Figure 1

Experimental setup. (a) Microfluidic cross-flow geometry controlled by a pressure difference $\Delta P$ between inlet and outlet branches. (b) Close-up of the velocity field near the stagnation point, showing a typical actin filament. (c) Raw contour (red) of an actin filament and definition of geometric quantities used in the analysis.Reuse & Permissions

Figure 2

Filament modes, fluctuations, and dynamics in the extensional regime $\dot{\gamma }>0$. (a) The first four orthonormal eigenfunctions $W^{(n)}$ (solid lines) obtained from (3) for $\Sigma =0$, and $W^{(1)}$ for $\Sigma =100$ (red dashed line), illustrating the insensitivity of the fundamental bending mode shape to the tension. (b) Experimentally measured local variance as a function of position along actin filaments (symbols), and theoretical contribution from the fundamental mode (solid red line). (c) Filament-end fluctuation variance [raw data (open circles) and binned (red circles)] and scaled full relaxation time [raw data (open squares) and binned (green squares)] as a function of tension. Theoretical results are solid red and green curves, respectively.Reuse & Permissions

Figure 3

The stretch-coil transition of single actin filaments. (a)–(c) Snapshots of buckling filaments beyond the instability, $\Sigma =-0.55$ (a), $-1.9$ (b), and $-47$ (c). Scale bars are $3\mu \mathrm{m}$, indicated times since the first frame are rescaled by $\dot{\gamma }$, and $-$ ($+$) denotes a flow with compression along $x$ ($y$). The fundamental mode is seen in (a) and (b), a higher-order mode in (c) during compression along $x$ followed by $y$. (d) Fractional compression measured by the end-to-end displacement $\mathcal{L}$, as a function of $|\Sigma |$. Dashed lines indicate instability thresholds for modes whose shapes are shown. The gray band indicates the noise floor.Reuse & Permissions