Stochastic self-assembly is a hot topic in chemistry and biology. The general idea is that if you pour building blocks into a recipient and stir, your blocks will eventually react with one another to form new structures. Such self-assembly reactions can be regulated to make sure there is always a desired amount of assembled structures in the mix (tunable reaction network). This can be seen as analogous to the use of enzymes to regulate metabolic reactions in the body.

To understand how such reactions work, Napp et al. built a robotic testbed that can emulate stochastic self-assembly. Their amazing setup presented in the self-explanatory video below uses an air hockey table on which robots float around randomly. There are two types of building blocks in the system, that can self-assemble to form two-piece structures (dimers). A robot is then added to the system to regulate the reaction by splitting assembled structures apart. This robot uses energy each time it disassembles a structure, and needs some time to recharge thanks to solar panels before it can break any new structures. Conveniently, by tuning the speed at which these robots recharge it is possible to modulate the speed at which structures are broken and therefore regulate the amount of assembled structures present in the system over time!

In the future, such systems could be imagined to build a large variety of complex structures, including self-assembling miniature robots.