Tribology Letters

, Volume 49, Issue 1, pp 217–225 | Cite as

Hydrodynamic Friction Reduction in a MAC–Hexadecane Lubricated MEMS Contact

  • J. Y. Leong
  • T. Reddyhoff
  • S. K. Sinha
  • A. S. Holmes
  • H. A. Spikes
Original Paper


Recent research has shown that hydrodynamic lubrication is an effective means of reducing friction in high sliding micro-electromechanical systems (MEMS). At high speeds, however, such lubrication can lead to increased friction due to viscous drag. This article describes a series of hydrodynamic tests on a silicon MEMS contact lubricated with a blend of hexadecane and a multiply-alkylated cyclopentane (MAC). Results show that the presence of the MAC reduces hydrodynamic friction compared with neat hexadecane. Such behaviour is contrary to conventional hydrodynamic theory, since the viscosity of the MAC—a mixture of di- and tri-(2-octyldodecyl)-cyclopentane—is significantly higher than that of neat hexadecane. This effect increases with MAC concentration up to an optimum value of 3 wt%, where the hydrodynamic friction coefficient at 15,000 rpm is reduced from 0.5 to 0.3. Above this concentration, friction begins to rise due to the overriding effect of increasing viscosity. The viscosity of the blended lubricant increased monotonically with MAC concentration, when measured using both a Stabinger and an ultra-high shear viscometer. In addition to this, no reduction in friction was observed when a squalane–hexadecane blend of equal viscosity was tested. This suggests that some property of the MAC–hexadecane lubricant, other than its viscosity, is influencing hydrodynamic lubrication. A tentative explanation for this behaviour is that the MAC induces the liquid to slip, rather than shear, close to the silicon surfaces. This hypothesis is supported by the fact that the friction reducing ability of the MAC blend was inhibited by the inclusion of octadecylamine—a substance known to form films on silicon surfaces. Furthermore, the MAC reduces friction in the mixed regime, in a manner suggesting that the formation of a viscous boundary layer. This unusual behaviour may have useful implications for reducing hydrodynamic friction in liquid-lubricated MEMS devices.


MEMS Hydrodynamic lubrication Boundary lubrication Multiply-alkylated cyclopentanes Silicon 



This research was supported by the Singapore National Research Foundation under its Competitive Research Program (Award Number: NRF-CRP 2-2007-04). The views expressed herein are those of the authors and are not necessarily those of the Singapore National Research Foundation.


