Improving the Lubrication of Silicon Surfaces Using Ionic Liquids as Oil Additives: The Effect of Sulfur-Based Functional Groups


The performance of micro/nanoelectromechanical systems (MEMS/NEMS) relies on efficient lubrication. In the present work, new sulfur-based organic salts were tested as additives in a polyethylene glycol to lubricate silicon surfaces used in the manufacture of MEMS/NEMS. Seven salts were tested: 1-butylsulfonic-3-methylimidazolium triflate [(C4SO3H)MIM][TfO], thiamine triflate [Thiamine][TfO]2, 1-ethyl-3-methylimidazolium camphorsulfonate [C2MIM][CSA] [isomers (R) and (S)], 1,3-dimethylpiridinium methylsulfate [C1-3pic][MeSO4], methylimidazolium methanesulfonate [HMIM][MeSO3], and tetramethylguanidine methanesulfonate [TMG][MeSO3]. A nanotribometer was used to determine the friction coefficients using steel spheres as counter bodies. Excellent tribological properties were achieved with the additives containing the anions [MeSO4] and [MeSO3]. The films formed on the Si substrates were studied by FTIR, ellipsometry and AFM. A mixed lubrication mechanism was proposed where additive adsorption avoids contact between sliding surfaces.

Graphical Abstract

Sulfur-based organic salts as additives in the base oil PEG200 significantly improve the lubrication of silicon surfaces used in MEMS/NEMS

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This research was funded by the projects UID/QUI/00100/2019, UID/QUI/50006/2019, UIDB/00100/2020, UID/NAN/50024/2013, PEst-C/LA0006/2013, and UID/EMS/50022/2019 (LAETA). L. C. Branco and M. C. Donato thank to financial support of FCT/MCTES through grants IF/0041/2013/CP1161/CT00 and SFRH/BD/140079/2018, respectively.

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Antunes, M., Donato, M.T., Paz, V. et al. Improving the Lubrication of Silicon Surfaces Using Ionic Liquids as Oil Additives: The Effect of Sulfur-Based Functional Groups. Tribol Lett 68, 70 (2020).

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  • Ionic liquids
  • Additives
  • Silicon
  • Friction coefficient