Probing length scale-dependent viscoelasticity from bending fluctuations of filaments

Micron-sized beads are commonly used to perform microrheology in soft media. The size of the particles sets the length scale at which properties are probed. This can limit results when the properties of the medium vary with length scale. A typical example of such a system are living cells. Cells are constructed hierarchically, with structural elements ranging from nano- to mesoscopic scales. Here, we introduce the use of semi-flexible filaments/tubes to probe scale-dependent dynamics. We analyze shape fluctuations of semi-flexible filaments. We show that the bending dynamics of filaments can be used to probe the physical properties of such media at multiple scales, corresponding to the wavelengths of the modes analyzed.