Abstract : In order to test the fluctuation-dissipation relation on rheological properties of soft materials, we built an experiment to measure thermally excited strain in a sample and compare it to the classical response to an external stress. The rheometer is based on a cylindrical Couette geometry. We use differential interferometry to achieve better than 10(-10) rad/rootHz sensitivity in angular position above 0.5 Hz. The forcing method, based on electrostatic interaction in a capacitor, generates torques comparable to that of thermal noise. Experiments on a calibrated silicon oil show good agreement between response and fluctuation measurements.
Ludovic Bellon, Lionel Buisson, Sergio Ciliberto, Franck Vittoz. Zero applied stress rheometer. Review of Scientific Instruments, American Institute of Physics, 2002, pp.3286-3290. ⟨10.1063/1.1499210⟩. ⟨ensl-00179779⟩
