Abstract
Low viscosity fluids could provide reliable lubrication for certain microelectromechanical system’s (MEMS) applications where high-sliding speeds and/or high sliding distances occur. However, while the use of low viscosity fluids leads to reduced hydrodynamic friction, high boundary friction can be a significant issue at low entrainment speeds. This article describes a series of tests of low viscosity fluids, blended with a friction modifier additive so as to provide a combination of both low hydrodynamic and low boundary friction at MEMS scales. The low viscosity fluids tested were hexadecane, low viscosity silicone oil, toluene and water. With the exception of water, the addition of the organic friction modifier octadecylamine to all these lubricating fluids produced a significant reduction in boundary friction. For a MEMS contact lubricated with silicone oil for instance, boundary friction was reduced from 0.5 to close to 0.05. The presence of the amine dissolved in the toluene had the effect of reducing boundary friction from 0.75 to 0.55; this was further reduced to 0.25 after the specimens had been immersed in the toluene-additive blend for 48 h. A water-soluble additive, diethylamine, was added to de-ionized water, at 0.1% by weight concentration. Although an initial reduction in boundary friction was observed (0.45–0.25), under these conditions the rapid onset of severe wear negated these effects. It is suggested that corrosion of silicon by water, followed by abrasion, is the cause of this accelerated wear.
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Acknowledgments
The financial support of the UK Engineering and Physical Sciences Research Council (EPSRC) under Grant No. EP/D04099X is gratefully acknowledged. The authors also wish to thank Mr. Robert J. Hergert of the Optical and Semiconductor Devices Group at Imperial College for his help with the design and fabrication of the test devices used in this work, and other members of the Optical and Semiconductor Devices and Tribology Groups at Imperial College for their assistance.
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Reddyhoff, T., Ku, I.S.Y., Holmes, A.S. et al. Friction Modifier Behaviour in Lubricated MEMS Devices. Tribol Lett 41, 239–246 (2011). https://doi.org/10.1007/s11249-010-9704-3
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DOI: https://doi.org/10.1007/s11249-010-9704-3