Unidirectional flow from continuous broken symmetries

TL;DR

This paper demonstrates how distributed broken symmetries in systems like lymphatic vessels enable continuous, unidirectional fluid transport, with implications across biological and artificial systems.

Contribution

It extends the concept of non-reciprocal transport from condensed matter to biological and artificial fluid systems, showing how spatiotemporal excitations control flow.

Findings

Distributed leaflets act as continuous broken symmetries in lymphatic transport.

Waveshapes propagating against flow can maximize transport.

Contraction wavelength and pulsatility influence flow rate.

Abstract

Locally broken symmetries are used across fields to transport matter, particles and information in preferential directions. Beyond local mechanisms, spatially distributed nonlinearities in crystalline media have enabled non-reciprocal transport, a rectification mechanism that operates continuously across scales and frequencies. Here, we show that this concept applies beyond condensed matter, to fluid transport in living organisms and artificial systems. We take the example of the lymphatic vascular system, which transports interstitial fluid in mammals, and demonstrate that distributed leaflets act as continuous broken symmetries. We build an artificial model of a collecting lymphatic and investigate the naturally richer dynamics of unidirectional transport that arises from spatiotemporal excitations. We observe robust and scalable transport for any waveshape and external pressure gradients. We show experimentally and theoretically that the contraction wavelength, directionality, and pulsatility control the flow rate. In particular, we counterintuitively find waveshapes that maximize transport when propagating against the direction of the flow. Overall, our findings advance the understanding of unidirectional fluid transport in living systems and beyond, and reveal how coupling nonlinearities with spatiotemporal excitations can tune such transport across fields.