Characterizing the wetting behavior of 2D materials: a review

Abstract

A comprehensive understanding of the interaction between liquids and two-dimensional (2D) materials is pivotal for the manipulation, transfer, and assembly of 2D materials across a wide range of applications, from liquid cell microscopy to hydrovoltaics. This review discusses this interaction by surveying the intrinsic wettability of suspended 2D materials and the apparent wettability of substrate-supported 2D materials, both of which have recently been revealed through water contact angle (WCA) experiments. We discuss important factors that can affect the apparent WCA, including thin film elasticity, surface contamination, and the microstructure and electronic state of the underneath substrate. We also discuss some microscopic-level insights into the 2D material-liquid interface that have recently been provided via spectroscopy characterizations and surface energy measurements. By discussing the latest experimental advancements in characterizing the interaction between 2D materials and liquid droplets, this review aims to inspire future theoretical progress capable of unraveling the intricate and occasionally contradictory wetting behavior observed in 2D material systems.