Adding heat to a fold in a single layer of graphene spontaneously induces sliding, folding, peeling and tearing of the graphene into a strip, finds a study published in Nature this week. This is a newly observed behaviour for single layers of graphene, a substance already known for its unusual properties.
The effects of temperature on graphene sheets, which include the production of wrinkles, have been studied in the past in order to better understand the properties of graphene, such as its remarkable stability.
James Annett and Graham Cross produced two-dimensional graphene ribbons 300 to 2,000 nanometres in width and up to 5 micrometres in length from larger graphene sheets. The ribbons were observed to spontaneously grow following nucleation triggered by indentations made in the graphene sheets. The authors analysed the behaviour of the ribbons both at room temperature and when heated on a hot plate or using a focused laser spot, and observed that heating resulted in accelerated and expanded growth. Using a fracture-mechanics model, they interpret their observations as resulting from a thermodynamic mechanism whereby isolated, two-dimensional matter tends to coalesce towards a lower-energy, three-dimensional form.
These results may open up potential new uses for two-dimensional materials. In particular, this new self-assembly mechanism may be useful in turning two-dimensional materials into complex three-dimensional architectures, the authors suggest.