  1. 1.
    Syms, R.R.A., Zou, H., Stagg, J., Veladi, H.: Sliding-blade MEMS iris and variable optical attenuator. J. Micromech. Microeng. 14(12), 1700 (2004)CrossRefGoogle Scholar
  2. 2.
    Girbau, D., Pradell, L., Lazaro, A., Nebot, A.: Electrothermally actuated RF MEMS switches suspended on a low-resistivity substrate. J. Microelectromech. Syst. 16(5), 1061–1070 (2007)CrossRefGoogle Scholar
  3. 3.
    Chau, K.H.L., Sulouff, R.E.: Technology for the high-volume manufacturing of integrated surface-micromachined accelerometer products. Microelectron. J. (Inc. J. Semicust. ICs) 29(9), 579–586 (1998)Google Scholar
  4. 4.
    Velten, T., Ruf, H.H., Barrow, D., Aspragathos, N., Lazarou, P., Erik, J., Malek, C.K., Richter, M., Kruckow, J., Wackerle, M.: Packaging of bio-MEMS: strategies, technologies, and applications. IEEE Trans. Adv. Packag. 28(4), 533–546 (2005)CrossRefGoogle Scholar
  5. 5.
    Kim, S.H., Asay, D.B., Dugger, M.T.: Nanotribology and MEMS. Nano Today 2(5), 22–29 (2007)CrossRefGoogle Scholar
  6. 6.
    Maboudian, R., Ashurst, W.R., Carraro, C.: Self-assembled monolayers as anti-stiction coatings for MEMS: characteristics and recent developments. Sens. Actuators A Phys. 82(1–3), 219–223 (2000)CrossRefGoogle Scholar
  7. 7.
    Srinivasan, U., Foster, J.D., Habib, U., Howe, R.T., Maboudian, R., Senft, D.C., Dugger, M.T.: Lubrication of polysilicon micromechanisms with self-assembled monolayers. In: Conference on Solid State Sensor and Actuator Workshop, Hilton Head, 1 Jun 1998Google Scholar
  8. 8.
    Srinivasan, U., Houston, M.R., Rowe, R.T., Maboudian, R.: Self-assembled fluorocarbon films for enhanced stiction reduction. In: International Conference on Solid State Sensors and Actuators, TRANSDUCERS, Chicago (1997)Google Scholar
  9. 9.
    Smallwood, S.A., Eapen, K.C., Patton, S.T., Zabinski, J.S.: Performance results of MEMS coated with a conformal DLC. Wear 260(11‚Äì12), 1179–1189 (2006)CrossRefGoogle Scholar
  10. 10.
    Tagawa, M., Ikemura, M., Nakayama, Y., Ohmae, N.: Effect of water adsorption on microtribological properties of hydrogenated diamond-like carbon films. Tribol. Lett. 17(3), 575–580 (2004)CrossRefGoogle Scholar
  11. 11.
    Houston, M.R., Howe, R.T., Maboudian, R.: Effect of hydrogen termination on the work of adhesion between rough polycrystalline silicon surfaces. J. Appl. Phys. 81(8), 3474–3483 (1997)CrossRefGoogle Scholar
  12. 12.
    Asay, D., Dugger, M., Kim, S.: In situ vapor-phase lubrication of MEMS. Tribol. Lett. 29(1), 67–74 (2008)CrossRefGoogle Scholar
  13. 13.
    Ashurst, W.R., Carraro, C., Maboudian, R.: Vapor phase anti-stiction coatings for MEMS. IEEE Trans. Device Mater. Reliab. 3(4), 173–178 (2003)CrossRefGoogle Scholar
  14. 14.
    Potter, C.N.: Hermetic MEMS package and method of manufacture. U.S. Patent No. 7,358,106 B22005. Stellar MicroDevices, Inc., AustinGoogle Scholar
  15. 15.
    Asay, D.B., Dugger, M.T., Ohlhausen, J.A., Kim, S.H.: Macro- to nanoscale wear prevention via molecular adsorption. Langmuir 24(1), 155–159 (2007)CrossRefGoogle Scholar
  16. 16.
    Ku, I.S.Y., Reddyhoff, T., Holmes, A.S., Spikes, H.A.: Wear of silicon surfaces in MEMS. Wear 271(7–8), 1050–1058 (2011)CrossRefGoogle Scholar
  17. 17.
    Ku, I.S.Y., Reddyhoff, T., Wayte, R., Choo, J.H., Holmes, A.S., Spikes, H.A.: Lubrication of microelectromechanical devices using liquids of different viscosities. J. Tribol. 134(1), 012002–012007 (2012)CrossRefGoogle Scholar
  18. 18.
    Reddyhoff, T., Ku, I., Holmes, A., Spikes, H.: Friction modifier behaviour in lubricated MEMS devices. Tribol. Lett. 41(1), 239–246 (2011)CrossRefGoogle Scholar
  19. 19.
    Keren, D., Ramanathan, G.P., Mehregany, M.: Micromotor dynamics in lubricating fluids. J. Micromech. Microeng. 4(4), 266 (1994)CrossRefGoogle Scholar
  20. 20.
    Mehregany, M., Dhuler, V.R.: Operation of electrostatic micromotors in liquid environments. J. Micromech. Microeng. 2(1), 1 (1992)CrossRefGoogle Scholar
  21. 21.
    Spikes, H.A.: The half-wetted bearing. Part 1: extended Reynolds equation. Proc. Inst. Mech. Eng. J. Eng. Tribol. 217(1), 1–14 (2003)CrossRefGoogle Scholar
  22. 22.
    Spikes, H.A.: The half-wetted bearing. Part 2: potential application in low load contacts. Proc. Inst. Mech. Eng. J. Eng. Tribol. 217(1), 15–26 (2003)CrossRefGoogle Scholar
  23. 23.
    Choo, J.H., Glovnea, R.P., Forrest, A.K., Spikes, H.A.: A low friction bearing based on liquid slip at the wall. J. Tribol. 129(3), 611–620 (2007)CrossRefGoogle Scholar
  24. 24.
    Choo, J.-H., Forrest, A., Spikes, H.: Influence of organic friction modifier on liquid slip: a new mechanism of organic friction modifier action. Tribol. Lett. 27(2), 239–244 (2007)CrossRefGoogle Scholar
  25. 25.
    Pit, R., Hervet, H., Léger, L.: Direct experimental evidence of slip in hexadecane: solid interfaces. Phys. Rev. Lett. 85(5), 980–983 (2000)CrossRefGoogle Scholar
  26. 26.
    Zhu, Y., Granick, S.: Rate-dependent slip of newtonian liquid at smooth surfaces. Phys. Rev. Lett. 87(9), 096105 (2001)CrossRefGoogle Scholar
  27. 27.
    Venier, C.G., Casserly, E.W.: Multiply-alkylated cyclopentanes (MACs): a new class of synthesized hydrocarbon fluids. Lubr. Eng. 47(7), 586–591 (1991)Google Scholar
  28. 28.
    Peterangelo, S.C., Gschwender, L., Snyder, C.E., Jones, W.R., Nguyen, Q., Jansen, M.J.: Improved additives for multiply alkylated cyclopentane-based lubricants. J. Synth. Lubr. 25(1), 31–41 (2008)CrossRefGoogle Scholar
  29. 29.
    Dube, M.J., Bollea, D., Jones, W.R., Marchetti, M., Jansen, M.J.: A new synthetic hydrocarbon liquid lubricant for space applications. Tribol. Lett. 15(1), 3–8 (2003)CrossRefGoogle Scholar
  30. 30.
    Ku, I.S.Y., Reddyhoff, T., Choo, J.H., Holmes, A.S., Spikes, H.A.: A novel tribometer for the measurement of friction in MEMS. Tribol. Int. 43(5–6), 1087–1090 (2010)CrossRefGoogle Scholar
  31. 31.
    Smeeth, M., Spikes, H., Gunsel, S.: Boundary film formation by viscosity index improvers. Tribol. Trans. 39(3), 726–734 (1996)CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media New York 2012

Authors and Affiliations

  • J. Y. Leong
    • 1
    • 2
  • T. Reddyhoff
    • 1
  • S. K. Sinha
    • 2
  • A. S. Holmes
    • 3
  • H. A. Spikes
    • 1
  1. 1.Tribology Group, Department of Mechanical EngineeringImperial College LondonLondonUK
  2. 2.Materials Group, Department of Mechanical EngineeringNational University of SingaporeSingaporeSingapore
  3. 3.Optical and Semiconductor Devices Group, Department of Electrical and Electronic EngineeringImperial College LondonLondonUK

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