Abstract

Graphene is a two-dimensional (2D) carbon-based nano-material consisting of a single layer of carbon atoms in honeycomb shaped lattice. Graphene has gained worldwide attention due to its outstanding properties such as high mechanical strength [1], high thermal and electrical conductivity [2,3], chemical adjustability [4,5], and optical transparency [6]. For nanofluidic applications such as biotechnology (drug delivery, DNA sequencing, cancer detection, etc.), biosensing (detection of pathogens, measurement of clinical parameters, monitoring of environmental pollutants, etc.), nanolubrication, nanopumping, and nanofiltration, graphene has special importance as the channel material or semipermeable porous membrane that allows enhanced fluid flow rates and high selectivity. These valuable aspects are mainly associated with two unique properties of graphene [7]. First, graphene is hydrophobic. The interaction strength between water atoms is stronger than that of the water/carbon atoms, making water atoms recede from walls. As a result, water contact angle on a monolayer of graphene is in the range of 95 ^° –100 ^° , indicating a hydrophobic characteristic [8,9]. Second, due to four covalent bonds formed by each carbon atom in the graphene layer, the surface density of graphene is much higher than that of many other materials used in nanofluidic applications. These strong covalent bonds create smooth surfaces, resulting in a low surface potential corrugation. Consequently, liquids on graphene surfaces show weak interfacial friction and large slip, leading to high flow rates [10].