In the above analysis, the kink angle possesses no direct dependence on flaw size. For a channel crack in a thin film, the critical pressure for fracture possesses no flaw length dependence, so long as the flaw is substantially longer than the film thickness. This greatly simplifies analysis of the plan-view cells outlined here. For a conventional cell format, an indirect dependence on flaw size occurs via the dependence of 𝑃𝑃 on the flaw size. In applying this analysis to conventional cells, we must assume a representative flaw size and stress intensity factor for failure to estimate a representative 𝑃𝑃. As discussed in the main text, we use 𝑎𝑎 = 10μm and 𝐾𝐾 𝑐𝑐 = 1 MPa ⋅ √m. We note that for flaws initially smaller than the representative 10 μm used here, the initial value of 𝑃𝑃 is higher. However, with propagation, the value of 𝑃𝑃 decreases until reaching that of the representative flaw discussed here. Thus, the analysis outlined herein should still apply.