and Gina Fiore for the Adolphe Merkle Institute, Case Western Reserve University, US Army Research Laboratory.

 

Picture of a thin film of a new metallo-supramolecular polymer developed by the CWRU/AMI/ARL team. A portion of the deliberately introduced scratch across the film was healed by exposure to ultraviolet light. Pictures courtesy Gina Fiore for the Adolphe Merkle Institute, Case Western Reserve University, US Army Research Laboratory.

 

Schematic representations of the optical healing of the new metallo-supramolecular polymers developed by the CWRU/AMI/ARL team. Where irradiated with ultraviolet light, the originally solid material is liquefied and can quickly fill up cracks. After the light is switched off, the material solidifies and the original properties are restored. Schematic courtesy Marc Pauchard for the Adolphe Merkle Institute, Case Western Reserve University, US Army Research Laboratory.

 

Schematic representation of the molecular design of the new metallo-supramolecular polymers developed by the CWRU/AMI/ARL team. The new materials were created by a mechanism known as supramolecular assembly: comparably short, string-like molecules (green) with sticky end groups (blue) are assembled into much longer chains using metal ions (grey) as “molecular glue”. In this state, the materials behave in many ways like normal polymers. Upon irradiation with ultraviolet light, the structures are temporarily disassembled. This transforms the originally solid material into a liquid that flows easily. When the light is switched off, the structures re-assemble and the original properties are restored. Schematic courtesy Gina Fiore for the Adolphe Merkle Institute, Case Western Reserve University, US Army Research Laboratory.

 

Picture showing the healing procedure in the laboratory.

 

 

The animation, introduced and narrated by Prof. Stuart Rowan of Case Western Reserve University, shows the supramolecular polymerization and the optical self-healing of an intentionally damaged metallosupramolecular polymer developed by the CWRU/AMI/ARL team. The materials were prepared by combining functional polymers (blue) with metal ions (gray) to form a network. Upon damage with a knife, the metal-polymer bonds break, and when exposed to UV-light the material locally undergoes a rearrangement and then re-engagement of the broken bonds. After the light is turned off, the material solidifies and the self-healing process is complete. Animation courtesy Case Western Reserve University.

 

The animation, introduced and narrated by Prof. Stuart Rowan of Case Western Reserve University, shows the light-induced healing of one of the new metallo-supramolecular polymers developed by the CWRU/AMI/ARL team. Shown is a damaged film before, during, and after exposure to ultraviolet light focused on the center of the film, demonstrating the localized healing of metallo-supramolecular polymers. Movie courtesy Mark Burnworth for Case Western Reserve University, Adolphe Merkle Institute, US Army Research Laboratory, Nature.


Snapshots from the movie, showing the scratched sample strip (upper left), the ignition of the UV-lamp (upper right), the healing under UV-illumination (lower left) and the healed sample (lower right). Pictures courtesy Mark Burnworth for Case Western Reserve University, Adolphe Merkle Institute, US Army Research Laboratory, Nature.

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