Squeeze Film Force Modeling with Considering Slip and Inertia Effects Between Hydrophobic Surfaces Within Submillimeter Clearance

Squeeze film force exists but is undesirable in some engineering applications such as immersion lithography and micro-electro mechanical systems. The dynamic characteristics of such systems can be improved by adopting hydrophobic surfaces. In addition to squeeze film damping effects, slip effects are prominent and the inertial effects can be neglected with small film thickness, while inertial effects are prominent and slip effects can be neglected with large film thickness. Existing squeeze film force models that ignore inertia effects will cause unacceptable deviations between hydrophobic surfaces with clearance from dozens to hundreds of microns. In this paper, the squeeze film force model is formulated based on Navier–Stokes equations and two parameters slip boundary conditions while simultaneously considering slip and inertia effects. Experiments using different squeeze film thicknesses and squeeze amplitudes are conducted with parallelism between two specimen surfaces of less than 0.01°. The experimental results show that the slip and inertia effects are critical for accurately predicting the squeeze film force between hydrophobic surfaces under moderate film thickness. The predicted errors of the proposed model can be significantly reduced to less than 0.5% after proper fitting of the two slip parameters under all the test conditions. The method can be adopted for the identification of slip parameters and derivation of kinetic models for systems with squeeze film.