Fig. 3.

Mechanical model of the interface and tissue response. (A) Deflection of the interface in a pull-and-release (trap on–trap off) experiment. The model (blue line) accurately fits the experimental data (black). (Inset) The simplest analogous viscoelastic model is a Maxwell arm in parallel with a spring. For a trap stiffness, $k_t$ = 50 pN⋅μm⁻¹, and fit parameters values are $k_1$ = 15 pN⋅μm⁻¹, $k_2$ = 55 pN⋅μm⁻¹, $\zeta$ = 1.5 × 10⁻⁴ m⋅Pa⋅s, and $C_{\eta }$ = 1.5 × 10⁻⁵ m⋅Pa⋅s. Note that this value of $C_{\eta }$ is consistent with our previous estimate (2 ± 1 × 10⁻⁵ m⋅Pa⋅s). The same parameter values are used in the simulations. (B) Deflection perpendicular to the interfaces is tracked over time along lines perpendicular to cell interfaces (red), which allows measurement of deformation away from the targeted interface (yellow arrowhead). (Scale bar: 10 µm.) (C) Kymograph of interface deflections in the (Left) experimental and (Right) simulated tissues. Only the interfaces adjacent to the target interface display significant deflection. (D) Deflection of the target (black) and neighbor (at one- and two-cells distance; magenta and green, respectively) interfaces in the (Left) experimental and (Right) simulated tissues. (E) In the model, the movement of a vertex results from a balance between tension from adjacent bonds and viscous friction. (F) Overlay of the undeformed (purple) and deformed (green) tissue in the (Left) experimental and (Right) simulated tissue. (G) Spatial decay of interface deflections over the neighboring cells. Comparison between experiments and simulations.