Abstract
Being intrinsically nonequilibrium, active materials can potentially perform
functions that would be thermodynamically forbidden in passive materials.
However, active systems have diverse local attractors that correspond to
distinct dynamical states, many of which exhibit chaotic turbulent-like
dynamics and thus cannot perform work or useful functions. Designing such a
system to choose a specific dynamical state is a formidable challenge.
Motivated by recent advances enabling opto-genetic control of experimental
active materials, we describe an optimal control theory framework that
identifies a spatiotemporal sequence of light-generated activity that drives an
active nematic system toward a prescribed dynamical steady-state. Active
nematics are unstable to spontaneous defect proliferation and chaotic streaming
dynamics in the absence of control. We demonstrate that optimal control theory
can compute activity fields that redirect the dynamics into a variety of
alternative dynamical programs and functions. This includes dynamically
reconfiguring between states, and selecting and stabilizing emergent behaviors
that do not correspond to attractors, and are hence unstable in the
uncontrolled system. Our results provide a roadmap to leverage optical control
methods to rationally design structure, dynamics, and function in a wide
variety of active materials.