Material self-heals at room temperature and can stretch to 10,000% original size - Uses for artificial muscles

04/20/2016 - 16:22

Carrie Kirby and Tom Abate

If there’s such a thing as an experiment that goes too well, a recent effort in the lab of Stanford chemical engineering Professor Zhenan Bao might fit the bill.

One of her team members, Cheng-Hui Li, wanted to test the stretchiness of a rubberlike type of plastic known as an elastomer that he had just synthesized. Such materials can normally be stretched two or three times their original length and spring back to original size.


Ref: A highly stretchable autonomous self-healing elastomer. Nature Chemistry (18 April 2016) | DOI: 10.1038/nchem.2492


It is a challenge to synthesize materials that possess the properties of biological muscles—strong, elastic and capable of self-healing. Herein we report a network of poly(dimethylsiloxane) polymer chains crosslinked by coordination complexes that combines high stretchability, high dielectric strength, autonomous self-healing and mechanical actuation. The healing process can take place at a temperature as low as −20 °C and is not significantly affected by surface ageing and moisture. The crosslinking complexes used consist of 2,6-pyridinedicarboxamide ligands that coordinate to Fe(III) centres through three different interactions: a strong pyridyl–iron one, and two weaker carboxamido–iron ones through both the nitrogen and oxygen atoms of the carboxamide groups. As a result, the iron–ligand bonds can readily break and re-form while the iron centres still remain attached to the ligands through the stronger interaction with the pyridyl ring, which enables reversible unfolding and refolding of the chains. We hypothesize that this behaviour supports the high stretchability and self-healing capability of the material.