Title: 

Nonreciprocal dynamics of active structures

Abstract:

Reciprocity is a general property of many linear physical systems, encoding a symmetry relation between two processes in which, for instance, input and output are interchanged. While this property underpins several theoretical and experimental tools, its constraints limit or impede behaviors such as net propulsion at low Reynolds numbers and asymmetric wave propagation in elastic media. Breaking reciprocity offers rich mathematical challenges and opportunities for novel functional materials.

In this seminar, I will report on the mathematical modelling and experimental realization of reciprocity breaking in soft active structures. Active matter can negate reciprocity by converting stored or ambient energy into mechanical work, thus disrupting the symmetries underlying classical reciprocity theorems. 

Using polyelectrolyte hydrogel filaments as prototypical one-dimensional active structures, we show that flutter instability can be harnessed as a new mechanism for undulatory locomotion and periodic beating of active filaments with minimal actuation. This instability, often viewed as detrimental, here instead emerges as a form of embodied mechanical intelligence, reducing control complexity. Beyond instabilities, the intrinsic responsiveness of polyelectrolyte hydrogels to environmental stimuli breaks spatial symmetry at the material level. We explore this phenomenology in a periodic metabeam composed of active rods, demonstrating nonreciprocal transmission in both static and dynamic regimes. The material’s ability to harvest energy from external stimuli compensates viscous dissipation, enabling near-lossless unidirectional wave propagation in a fluid environment.

Speaker:

Dr. Ariel Boiardi, Postdoctoral Scholar, Mechanics and Materials Unit (Fried Unit), OIST

Zoom:

URL: https://oist.zoom.us/j/91562741452?pwd=8DwfKRM4LlKmBxMsCuyQENBX9OOAse.1
ID: 915 6274 1452
Passcord: 909281