Programming active-molecule dynamics via intramolecular nonreciprocity

TL;DR

This paper introduces intramolecular nonreciprocity as a minimal mechanism to program and control active-molecule and collective active matter dynamics, enabling diverse behaviors without redesigning particles.

Contribution

It demonstrates how internal nonreciprocal coupling in active molecules allows for programmable single-molecule and collective behaviors, expanding the design space of active matter systems.

Findings

Heterogeneous sequences produce unique trajectories not seen in homogeneous sequences.

Modifying internal sequences shifts the MIPS onset significantly without changing interactions.

Intramolecular nonreciprocity enables sequence-level control of active-matter dynamics.

Abstract

The dynamics of a self-propelled particle are typically hard-wired by its microscopic construction, limiting the range of behaviors accessible without redesigning the particle itself. Here we show that intramolecular nonreciprocity provides a minimal and versatile mechanism to overcome this constraint. We construct active molecules from short chains of two species of self-propelled particles whose propulsion directions are coupled nonreciprocally according to a prescribed internal sequence. At the single-molecule level, homogeneous sequences exhibit standard persistent random-walk dynamics, whereas heterogeneous sequences produce distinct trajectories inaccessible to either constituent species alone. At the collective level, using motility-induced phase separation (MIPS) as a representative example, we find that modifying the internal sequence shifts the MIPS onset by multiple orders of magnitude in propulsion strength, without altering particle-level interactions. These results demonstrate that intramolecular nonreciprocity among a small set of active components enables sequence-level programmability from single-molecule dynamics to emergent collective behavior, providing a minimal mechanism to encode and control active-matter dynamics across scales.