Cited by 390Electrostatics and Colloid InteractionsForce Microscopy Techniques and ApplicationsLubricants and Their Additives

Origins of hydration lubrication

Open access
Ma, Liran, Gaisinskaya-Kipnis, Anastasia, Kampf, Nir, Klein, Jacob·2015·Nature Communications

Abstract

Why is friction in healthy hips and knees so low? Hydration lubrication, according to which hydration shells surrounding charges act as lubricating elements in boundary layers (including those coating cartilage in joints), has been invoked to account for the extremely low sliding friction between surfaces in aqueous media, but not well understood. Here we report the direct determination of energy dissipation within such sheared hydration shells. By trapping hydrated ions in a 0.4-1 nm gap between atomically smooth charged surfaces as they slide past each other, we are able to separate the dissipation modes of the friction and, in particular, identify the viscous losses in the subnanometre hydration shells. Our results shed light on the origins of hydration lubrication, with potential implications both for aqueous boundary lubricants and for biolubrication.

Integrity signals

Registry

Crossref · 10.1038/ncomms7060

Cites

33 of 33 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

1 of 40 cited sources checked · 0 supported · 0 flagged · accuracy not yet measured

  • Premisecitation

    In all relevant studies to date, the measured friction may have been dominated by other dissipation pathways, such as polymer chains disentangling past each other or distortion of sheared liposomes.

    “This is because in all relevant studies to date, including refs 4-11, the measured friction may have been dominated by other dissipation pathways, such as polymer chains disentangling past each other 10,11 or distortion of sheared liposomes 9 .”
    Quote in the paperSubstantial claim1 of 3 sources checked
    • cites [4] Sakuma, H., Otsuki, K. & Kurihara, K. Viscosity and lubricity of aqueous NaCl solution confined between mica surfaces studied by shear resonance measurement. Phys. Rev. Lett. 96, 046101–046104 (2006). source
    • cites [9] Goldberg, R. et al. Boundary lubricants with exceptionally low friction coefficients based on 2D close-packed phosphatidylcholine liposomes. Adv. Mater. 23, 3517–3521 (2011). source
    • cites [10] Chen, M., Briscoe, W. H., Armes, S. P. & Klein, J. Lubrication at physiological pressures by polyzwitterionic brushes. Science 323, 1698–1702 (2009). source

      The Published paper section describes viscous dissipation in the interpenetration zone of sliding polymer brushes and reports that entanglement increased friction in earlier brush studies. It does not address distortion of sheared liposomes or establish that other dissipation pathways may have dominated measured friction in all relevant studies. (LLM, conf=0.85)

      Experimental — accuracy not yet measured
  • Findingown data

    From the slope qF_s/q(ln(v_s))≈0.5×10^-6 N in Fig. 4, a value for Ω≈2×10^-23 m^3 is extracted.

    “From the slope qF s /q(ln(n s ))E0.5 Â 10 À 6 N in Fig. 4, we extract a value for OE2 Â 10 À 23 m 3 .”
    Quote in the paperSubstantial claim
  • Findingown data

    In the high-load regime, the variation of shear force with sliding velocity is close to logarithmic, F_s = A + B ln(v_s), over some orders of magnitude in v_s.

    “the variation is close to logarithmic, F s ¼ A þ B.ln(n s ), where A and B are constants, over some orders of magnitude in n s .”
    Quote in the paperSubstantial claim
  • Findingown data

    In the low-load regime, the variation of shear force with sliding velocity is much closer to linear, F_s - F_s,0 = C v_s.

    “the variation is much closer to linear, F s -F s,0 ¼ C.n s , where F s,0 (Methods) and C are independent of n s .”
    Quote in the paperSubstantial claim
  • Findingcitation

    At D≈2 nm, there is characteristic repulsion arising from tightly bound hydration shells surrounding Na+ counterions trapped between negatively charged mica surfaces.

