Geometric control of active matter

The ability of chemically or optically powered active matter to self-organise and spontaneously flow makes these systems increasingly attractive in smart microfluidics and materials design. Active matter has the potential to serve as the bedrock of customisable, controllable transport and processing systems, but to fully harness this potential, its intrinsic tendency toward turbulence must be tamed. Geometric confinement has recently emerged as an excellent stabilising scheme, allowing complex yet controllable behaviours to be engineered by careful design of the flow environment. First, we will take a tour through recent experimental and theoretical studies showcasing the power of geometry over active matter, including a recent realisation of a bacterial Ising model. I will then introduce a new model for active flow in complex network-like environments, where network topology is the key driver of self-organising behaviour. This will culminate in the theory of active matter logic, proposing how carefully designed flow topologies could be harnessed to construct logic gates and to store data, thus laying the foundation for autonomous microfluidic logic devices driven by bacterial fluids, active liquid crystals or chemically engineered motile colloids.