A new tuning fork-based instrument for oscillatory shear rheology of nano-confined liquids

We present a new method to measure rheological response of liquids confined to nano-scale which exhibit a considerable slow-down in dynamics compared to bulk liquids. The method relies on using a robust force sensor that has a sensitivity to measure shear forces in the range of 1 to 10 nN and a stiffness of 55000 N/m to avoid thermal noise. Off-resonance operation ensures application of a range of shear frequencies . This range is higher than the inverse of the system's mechanical relaxation time and allows the measurement of non-linear effects emerging due to significant "slow down" in dynamics upon confinement. The instrument is a step forward towards resolving the controversies about the nature of nano-confined liquids.