    “At Doca 2 nm, we observe the characteristic repulsion arising from the tightly bound hydration shells [14][15][16][17][18] surrounding the Na þ counterions trapped between the negatively charged mica surfaces.”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites [14] Hensen, E. J. M. & Smit, B. Why clays swell. J. Phys. Chem. B 106, 12664–12667 (2002). source
    • cites [15] Israelachvili, J. N. Intermolecular and Surface Forces 3rd edn Academic (2011). source
    • cites [16] Lane, J. M. D., Chandross, M., Stevens, M. J. & Grest, G. S. Water in nanoconfinement between hydrophilic self-assembled monolayers. Langmuir 24, 5209–5212 (2008). source
  • May combine two claims. 12
  • The quote only partly states this claim. 2
  • Classified as probably not a substantial claim. 6
  • May combine two claims.

    Findingreasoning

    The number of water molecules per Na+ ion trapped in the gap is n_w ≈ 6, comparable with the number 4-7 of water molecules in the first hydration shell of a Na+ ion.

    “The number of water molecules n w per Na þ ion trapped in the gap is then given by n w ¼ r H2O /r c/i E6, where r H2O is the number density of water molecules ¼ (density of water)/(mass of a water molecule).Thus, n w is comparable with the number, 4-7, of water molecules in the first (most tightly held) hydration shell of a Na þ ion 23,27 .”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [23] Cotton, F. A. & Wilkinson, G. Advanced Inorganic Chemistry 5th edn Wiley (1998).

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites [27] Saluja, P. P. S. Environment of ions in aqueous solutions. Int. Rev. Sci. Electrochem. Part 1 Phys. Chem. 2 6, 1–51 (1976).

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • May combine two claims.

    Findingown data

    The present study identifies the dissipation pathway and the viscous losses in the bound hydration layers alone, which are characterized by an effective viscosity orders of magnitude larger than that of non-hydration water.

    “In particular, we identify the dissipation pathway and the viscous losses in the bound hydration layers alone, which are characterized by an effective viscosity orders of magnitude larger than that of non-hydration water.”
    Quote in the paperSubstantial claim
  • The quote only partly states this claim.

    Findingown data

    The effective shear viscosity of the confined film in the low-load regime is η_eff = 0.22±0.07 Pa.s.

    “from the measured slope C of the blue band in Fig. 4, we may extract the effective viscosity of the confined film, Z eff ¼ 0.22±0.07Pa.s.”
    Quote in the paperSubstantial claim
  • Classified as probably not a substantial claim.

    Premisecitation

    Hydration lubrication has been invoked to account for the extremely low sliding friction observed at high pressures between charged surfaces in high-salt solution, or when coated by surfactants, liposomes or hydrated polymer brushes.

    “Over the past decade, the concept of hydration lubrication has been invoked to account for the extremely low sliding friction observed at high pressures between charged surfaces in high-salt solution [3][4][5] , or when coated by surfactants [6][7][8] , liposomes 9 or hydrated polymer brushes [10][11][12] boundary layers resembling those at articular cartilage surfaces 12,13 .”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites [3] Raviv, U. & Klein, J. Fluidity of bound hydration layers. Science 297, 1540–1543 (2002). source
    • cites [4] Sakuma, H., Otsuki, K. & Kurihara, K. Viscosity and lubricity of aqueous NaCl solution confined between mica surfaces studied by shear resonance measurement. Phys. Rev. Lett. 96, 046101–046104 (2006). source
    • cites [5] Donose, B. C., Vakarelski, I. U. & Higashitani, K. Silica surface lubrication by hydrated cations adsorption from electrolyte solutions. Langmuir 21, 1834–1839 (2005). source
  • May combine two claims.

    Study design and conductown data

    τΩ≈3×10^-20 J >> 4kBT, which is the assumption underlying equation 3.

    “We can check that indeed tOE3 Â 10 À 20 J4 4k B T (E4 Â 10 À 21 J), which is the assumption underlying in equation 3.”
    Quote in the paperSubstantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims. The quote only partly states this claim.

    Study design and conductown data

    Contact areas between the surfaces were evaluated using the Hertzian contact mechanics relation and compared with contact areas obtained by directly measuring the flattening of the optical fringe tips, generally within 30% of each other over all experiments.

    “Comparison of these values with contact areas obtained by directly measuring the flattening of the optical fringe tips (as in Fig. 2b in the main paper) in the high-load regime were generally within 30% of each other over all experiments.”
    Quote in the paperNot a substantial claim
  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    Hydration shells formed by water molecules are tenaciously attached to the charges they surround and cannot be easily squeezed out on compression.

