The Influence of Mechanical Deformations on Surface Force Measurements

Romain Lhermerout (1)

1 LIPhy - Laboratoire Interdisciplinaire de Physique [Saint Martin d’Hères]

Surface Force Balance (SFB) experiments have been performed in dry atmosphere and 1 across an ionic liquid, combining the analysis of the surface interactions and deformations, and 2 illustrate that the mechanical deformations of the surfaces have important consequences for the 3 force measurements. First, we find that the variation of the contact radius with the force across 4 the ionic liquid is well described only by the Derjaguin-Muller-Toporov (DMT) model, in contrast 5 with the usual consideration that SFB experiments are always in the Johnson-Kendall-Roberts 6 (JKR) regime. Secondly, we observe that mica does not only bend but can also experiences a 7 compression, of order 1 nm with 7 µm mica. We present a modified procedure to calibrate the mica 8 thickness in dry atmosphere, and we show that the structural forces measured across the ionic 9 liquid cannot be described by the usual exponentially decaying harmonic oscillation, but should 10 be considered as a convolution of the surface forces across the liquid and the mechanical response 11 of the confining solids. The measured structural force profile is fitted with a heuristic formulation 12 supposing that mica compression is dominant over liquid compression, and a scaling criterion is 13 proposed to distinguish situations where the solid deformation is negligible or dominant.

Mots clés: surface force balance; contact mechanics; surface interactions

Domaines: Dynamique des Fluides [physics.flu-dyn]; Matière Molle [cond-mat.soft]

Romain Lhermerout. The Influence of Mechanical Deformations on Surface Force Measurements. Lubricants, 2021, 9 (7), pp.69. ⟨10.3390/lubricants9070069⟩. ⟨hal-03830712v2⟩