The team found that a multigenerational approach – the application of several shrinking processes – could compress the graphene sheets to one-fortieth of their original size, as well as creating ‘interesting patterns’.
According to Dr Ian Wong, one of the researchers, the sequence of crumpling matters. He said: "It's not like multiplication where 2 x 3 is the same as 3 x 2. The material has a 'memory' and we get different results when we wrinkle or crumple in a different order."
The researchers generated a kind of taxonomy of structures born from different shrinking configurations. They then tested several of those structures to see how they altered the properties of the graphene sheets. One of the results showed that a highly crumpled graphene surface becomes superhydrophobic after three specific shrinks.
"You don't need a new material to do it," Dr Po-Yen Chen said. "You just need to crumple the graphene."
In additional to water resistant coatings, graphene compressed in this manner might also be useful in stretchable electronics, such as wearable sensors, as it also exhibits enhanced electrochemical properties, which could also make it useful as an electrode material in batteries and fuel cells.
The group plans to continue experimenting with different ways of generating structures on graphene and other nanomaterials.
"There are many new two-dimensional nanomaterials that have interesting properties, not just graphene," Dr Wong said. "So other materials or combinations of materials may also organise into interesting structures with unexpected functionalities."