    “According to this, hydration shells formed by water molecules are tenaciously attached to the charges they surround, and so cannot be easily squeezed out on compression [14][15][16][17][18]”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites [14] Hensen, E. J. M. & Smit, B. Why clays swell. J. Phys. Chem. B 106, 12664–12667 (2002). source
    • cites [15] Israelachvili, J. N. Intermolecular and Surface Forces 3rd edn Academic (2011). source
    • cites [16] Lane, J. M. D., Chandross, M., Stevens, M. J. & Grest, G. S. Water in nanoconfinement between hydrophilic self-assembled monolayers. Langmuir 24, 5209–5212 (2008). source
  • May combine two claims.

    Premisecitation

    Hydration shells are labile and respond to shear in a fluid manner.

    “yet are labile and so respond to shear in a fluid manner.”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites [14] Hensen, E. J. M. & Smit, B. Why clays swell. J. Phys. Chem. B 106, 12664–12667 (2002). source
    • cites [15] Israelachvili, J. N. Intermolecular and Surface Forces 3rd edn Academic (2011). source
    • cites [16] Lane, J. M. D., Chandross, M., Stevens, M. J. & Grest, G. S. Water in nanoconfinement between hydrophilic self-assembled monolayers. Langmuir 24, 5209–5212 (2008). source
  • May combine two claims.

    Study design and conductown data

    Shear forces vary reversibly with shear velocity and normal load, indicating that no surface damage occurs during shear.

    “We note that, within the scatter for a given contact point, the shear forces vary reversibly with the shear velocity and with normal load, indicating that no surface damage occurs during the shear (Methods).”
    Quote in the paperNot a substantial claim
  • Classified as probably not a substantial claim.

    Study design and conductreasoning

    Only experiments where both F_n(D) and F_s profiles were reversible and reproducible with respect to load and sliding velocities, and thus clearly undamaged, are reported.

    “Only experiments where both F n (D) and F s profiles were reversible and reproducible (within the scatter) with respect to load and sliding velocities, and thus clearly undamaged, are reported”
    Quote in the paperSubstantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductown data

    Results are reported from all nine independent experiments in which no damage occurred.

    “(results are reported from all nine independent experiments in which no damage occurred, that is, different pairs of mica sheets, with different contact points in each”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductcitation

    The D_h and D_l values are the mean of 23 and 25 measurements in the high-load and low-load regimes respectively, where the quoted uncertainty is twice the standard error in the mean.

    “The D h and D l values are the mean of 23 and 25 measurements in the high-load (ca 5-8 mN) and low-load (ca 0.1-0.2mN) regimes respectively, where the quoted uncertainty is twice the standard error in the mean given by Peter's formula 33 .”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [33] Squires, G. L. Practical Physics McGraw-Hill (1968). source
  • May combine two claims.

    Study design and conductcitation

    The present study traps hydrated ions in the gap between molecularly smooth surfaces and measures friction at pressures and shear rates one to two orders of magnitude higher than previously achieved.

    “The present study overcomes these limitations by trapping hydrated ions in the gap between molecularly smooth surfaces, and measuring the friction between them as they slide at pressures and shear rates one to two orders of magnitude higher than previously achieved 3 .”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [3] Raviv, U. & Klein, J. Fluidity of bound hydration layers. Science 297, 1540–1543 (2002). source
  • May combine two claims.

    Premisecitation

    The viscosity of water that is not in hydration layers but is likewise confined to subnanometre films by mica surfaces has an effective value comparable to η_H2O and so is also some two orders of magnitude smaller than η_eff.

    “We emphasize that the viscosity of water that is not in hydration layers surrounding a charge, but is likewise confined to subnanometre films by mica surfaces, has an effective value that is comparable to Z H20 (ref.29) and so is also some two orders of magnitude smaller than Z eff .”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [29] Raviv, U., Laurat, P. & Klein, J. Fluidity of water confined to sub-nanometre films. Nature 413, 51–54 (2001). source
  • May combine two claims.

    Study design and conductreasoning

    The relative offset of the opposing lattices was not controlled in the study, and the scatter in the F_s versus F_n plot is attributed to such differences between different experiments and contact points.

