Intrinsic Friction Diodes at the Interfaces of Two-Dimensional Materials.

Area of Science:

• Materials Science
• Nanotechnology
• Tribology

Background:

• Conventional understanding treats nanoscale friction at pristine interfaces as symmetric, with equal resistive forces in forward and reverse sliding.
• Existing models do not fully account for directional asymmetry in friction at the nanoscale.

Purpose of the Study:

• To reveal and characterize the intrinsic nanoscale friction diode effect in two-dimensional (2D) material interfaces.
• To investigate the mechanisms behind friction asymmetry and explore methods for its amplification.
• To establish principles for designing novel tribological systems with directional energy dissipation.

Main Methods:

• Atomistic simulations were employed to study friction at interfaces of hexagonal boron nitride (h-BN)/h-BN, transition metal dichalcogenide (TMD)/TMD, and graphene/h-BN.
• Analysis focused on the potential energy surface during sliding along specific crystallographic axes.
• The influence of sliding velocity and temperature on dynamic pathway selection was investigated.

Main Results:

• An intrinsic nanoscale friction diode effect was observed in common 2D material interfaces, showing asymmetric friction for opposing sliding directions.
• The asymmetry arises from inherent differences in the sliding potential energy surface related to specific stacking configurations.
• Sliding velocity and temperature significantly amplify this asymmetry by influencing trajectory selection, by over an order of magnitude.

Conclusions:

• A fundamental principle for discovering and designing nanoscale friction diodes has been established.
• The findings provide new insights into directional energy dissipation mechanisms at the nanoscale.
• This research offers strategies for developing tunable, directionally responsive tribological systems.