Fig. 3.

Mechanical-power output and efficiency predicted from the 1D model. (A) When the external force works against cell migration, we can take the minus of ${\mathcal{I}}_{\mathrm{e}\mathrm{x}\mathrm{t}}=f_{\mathrm{e}\mathrm{x}\mathrm{t}}^{\mathrm{f}}{v}_0$ as a power output. (B and C) Power–velocity relation. Within each line, $f_{\mathrm{e}\mathrm{x}\mathrm{t}}^{\mathrm{f}}$ increases from right to left. In B, darker lines represent higher rates of actin polymerization. ${\eta }_{\mathrm{s}\mathrm{t}}=10^4$ Pa$\cdot$s/$\mathrm{\mu }{\mathrm{m}}^2$. In C, darker lines represent higher rates of active solute pumping. $d_g=10^6$ Pa$\cdot$s/$\mathrm{\mu }$m. (D–F) Contours of the mechanical-output efficiency of migration defined by $\gamma ={\left(-{\mathcal{I}}_{\mathrm{e}\mathrm{x}\mathrm{t}}\right)}_{max}/{\mathcal{I}}_{\mathrm{c}\mathrm{e}\mathrm{l}\mathrm{l}}$. (D) Output efficiency of actin-driven cell migration ${\gamma }_{\mathrm{a}\mathrm{c}\mathrm{t}\mathrm{i}\mathrm{n}}$. (E) Output efficiency of water-driven cell migration ${\gamma }_{\mathrm{w}\mathrm{a}\mathrm{t}\mathrm{e}\mathrm{r}}$. (F) The difference of efficiency of the 2 mechanisms of migrations, ${\gamma }_{\mathrm{a}\mathrm{c}\mathrm{t}\mathrm{i}\mathrm{n}}-{\gamma }_{\mathrm{w}\mathrm{a}\mathrm{t}\mathrm{e}\mathrm{r}}$. The white line is the cross-over line showing ${\gamma }_{\mathrm{a}\mathrm{c}\mathrm{t}\mathrm{i}\mathrm{n}}-{\gamma }_{\mathrm{w}\mathrm{a}\mathrm{t}\mathrm{e}\mathrm{r}}=0$.