    “This relative offset of the opposing lattices was not controlled in our study, and we attribute the scatter in the F s versus F n plot in Fig. 2b to such differences between different experiments and contact points.”
    Quote in the paperSubstantial claim
  • May combine two claims.

    Interpretationreasoning

    In the low-load regime, D_l = 0.85±0.15 nm, the dissipation is in the sheared hydration shells themselves.

    “the behaviour in the lower-load regime, D l ¼ 0.85±0.15nm, reveals the dissipation in the sheared hydration shells themselves.”
    Quote in the paperSubstantial claim
16 of 16
  • The authors state this as an assumption.

    The exchange time of water molecules in the hydration shell of Na+ can be taken as approximately the relaxation time of water within the hydration shells.

    “The value of o H2O,Na þ E10 9 s À 1 corresponds to an exchange time t H2O,Na þ ¼ (1/o H2O,Na þ )E10 À 9 s, which may be taken as approximately the relaxation time of water within the hydration shells.”
  • The authors state this as an assumption.

    Liquid viscosity is proportional to molecular relaxation times (η=Gτ) as long as the shear rate is much lower than τ^-1.

    “On general grounds 30 , one expects liquid viscosity Z to be proportional to molecular relaxation times t, Z ¼ Gt (where G is a limiting high-frequency modulus), as long as the shear rate is much lower than t À 1 , as is the case in the present study.”
2 of 2

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • High-load separation has two stated uncertainties

    Minor

    The high-load separation is reported as 0.48 ± 0.16 nm in the Results but as 0.48 ± 0.15 nm in the Discussion. Both refer to D_h, so the stated uncertainty is inconsistent.

  • High-load logarithmic slope is attributed to the low-load figure

    Minor

    The Methods attribute the logarithmic slope used to estimate the activated volume to Fig. 4. The text identifies Fig. 4 as the low-load, approximately linear regime and places the high-load logarithmic data in Fig. 3.

2 of 2

Cites

Flagged first, then by citations

Research works printed but not linked: 3

  1. Evans, D. F. & Wennerstrom, H. The Colloidal Domain 2nd edn Wiley (1999).
  2. Saluja, P. P. S. Environment of ions in aqueous solutions. Int. Rev. Sci. Electrochem. Part 1 Phys. Chem. 2 6, 1–51 (1976).
  3. Ferry, J. D. Viscoelastic Properties of Polymers 3rd edn Wiley (1985).

Cited by

Sorted by citations

Authors
Ma, L., Gaisinskaya-Kipnis, A., Kampf, N., & Klein, J.
Affiliations
  • State Key Laboratory of Tribology (CN)
  • Weizmann Institute of Science (IL)
Corresponding author
Klein, Jacob
Venue
Nature Communications
Published
2015-01-14
Volume
6
Issue
1
Pages
6060-6060
ISSN
2041-1723 (ISSN-L)
OpenAlex
W1991834170
Cited by
390
References
30
Citations by year
2026: 30 · 2025: 47 · 2024: 66 · 2023: 36 · 2022: 50 · 2021: 33 · 2020: 37 · 2019: 32 · 2018: 17 · 2017: 18 · 2016: 14 · 2015: 9 · 2014: 1
FWCI
13.20
Type
journal article
Language
en
Open access
Locations
  • Nature Communications (publishedVersion)
  • PubMed (publishedVersion)
  • RePEc: Research Papers in Economics (submittedVersion)
Funders
  • McCutchen Foundation
  • Minerva Foundation
  • Israel Science Foundation
Topics
  • Physical Sciences › Chemistry › Physical and Theoretical Chemistry › Electrostatics and Colloid Interactions
  • Physical Sciences › Physics and Astronomy › Atomic and Molecular Physics, and Optics › Force Microscopy Techniques and Applications
  • Physical Sciences › Engineering › Mechanical Engineering › Lubricants and Their Additives
Keywords
hydration lubrication, friction, energy dissipation, hydration shell, biolubrication, hydrated ions, zwitterion, sliding friction, cartilage, joint lubrication, viscous losses, charged surfaces
MeSH terms
Joints, Lubrication, Models, Theoretical, Friction

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