Contact Pressure~up to [N/m 2 ] Operational speeds ~10 -3 to [m/s] Contact size ~10 -6 to [m] Film size ~10 -9 to [m] Engineering Dynamics multi-scale integrated approach Inertial Dynamics Contact Mechanics Tribology Surface Engineering Elasto-dynamics Unique Solution Local Interactions Global Interactions The model must be optimised to run across the physical scale

System Dynamics at Nano-Scale: Solvation/Hydration: Molecular reordering due to constraining effect of solid boundaries. Van der Waals Interactions: Intermolecular attractions between fluid-fluid and fluid-solid molecules. Electrostatic Repulsion: Repulsive action between the aforementioned. Meniscus Forces: Negative Laplace Pressure between adjacent solids due to wetness. Adhesion: attractive force at close range due to free surface energy. Drainage from contact does not conform to continuity of flow Other kinetics than hydrodynamics A combination of the above operate, depending on free surface energy, topography and physical chemistry

Nano-scale Lubrication and Tribology The approaching of a roller against a molecularly smooth surfaces elastic solid Intervening fluid: Octamethylcyclotetrasiloxane (OMCTS) (nonpolar). Prevailing interactions: Hydrodynamics Solvation micro-scale deformation Van der Waals M. Teodorescu, S. Balakrishnan and H. Rahnejat: “Physics of ultra-thin surface films on molecularly smooth surfaces” Proceedings of the Institution of Mechanical Engineers (IMechE), Journal of nano-Technology - Part N. Vol. 220 (1), 2006, pp 7-19.

FLY HEIGHT Load Motion

Coating: Octyldecyltrichlorosilane self- assembled monolayer (OTS-SAM) Prevailing interactions: Adhesive forces micro-scale Elastic deformation Bounce of a roller on rough surfaces coated with a SAM (MEMS application) Impulsive characteristics of rough elastic silica surface M. Teodorescu and H. Rahnejat: “Dry and Wet nano-Scale Impact Dynamics of Rough Surfaces with or without a Self-Assembled Mono-Layer”: Proceedings of the Institution of Mechanical Engineers (IMechE), Journal of nano-Technology - Part N. (in review)  for Si on Si impacts

Micro-impact dynamics of MEMS gears S. Theodossiades, M. Teodorescu and H. Rahnejat: “Micro-impact dynamics of MEMS gears with rough elastic and SAM protected conjunctions”, IEEE/ASME, Journal of Microelectromechanical Systems (in review) One cycle of the angular velocity of the gear under steady state condition With SAM With damaged (worn-off) SAM Several cycles of the angular velocity of the gear with complete SAM and with damaged SAM Power spectral density of the gear rotational velocity

Kinetic balance in nano- biotribological contact of gecko feet’s spatulae M. Teodorescu, H. Rahnejat: “Kinetic balance in nano-biotribological contact of gecko feet’s spatulae”: Proceedings of the Institution of Mechanical Engineers (IMechE), Journal of nano-Technology - Part N. (in review)

Analysis of basic biological locomotion element in nano-scale adhesion and detachment M. Teodorescu and H. Rahnejat: ”Mechanics of detachment and nano-scale friction for gecko’s feet spatula” M. Teodorescu and H. Rahnejat: ”Analysis of basic biological locomotion element in nano-scale adhesion and detachment” The 6th ASME International Conference on Multi-body Systems, Nonlinear Dynamics and Control, September 4-7, 2007 Las Vegas, NV, USA

Contact mechanics of layered solids: Contact pressures and deflections for the different values of  and d=5 Top surface and Layer-subsurface interface deformations (  =2 and d =5) M. Teodorescu, H. Rahnejat, R. Gohar, D. Dowson: “Harmonic Decomposition Analysis of Contact Mechanics of Bonded Layered Elastic Solids”: M. Teodorescu, H. Rahnejat, R. Gohar, D. Dowson: “Harmonic Decomposition Analysis of Contact Mechanics of Bonded Layered Elastic Solids”: Applied Mathematical Modelling. Elsevier Science. (in review) Sub-surface stress field  =1/2 and d =1

 1 /P Hertz [-] Sub-surface stress field for an uncoated tappet Sub-surface stress field for a tappet coated with a layer of 5mm DLC Subsurface stress field Deformed profile

Transient Elastohydrynamic Tribology: Elastohydrodynamic (EHL) Entrainment Velocity Subsurface Stress fields Neglecting Friction Considering Friction M. Teodorescu, M. Kushwaha, H.Rahnejat and S. Rothberg: “Multi-Physics Analysis of Valve Train Systems: From System Level to Micro-scale Interactions”. Proceedings of the Institution of Mechanical Engineers (IMechE), Journal of Multi-Body Dynamics - Part K. (in press) Vol. 221 (3) 2007