We study the lubrication of fluid-immersed soft interfaces and show thatelastic deformation couples tangential and normal forces and thus generateslift. We consider materials that deform easily, due to either geometry (e.g. ashell) or constitutive properties (e.g. a gel or a rubber), so that the effectsof pressure and temperature on the fluid properties may be neglected. Fourdifferent system geometries are considered: a rigid cylinder moving parallel toa soft layer coating a rigid substrate; a soft cylinder moving parallel to arigid substrate; a cylindrical shell moving parallel to a rigid substrate; andfinally a cylindrical conforming journal bearing coated with a thin soft layer.In addition, for the particular case of a soft layer coating a rigid substratewe consider both elastic and poroelastic material responses. For all thesecases we find the same generic behavior: there is an optimal combination ofgeometric and material parameters that maximizes the dimensionless normal forceas a function of the softness parameter = hydrodynamic pressure/elasticstiffness = surface deflection/gap thickness which characterizes thefluid-induced deformation of the interface. The corresponding cases for aspherical slider are treated using scaling concepts.
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