Supercomputer models graphene-water interaction

Researchers at the New Jersey Institute of Technology (NJIT) used the Comet supercomputer at the San Diego Supercomputer Center (SDSC), located at the University of California San Diego, to create detailed simulations of graphene-water interactions, to determine if graphene is a good candidate for delivering medicine to a specific part of the body.

A simulation done using SDSC’s Comet supercomputer shows a cross-sectional view of seven graphene flakes in a water droplet, and that the multi-layered graphene eventually merges together. Credit: Solanky et al.

While graphene has been extensively studied for many years in water-based solutions, especially in the biomedical sciences field, researchers say they still need to better predict the surface traits of such two-dimensional materials when exposed to water or liquids containing water.

The findings describe in detail how graphene interacts with a droplet of water. One of the critical issues is how the graphene flakes behave when they are placed inside a water droplet, said Mechanical and Industrial Engineering Professor Dibakar Datta. Doing experiments to understand the graphene-water interaction is expensive and requires a great deal of labor, so to meet this challenge, we performed computer simulations to gain fundamental insight.

Researchers found that the graphene flake came out of the droplet to wrap it, as graphene is hydrophobic. There is a particular interest in graphene wrapping for nanocomposite materials, where the wrapped component can be nanoparticles, nanowires, bacteria, drugs that need to be administered and more. For drug delivery, graphene flakes and drugs can be placed inside the water droplet. Due to the hydrophobicity, all flakes come out and wrap the droplet containing drugs.

Upon the water drying, graphene flakes completely encapsulate the drug and act as a cargo for the drug-delivery applications. Moreover, depending on the arrangements, when multiple graphene flakes were placed inside a water droplet, all of the flakes tended to come out of the droplet and self-assemble, or clump together. This pattern of self-assembly depends upon the size of the water droplet and the geometry of the graphene flakes placed inside it.

The self-assembled graphene can be used for different graphene-based medical nanodevices. Specifically, these simulations showed that by tuning the geometry and the initial arrangement of graphene flakes inside the water droplet, medical personnel can utilize the final graphene wrapping or self-assembly for drug-delivery where a water medium is used, and other medical nanodevice applications.

We also studied how graphene flakes failed when placed inside the droplet, explained Datta. Graphene wrinkles to wrap around the water molecules, which means that it doesn’t undergo brittle or sudden breaking or fractures like graphene does in a non-water medium.