Advertisement

Friction

pp 1–10 | Cite as

Molecular behaviors in thin film lubrication—Part two: Direct observation of the molecular orientation near the solid surface

  • Ming Gao
  • Haoyu Li
  • Liran MaEmail author
  • Yuan Gao
  • Linwei Ma
  • Jianbin LuoEmail author
Open Access
Research Article
  • 48 Downloads

Abstract

Over the past twenty years, thin film lubrication (TFL) theory has been used to characterize the molecular behaviors in lubrication films thinner than 100 nm, effectively bridging the gap between elastohydrodynamic lubrication and boundary lubrication. Unfortunately, to date, the TFL molecular model proposed in 1996 has not been directly proven by experimental detection. Herein, a method based on surface-enhanced Raman spectroscopy was developed to show both the packing and orienting of liquid molecules in the TFL regime. By trapping liquid crystal molecules between a structured silver surface and a glass surface, molecular ordering states dominated by shear effect and surface effect were successfully distinguished. A nanosandwich structure consisting of an adsorbed layer, an ordered-molecule layer, and a fluid layer was demonstrated. Molecule imaging in TFL was achieved. Our results illustrate the molecular behaviors and lubrication mechanism in nanoconfined films and facilitate the lubrication design of nanoelectromechanical and microelectromechanical systems.

Keywords

thin film lubrication molecular behaviors nematic liquid crystal surface-enhanced Raman spectroscopy lubrication theory nanosandwich structure 

Notes

Acknowledgements

The work was financially supported by the National Natural Science Foundation of China (51305225, 51527901).

Ming GAO, Liran MA, and Jianbin LUO conceived and designed the study. Ming GAO performed the main experiments and Linwei MA fabricated the SERS substrate. Ming GAO, Haoyu LI, Liran MA, and Yuan GAO wrote the manuscript. Ming GAO, Liran MA, and Jianbin LUO reviewed and edited the manuscript. All the authors read and approved the manuscript.

