  Living systems are capable of locomotion, reconfiguration, and replication.
To perform these tasks, cells spatiotemporally coordinate the interactions of
force-generating, "active" molecules that create and manipulate non-equilibrium
structures and force fields that span up to millimeter length scales [1-3].
Experimental active matter systems of biological or synthetic molecules are
capable of spontaneously organizing into structures [4,5] and generating global
flows [6-9]. However, these experimental systems lack the spatiotemporal
control found in cells, limiting their utility for studying non-equilibrium
phenomena and bioinspired engineering. Here, we uncover non-equilibrium
phenomena and principles by optically controlling structures and fluid flow in
an engineered system of active biomolecules. Our engineered system consists of
purified microtubules and light-activatable motor proteins that crosslink and
organize microtubules into distinct structures upon illumination. We develop
basic operations, defined as sets of light patterns, to create, move, and merge
microtubule structures. By composing these basic operations, we are able to
create microtubule networks that span several hundred microns in length and
contract at speeds up to an order of magnitude faster than the speed of an
individual motor. We manipulate these contractile networks to generate and
sculpt persistent fluid flows. The principles of boundary-mediated control we
uncover may be used to study emergent cellular structures and forces and to
develop programmable active matter devices.
