Complex pathways and memory in compressed corrugated sheets

The nonlinear response of driven complex materials—disordered magnets, amorphous media, and crumpled sheets—features intricate transition pathways where the system repeatedly hops between metastable states. Such pathways encode memory effects and may allow information processing, yet tools are lacking to experimentally observe and control these pathways, and their full breadth has not been explored. Here we introduce compression of corrugated elastic sheets to precisely observe and manipulate their full, multistep pathways, which are reproducible, robust, and controlled by geometry. We show how manipulation of the boundaries allows us to elicit multiple targeted pathways from a single sample. In all cases, each state in the pathway can be encoded by the binary state of material bits called hysterons, and the strength of their interactions plays a crucial role. In particular, as function of increasing interaction strength, we observe Preisach pathways, expected in systems of independently switching hysterons; scrambled pathways that evidence hitherto unexplored interactions between these material bits; and accumulator pathways which leverage these interactions to perform an elementary computation. Our work opens a route to probe, manipulate, and understand complex pathways, impacting future applications in soft robotics and information processing in materials.

Modeling epithelial tissues as active-elastic sheets reproduce contraction pulses and predict rip resistance

Confluent epithelial tissues can be viewed as soft active solids, as their individual cells contract in response to local conditions. Little is known about the emergent properties of such materials. Empirical observations have shown contraction waves propagation in various epithelia, yet the governing mechanism, as well as its physiological function, is still unclear. Here we propose an experiment-inspired model for such dynamic epithelia. We show how the widespread cellular response of contraction-under-tension is sufficient to give rise to propagating contraction pulses, by mapping numerically and theoretically the consequences of such a cellular response. The model explains observed phenomena but also predicts enhanced rip-resistance as an emergent property of such cellular sheets. Unlike healing post-rupture, these sheets avoid it by actively re-distributing external stresses across their surface. The mechanism is relevant to a broad class of tissues, especially such under challenging mechanical conditions, and may inspire engineering of synthetic materials.

Coil–stretch-like transition of elastic sheets in extensional flows

A thin soft sheet suspended in a fluid undergoing planar or biaxial flow displays a hysteretic transition between compact and stretched states as the flow strength changes. This transition is analogous to the “coil–stretch transition” observed for long linear polymers in these flows.