Working group 3

The goal is to explore and understand the dynamical response of tribological systems sheared in confined geometries, where critical boundary-lubricated regimes and highly dissipative intermittent sliding may take place. An efficient control of friction in such systems represents a formidable challenge of great practical relevance for a broad class of nanotechnological devices.

Main objectives

  • Investigate the mechanisms of contact formation and energy dissipation in AFM in liquids.
  • Understand the relation between friction, adhesion, load, and number of molecular layers in ionic liquid lubricant films, and nanometer-thin polymer films.
  • Understand the flow behaviour of water and organic fluids in nanometrically bounded spaces, in particular inside carbon nanotubes, and probe the possibility of a superlubric behaviour.
  • Explore the transition from molecular to hydrodynamic behaviour.
  • Investigate the conditions for the possible generation of solitonic motion of a confined lubricant.
  • Address the potentiality of lamellar lubricants (graphite, MoS2,…) for creating superlubric interfaces.
  • Explore/compare friction dynamics of granular systems and colloids with that of confined fluid lubricants.

Methods A

Experimental: *SFA measurement of the shear stress between two atomically smooth surfaces across films of ionic liquids, while also controlling the number of molecular layers and applied load. *Design of a hierarchical macro to nanofluidic device with a single carbon nanotube as nanofluidic system. *Perform transport measurements using patch-clamp techniques and single-molecule fluorescence.

Methods B

Theoretical: *Combined ab-initio, classical MD simulations and potential of mean force calculations for grand canonical ensembles including single-asperity interactions with surfaces in liquids. *Large scale MD calculations to unravel the detailed tribological mechanisms which play a role in shearing confined thin polymer films. *Multi-scale techniques from density-functional theory (DFT) to force field MD to coarse-grained approaches.