Friction reduction in low-load hydrodynamic lubrication with a hydrophobic surface

A novel tribometer capable of measuring low friction forces and low loads at high speeds has been employed to measure the friction coefficient in a pure sliding, ball-on-flat contact in hydrodynamic lubrication conditions. The tribometer was custom-built for measuring friction at low loads, to allow...

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Bibliographic Details
Published in:Tribology international 2007-02, Vol.40 (2), p.154-159
Main Authors: Choo, J.H., Spikes, H.A., Ratoi, M., Glovnea, R., Forrest, A.
Format: Article
Language:English
Subjects:
Applied sciences
Exact sciences and technology
Friction measurement
Friction, wear, lubrication
Fundamental areas of phenomenology (including applications)
Hydrodynamic lubrication
Hydrophobic coating
Instruments, apparatus, components and techniques common to several branches of physics and astronomy
Machine components
Mechanical contact (friction...)
Mechanical engineering. Machine design
Mechanical instruments, equipment and techniques
Micromechanical devices and systems
Physics
Solid mechanics
Structural and continuum mechanics
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Summary:A novel tribometer capable of measuring low friction forces and low loads at high speeds has been employed to measure the friction coefficient in a pure sliding, ball-on-flat contact in hydrodynamic lubrication conditions. The tribometer was custom-built for measuring friction at low loads, to allow the authors to investigate the feasibility of using the liquid-slip phenomenon for the lubrication of high-sliding MEMS. The theory behind lubrication with liquid slip and its effect on friction is briefly discussed. Contacting surfaces were treated to create hydrophobic/hydrophilic or hydrophilic/hydrophilic pairs. Hydrophobic surfaces were made by coating mica with a self-assembled silane monolayer while the hydrophilic surfaces used were freshly cleaved mica and plasma-cleaned steel. Experiments were conducted at sliding speeds of up to 2 m/s and loads below 0.2 N. An aqueous glycerol solution was used as lubricant. Results obtained with hydrophilic/hydrophilic surfaces were in accord with hydrodynamic lubrication theory. Tests with hydrophobic/hydrophilic surfaces revealed a reduction in friction, which may be attributed to lubricant slip against the hydrophobic surface.
ISSN:0301-679X
1879-2464
DOI:10.1016/j.triboint.2005.09.006