Figure 6: Cyclic hardening in actin/filamin networks.
Actin/filamin networks at ca=9.5 μM, R=0.1 at 21 °C show cyclic hardening. (a) The protocol for the control experiment (black) and the cyclic shearing procedure (blue—different strain amplitudes are indicated by different blue colors) are shown. Thick lines mark the first upward shearing to the respective maximum strain. (b) The black line shows the network response to a constant shear rate 1.4%/s. Blue colors show the response to the cyclic shearing procedure shown in (a). Thick lines show the response to the first cycle applied up to the respective maximum strain. Only the response to upward shearing is shown. At the maximal cyclically applied strain the stress decreases as a function of cycle number (c). Higher stresses are reached beyond this strain (b). (d) Confocal images (x projection of 63 μm; z projection of 130 μm—surface near regions are not shown in order to reduce the background fluorescence) which are taken during the experiment (time points where the images are taken are indicated in the protocol (a)) reveal that cyclic shearing causes unbundling. A larger number of thin bundles appears and the mesh size decreases. Scale bars denote 50 μm and are also valid for z-projections. Videos showing one image per cycle can be seen in the Supplementary Movie S3 and S4.