References

  1. [1]
    Raviv U, Klein J. Fluidity of bound hydration layers. Science 297(5586): 1540–1543 (2002)CrossRefGoogle Scholar
  2. [2]
    Raviv U, Laurat P, Klein J. Fluidity of water confined to subnanometre films. Nature 413(6851): 51–54 (2001)CrossRefGoogle Scholar
  3. [3]
    Klein J, Kumacheva E. Confinement-induced phase transitions in simple liquids. Science 269(5225): 816–819 (1995)CrossRefGoogle Scholar
  4. [4]
    Gao J P, Luedtke W D, Landman U. Nano-elastohydrodynamics: Structure, dynamics, and flow in nonuniform lubricated junctions. Science 270(5236): 605–608 (1995)CrossRefGoogle Scholar
  5. [5]
    Granick S. Motions and relaxations of confined liquids. Science 253(5026): 1374–1379 (1991)CrossRefGoogle Scholar
  6. [6]
    Israelachvili J, Gourdon D. Putting liquids under molecular scale confinement. Science 292(5518): 867–868 (2001)CrossRefGoogle Scholar
  7. [7]
    Gao X L, Dai K, Wang Z, Wang T T, He J B. Establishing quantitative structure tribo-ability relationship model using Bayesian regularization neural network. Friction 4(2): 105–115 (2016)CrossRefGoogle Scholar
  8. [8]
    Berman D, Deshmukh S A, Sankaranarayanan S K, Erdemir A, Sumant A V. Macroscale superlubricity enabled by graphene nanoscroll formation. Science 348(6239): 1118–1122 (2015)CrossRefGoogle Scholar
  9. [9]
    Thompson P A, Robbins M O. Origin of stick-slip motion in boundary lubrication. Science 250(4982): 792–794 (1990)CrossRefGoogle Scholar
  10. [10]
    Ma L R, Zhang C H, Luo J B. Investigation of the film formation mechanism of oil-in-water (O/W) emulsions. Soft Matter 7(9): 4207–4213 (2011)CrossRefGoogle Scholar
  11. [11]
    Xie G X, Luo J B, Liu S H, Guo D, Zhang C H. “Freezing” of nanoconfined fluids under an electric field. Langmuir 26(3): 1445–1448 (2010)CrossRefGoogle Scholar
  12. [12]
    Hardy W B, Doubleday I. Boundary lubrication. - The paraffin series. Proc Roy Soc A Math Phys Eng Sci 100(707): 550–574 (1922)CrossRefGoogle Scholar
  13. [13]
    Hardy W B, Doubleday I. Boundary lubrication. - The latent period and mixtures of two lubricants. Proc Roy Soc A Math Phys Eng Sci 104(724): 25–38 (1923)CrossRefGoogle Scholar
  14. [14]
    Stanton T E. Friction. London (UK): Longmans, Green and Company, 1923.Google Scholar
  15. [15]
    Bowden F P, Tabor D. The friction and lubrication of solids. Oxford (UK): Oxford University Press, 2001.zbMATHGoogle Scholar
  16. [16]
    Bailey A I, Courtney-Pratt J. The area of real contact and the shear strength of monomolecular layers of a boundary lubricant. Proc Roy Soc A Math Phys Eng Sci 227(1171): 500–515 (1955)Google Scholar
  17. [17]
    Spikes H A. Boundary lubrication and boundary Films. In Tribology Series. Dowson D, Taylor C M, Childs T H C, Godet M, Dalmaz G, Eds. Oxford: Elsevier, 1993: 331–346.Google Scholar
  18. [18]
    Georges J M, Millot S, Loubet J L, Tonck A. Drainage of thin liquid films between relatively smooth surfaces. J Chem Phys 98(9): 7345–7360 (1993)CrossRefGoogle Scholar
  19. [19]
    Johnston G J, Wayte R, Spikes H A. The measurement and study of very thin lubricant films in concentrated contacts. Tribol Tran 34(2): 187–194 (1991)CrossRefGoogle Scholar
  20. [20]
    Spikes H A. Direct observation of boundary layers. Langmuir 12(19): 4567–4573 (1996)MathSciNetCrossRefGoogle Scholar
  21. [21]
    Chinas-Castillo F. The behaviour of colloids in lubricated contacts. Master’s thesis. London (UK): University of London, 2000.Google Scholar
  22. [22]
    Ratoi M, Spikes H A, Bovington C. Langmuir-blodgett films in high-pressure rolling contacts. Tribol Trans 46(1): 24–30 (2003)CrossRefGoogle Scholar
  23. [23]
    Luo J B, Wen S Z, Huang P. Thin film lubrication. Part I. Study on the transition between EHL and thin film lubrication using a relative optical interference intensity technique. Wear 194(1–2): 107–115 (1996)CrossRefGoogle Scholar
  24. [24]
    Urbakh M, Klafter J, Gourdon D, Israelachvili J. The nonlinear nature of friction. Nature 430(6999): 525–528 (2004)CrossRefGoogle Scholar
  25. [25]
    Luo J B, Shen M W, Wen S Z. Tribological properties of nanoliquid film under an external electric field. J Appl Phys 96(11): 6733–6738 (2004)CrossRefGoogle Scholar
  26. [26]
    Shen M W, Luo J B, Wen S Z, Yao J B. Nano-tribological properties and mechanisms of the liquid crystal as an additive. Chin Sci Bull 46(14): 1227–1232 (2001)CrossRefGoogle Scholar
  27. [27]
    Luo J B, Shen M W, Shi B, Wen S Z. Thin film lubrication and lubrication map. Chin J Mech Eng 36(7): 5–10 (2000)CrossRefGoogle Scholar
  28. [28]
    Hu Y Z, Granick S. Microscopic study of thin film lubrication and its contributions to macroscopic tribology. Tribol Lett 5: 81–88 (1998)CrossRefGoogle Scholar
  29. [29]
    Zhang S H, Qiao Y J, Liu Y H, Ma L R, Luo J B. Molecular behaviors in thin film lubrication — Part one: film formation for different polarities of molecules, Friction, accepted.Google Scholar
