Feedback control and delayed interactions in active matter

TL;DR

This paper reviews how feedback control with delays influences active matter, revealing that time delays can induce complex behaviors like pattern formation and act as control parameters for dynamical states.

Contribution

It highlights the role of time delay as an underexplored dimension in active matter, connecting intrinsic response dynamics to functional behaviors.

Findings

Delay induces activity, chirality, and transport.

Time delay can switch between dynamical states.

Experimental realizations demonstrate these effects.

Abstract

Feedback control plays a central role in active matter, yet it is inevitably accompanied by noise and finite perception--action delays. This Perspective reviews recent advances on active systems with delayed interactions, showing how time delay can induce activity, chirality, transport, and collective pattern formation, and can act as an effective control parameter for switching between dynamical states. We discuss representative single-particle and many-body systems, highlight key experimental realizations, and argue that time delay constitutes an underexplored dimension of morphological intelligence--where intrinsic response dynamics, rather than explicit sensors or computation, enable functional behavior in active matter.