“…Active tile assembly models include the activatable tile model where tiles pass signals to each other and can change their internal 'state' based on other tiles that join to the assembly [53,54,37]. This interesting generalization of the tile assembly model is essentially an asynchronous nondeterministic cellular automaton of a certain kind, and may indeed be implementable using DNA origami tiles with strand displacement signals [53,54]. There are also models of algorithmic self-assembly where after a structure grows, tiles can be removed, such as the kinetic tile-assembly model [77,78,17] (which implements the chemical kinetics of tile assembly) and the negative-strength glue model [25,59,56], or the RNAse enzyme model [1,57,21].…”