The low-T limit, on the other hand, characterized by T * /ε' ≃ const, can be attributed to the formation of kinetic traps (Figure ). While random collisions can lead to misbinding between two blocks, these mistakes can be corrected by thermal fluctuations, provided that ε' is sufficiently small 47 . However, when T is too low or ε'/ε too close to one, for undesired bonds to be corrected, partial reversibility of bonds is hindered and results in kinetically-trapped structures. This phenomenon is clearly demonstrated in the MD simulations: incorrect bonds formed during the assembly can be "healed" when T ≳ T * and/or ε'/ε ≲ ε' * /ε , whereas assembly outside these conditions results in kinetic-traps, structures with multiple incorrect bonds (Figure and). This suggests that the low-T limit arises because the entropic gain, TΔs, for a chain of N blocks fragmenting into two shorter pieces is balanced by the increase in bond energy, Δu = ε'. The change in free energy is thus Δf = Δu * -T * Δs = 0, thereby T * /ε' * ~ 1/Δs. As this entropy change should be relatively insensitive to small changes in concentration, size, and target structure shape, we observed a nearly constant T * /ε' * for all our simulated structures of slightly varying N, ⍴, and shapes (Figure , Table ).