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Hydrodynamic Forces : from Boundary Slippage to the Mechanics of Soft Surfaces
Surface forces measurements have been an invaluable tool to perform quantitative mechanical probing at a nano-scale, and have contributed to our understanding of the friction of liquids onto solid surfaces and dissipation in confined liquid layers. But beyond the scope of friction, the measurement of nano-hydrodynamic forces has reached a precision allowing one to use them as a probe for the mechanics of soft surfaces. The direct mechanical testing of small and soft objects is indeed an open problem of the nano-scale world. As surface effects become larger than volume effects, the use of contact or indentation methods to measure the elastic properties of soft systems such as thin polymer films or biologic tissues, raises ambiguities. In this talk I will show how nano-hydrodynamics can be used to measure the elasticity of nano-bubbles, or the visco-elastic moduli of thin elastomer films, opening the way toward non-contact and non-intrusive measurements of elastic properties of small and soft objects.