Researchers at Trinity College Dublin invented a rubber-stamp printing method (GraFold) to introduce waves into graphene, in a simple and large-scale way. The printing process is done using computer modelling to show the behavior of the graphene films on the stamp and substrate, and the wavy graphene can be printed onto any type of surface allowing for more sophisticated investigations of its properties.
In this transfer printing process called GraFold, the excess graphene required for forming the folds is induced by using PDMS stamps with a relief pattern such that the graphene tension and adhesion is modulated across the stamp. The graphene is kept on a planar structure at first, then the supporting polymer is dissolved and the graphene layer can ease into the recessed patterns. The graphene inked stamp is then placed gently onto the destination substrate, and then the stamp is peeled away leaving the mechanically patterned graphene film attached to the substrate.
Advanced microscopy techniques are used to reveal the electronic and strain behavior of graphene that has been folded, as folding may transform graphene into complex shapes with new and distinct properties.
The scientists say that the GraFold technique can allow for other structures such as fold intersections and pleats, both of which have their own specific electronic behaviors in graphene. In their upcoming work, the scientists are hoping to show that folding of graphene can lead to bandgap opening, spin polarized currents, larger spin orbit coupling and hence magnetic interactions.
In 2011, Chinese scientists demonstrated how folded graphene nanoribbons can grant a stronger material.
Source: nanowerk