Microrheology using a custom-made AFM*

In the past few years, a new method was developed to measure local properties of liquids (X. Xiong \textit{et al.}, Phys. Rev. E 80, 2009). This method consists of gluing a micron-sized glass fiber at the tip of an AFM cantilever and probing the liquid with it. In ENS Lyon, this method was perfected (C. Devailly \textit{et al.}, EPL, 106 5, 2014) with the help of an interferometer developped in the same laboratory (L. Bellon \textit{et al.}, Opt. Commun. 207 49, 2002 and P. Paolino \textit{et al.}, Rev. Sci. Instrum. 84, 2013), which background noise can reach $ 10^{-14}\ m/\sqrt{Hz} $. This method allows us to measure a wide range of viscosities ($ 1\ mPa.s$ to $ 500\ mPa.s $) of transparent and opaque fluids using a small sample volume ($ \sim 5\ mL $). In this presentation, I will briefly describe the interferometer developped in ENS Lyon, then explain precisely the microrheology measurements and then compare the experimental results to a model developped by M. Benzaquen.