  30. [30]
    Zhou Q, Liu Y J, He Y P, Zhang Z J, Zhao Y P. The effect of underlayer thin films on the surface-enhanced Raman scattering response of Ag nanorod substrates. Appl Phys Lett 97(12): 121902 (2010)CrossRefGoogle Scholar
  31. [31]
    Lagerwall J P F, Scalia G. A new era for liquid crystal research: applications of liquid crystals in soft matter nano-, bio-and microtechnology. Curr Appl Phys 12(6): 1387–1412 (2012)CrossRefGoogle Scholar
  32. [32]
    Woltman S J, Jay G D, Crawford G P. Liquid-crystal materials find a new order in biomedical applications. Nat Mater 6(12): 929–938 (2007)CrossRefGoogle Scholar
  33. [33]
    Ruths M, Steinberg S, Israelachvili J N. Effects of confinement and shear on the properties of thin films of thermotropic liquid crystal. Langmuir 12(26): 6637–6650 (1996)CrossRefGoogle Scholar
  34. [34]
    Cann P M, Aderin M, Johnston G J, Spikes H A. Paper V (iii) An investigation into the orientation of lubricant molecules in EHD contacts. Tribol Ser 21: 209–218 (1992)CrossRefGoogle Scholar
  35. [35]
    Nakano K. Scaling law on molecular orientation and effective viscosity of liquid-crystalline boundary films. Tribol Lett 14(1): 17–24 (2003)CrossRefGoogle Scholar
  36. [36]
    Gibbons W M, Shannon P J, Sun S T, Swetlin B J. Surface mediated alignment of nematic liquid crystals with polarized laser light. Nature 351(6321): 49–50 (1991)CrossRefGoogle Scholar
  37. [37]
    Körner H, Shiota A, Bunning T J, Ober C K. Orientation on-demand thin films: Curing of liquid crystalline networks in ac electric fields. Science 272(5259): 252–255 (1996)CrossRefGoogle Scholar
  38. [38]
    Kundu S, Lee M H, Lee S H, Kang S W. In situ homeotropic alignment of nematic liquid crystals based on photoiso merization of Azo-Dye, physical adsorption of aggregates, and consequent topographical modification. Adv Mater 25(24): 3365–3370 (2013)CrossRefGoogle Scholar
  39. [39]
    Ma L W, Huang Y, Hou M J, Li J H, Xie Z, Zhang Z J. Pinhole-containing, subnanometer-thick Al2O3 shell-coated Ag nanorods as practical substrates for quantitative surface enhanced Raman scattering. J Phys Chem C 120(1): 606–615 (2016)CrossRefGoogle Scholar
  40. [40]
    Ma L W, Wu H, Huang Y, Zou S M, Li J H, Zhang Z J. High-performance real-time SERS detection with recyclable ag nanorods@ HfO2 substrates. ACS Appl Mater Interfaces 8(40): 27162–27168 (2016)CrossRefGoogle Scholar
  41. [41]
    Ma L R, Zhang C H. Discussion on the technique of relative optical interference intensity for the measurement of lubricant film thickness. Tribol Lett 36: 239–245 (2009)CrossRefGoogle Scholar
  42. [42]
    Dowson D, Hopkins D W, Higginson G R. Elasto hydrodynamic lubrication: International series on materials science and technology. Amsterdam (UK): Elsevier, 2014.Google Scholar
  43. [43]
    Zhang S H, Liu Y H, Luo J B. In situ observation of the molecular ordering in the lubricating point contact area. J Appl Phys 116(1): 014302 (2014)CrossRefGoogle Scholar
  44. [44]
    Gähwiller C. Temperature dependence of flow alignment in nematic liquid crystals. Phys Rev Lett 28(24): 1554–1556 (1972)CrossRefGoogle Scholar
  45. [45]
    Stockman M I. Spasers explained. Nat Photon 2(6): 327–329 (2008)CrossRefGoogle Scholar
  46. [46]
    Barnes W L, Dereux A, Ebbesen T W. Surface plasmon subwavelength optics. Nature 424(6950): 824–830 (2003)CrossRefGoogle Scholar
  47. [47]
    Hao E C, Schatz G C. Electromagnetic fields around silver nanoparticles and dimers. J Chem Phys 120(1): 357–366 (2004)CrossRefGoogle Scholar
  48. [48]
    Perrot M, De Zen J M, Rothschild W G. Mid-and low frequency Raman spectra of stable and metastable crystalline states of the 4-n-alkyl-4’-cyanobiphenyl (n = 9, 11, 12) liquid crystals. J Raman Spectrosc 23(11): 633–636 (1992)CrossRefGoogle Scholar
  49. [49]
    Gray G W, Mosley A. The raman spectra of 4-Cyano-4’- pentylbiphenyl and 4-Cyano-44’-pentyl-d11-biphenyl. Mol Cryst Liq Crys 35(1–2): 71–81 (1976)CrossRefGoogle Scholar
  50. [50]
    Ge X Y, Halmans T, Li J J, Luo J B. Molecular behaviors in thin film lubrication — Part three: Superlubricity attained by polar and nonpolar molecules. Friction, DOI 10.1007/s40544-018-0254-2.Google Scholar

Copyright information

© The Author(s) 2019

Open Access: This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made.

The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder.

To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

Authors and Affiliations

  1. 1.State Key Laboratory of TribologyTsinghua UniversityBeijingChina
  2. 2.School of Metallurgy EngineeringXi’an University of Architecture and TechnologyXi’anChina
  3. 3.School of Materials Science and EngineeringTsinghua UniversityBeijingChina

Personalised recommendations