Nonlinear Viscous Water at Nanoporous Two-Dimensional Interfaces Resists High-Speed Flow through Cooperativity

Abstract

Recently emerging ultrathin two-dimensional carbon materials provide potentially game-changing membranes for water filtration. Here we discover a changed water behavior at the nanoscale that is significantly distinct from its bulk state as water flows through two-dimensional carbon allotropes. We find that water exhibits a very high viscosity due to the cooperativity of water molecules that enhances the nonbonded H-bond interactions with the dense lattice of carbon structures, which renders flow significantly more viscous, with a resistance that is inversely proportional to the sixth power of the characteristic length of the nanopores. This is in contrast to a constant value as assumed in conventional knowledge. Our findings reveal how water molecules behave drastically different from their bulk state under extreme nanoconfinement conditions. These insights enable us to incorporate the size analysis of particles in variant untreated water into membrane design and propose the design of more efficient devices with higher filtration throughput and greater mechanical resilience.

Molecular Modeling and Mechanics of Acrylic Adhesives on a Graphene Substrate with Roughness

“…2g), as the first density peak corresponds to an H bond density that is more than four times than that of its bulk state. The singularity of mass and H bond distributions agrees with what has been observed for water at the interfaces with other nanomaterials [29][30][31][32]. In previous studies, it has been shown that a graphene substrate can lead to crystallization of polymer at the interface [33,34] and thus yields enhanced mechanics at the interface [35].…”

Structure and Transport Properties of Water and Hydrated Ions in Nano‐Confined Channels

“…In nanochannels, the water density and structure in the interfacial region varied with the wettability. [85] As a result, the water viscosity in the near-wall region is smaller than the bulk water viscosity with hydrophobic walls and larger than the bulk water viscosity with hydrophilic walls. Water structure and density distribution within different sizes of CNTs from which we can see that water structure transforms from ordered to unordered when the channel size gradually increases.…”

“…[46] Copyright 2018, Elsevier B.V. that under stronger interaction with the wall, the water molecules are inclined to form denser hydrogen bonding network and therefore to form more ordered and stable structures. [85] As a result, the water viscosity in the near-wall region is smaller than the bulk water viscosity with hydrophobic walls and larger than the bulk water viscosity with hydrophilic walls. [83] As stated by Itsuo et al, [86] when the average density increases, the atomic density profile of water inside CNTs become sharper, the peaks shift closer to the wall, and there may be a new peak of density appearing between the outermost and second layers.…”

Effect of critical thickness on nanoconfined water fluidity: review, communication, and inspiration

“…Based on the previous experiments and molecular dynamic simulations (Raviv et al 2001;Thomas and McGaughey 2008;Kelly et al 2015;Qin and Buehler 2015;Wei et al 2014;Haria et al 2013;Babu and Sathian 2011;Ye et al 2011;Zhang et al 2011;Petravic and Harrowell 2009;Chen et al 2008;Liu et al 2005), a quadratic equation is proposed to reveal the relationship between the viscosity ratio ( i ∞ ) and contact angle, as shown in the following equation: Wu et al (2017) proposed a linear equation to model the relationship between the viscosity ratio ( i ∞ ) and contact angle. While their equation fitted well with experiments and molecular dynamic simulations, the linear relationship may neglect some underlining physics that is still not well understood at present.…”

“…(3) that the water viscosity near the wall surface increases with decreasing contact angle. This is because the structure of hydrogen bonding network becomes strong with increasing interaction from nanopore wall (Qin and Buehler 2015). Besides, the water viscosity in the surface region can be larger or smaller than bulk water depending on hydrophilic (Kelly et al 2015;Wei et al 2014;Haria et al 2013) or hydrophobic (Petravic and Harrowell 2009).…”