▎ 摘　　要

Droplet evaporation is a ubiquitous phenomenon with numerous applications. It plays a pivotal role in life and industry since it concerns heat transfer in high efficiency to reach a desired temperature. However, to rationally mediate evaporation has always been a significant challenge. Here by studying the interactions of water molecules with graphene-covered substrate, we propose that graphene could effectively affect water evaporation rate by changing the length of contact line. More importantly, evaporation per length of contact line before and after graphene coverage shows negligible change, suggesting graphene is transparent for evaporation (per unit contact length). Molecular dynamics simulations confirm experimental findings and indicate that principal evaporation events take place via single-molecule desorption at the contact line.