Positional anchoring of smectic liquid crystals

Positional anchoring of the smectic-A(SA) liquid crystal 40.8 at a glass plate interface is measured with a micromechanical technique: stress oscillations at layer thickness scale are observed under shear normal to the layers. Similar oscillations are observed on its smectic-B phase, and previously in plastic crystals. These oscillations are explained by shear-induced surface melting and recrystallization. The corresponding SA positional anchoring energy is ∼${10}^{\mathrm{-}8}$–${10}^{\mathrm{-}9}$ J/${\mathrm{m}}^2$. This unidimensional periodic melting is a model for solid friction in soft matter.