Figure 3. Dynamics of contraction is set by shortest axis.

(a) Experimentally measured long axis X(t) and short axis Y(t) for filled rectangles with different initial axis ratio α_init, with constant areas X_initY_init=10,000 μm², together with Supplementary Equation 3 (solid lines), where K=X_fin/X_init=Y_fin/Y_init and τ_X and τ_Y had been determined from the fits. While K is quasi-constant due to identical stimulation density, the τ's depend on axis ratio (Supplementary Fig. 3). For each dimension L, the maximum velocity occurs at the compression time τ_L that simultaneously determines the long-time relaxation behaviour (Supplementary Equation 15). The contraction along the long axis X(t) exhibits a strong delay compared with the contraction of the short axis Y(t). The maximal contraction speed occurs much earlier in Y(t) as shown in Supplementary Fig. 3. (b) Characteristics of asymmetric contraction of initially asymmetric geometries: α_fin=X_fin/Y_fin (red squares) and α_max (blue circles) both as a function of α_init=X_init/Y_init, shown together with results of our minimal dynamic model (Supplementary Notes 3). Inset: The ratio of velocities immediately after stimulation of the perpendicular interfaces is independent of the geometry. Because the velocities vanish at equilibrium, a limiting ratio of unity signals that there is a unique acceleration and unique force strength normal to initially flat interfaces, as explained in Supplementary Notes 3. (c) Ratio of the maximal velocities obeys the relation with γ=0.4. (d) For rectangles of constant half-length X_init=400 μm and variable width, (diamonds) depends basically linearly on Y_init as expected for the undisturbed contraction, whereas (squares) gets increased nonlinearly with Y_init, indicating a hampered contraction along the long side. Using the  μm min⁻¹ value we read off for the square case. Supplementary Equation 20 of our minimal dynamic model predicts (red line) and (blue line) with γ=0.4, in agreement with these data. All network results shown here are identically stimulated with n=20 cycles.