Tuning Water Slip Behavior in Nanochannels Using Self-Assembled Monolayers.

Area of Science:

• Surface Science
• Fluid Dynamics
• Computational Chemistry

Background:

• Water slip at solid surfaces is crucial for micro-/nanofluidic devices.
• Understanding molecular-level dynamics and mass transport at interfaces remains a challenge.

Purpose of the Study:

• Investigate water slip behavior on gold surfaces functionalized with self-assembled monolayers (SAMs).
• Analyze the impact of varying polar functional groups on interfacial water dynamics and slip.

Main Methods:

• Utilized nonequilibrium molecular dynamics (MD) simulations.
• Simulated water confined between gold surfaces modified with different SAMs.

Main Results:

• Observed a transition from positive to negative water slip with increasing surface hydrophilicity.
• Stronger water-SAM interactions on hydrophilic surfaces increased friction and local viscosity, impeding slip.
• More hydrophilic surfaces exhibited slower interfacial water relaxation and increased water trapping within the SAM layer.

Conclusions:

• Interfacial interactions and water trapping significantly influence water slip behavior.
• Findings offer insights into water slip at functionalized surfaces.
• Provides design guidelines for micro-/nanofluidic applications.