Metachronal Motion across Scales: Current Challenges and Future Directions

Abstract

Metachronal motion is used across a wide range of organisms for a diverse set of functions. However, despite its ubiquity, analysis of this behavior has been difficult to generalize across systems. Here we provide an overview of known commonalities and differences between systems that use metachrony to generate fluid flow. We also discuss strategies for standardizing terminology and defining future investigative directions that are analogous to other established subfields of biomechanics. Lastly, we outline key challenges that are common to many metachronal systems, opportunities that have arisen due to the advent of new technology (both experimental and computational), and next steps for community development and collaboration across the nascent network of metachronal researchers.

Natural Cilia and Pine Needles Combinedly Inspired Asymmetric Pillar Actuators for All-Space Liquid Transport and Self-Regulated Robotic Locomotion

“…Through the metachronal motion that occurs widely and across scales in organisms, another important function of our artificial cilia systems is to serve as a bioinspired crawling robot. ,, However, a problem with these crawling robots is that they lack a rotating degree of freedom and thus cannot perform the self-rotatable motion. Considering the advantage of our AI-MPA in intelligently switching 2D/3D beating-based metachronal motion, we demonstrate that the AI-MPA can realize the controllable crawling motion and self-rotatable motions with a convenient magnetic control method (i.e., the translational motion of the magnetic).…”

“…Switchable Robotic Crawling and Self-Rotatable Motion. Through the metachronal motion that occurs widely and across scales in organisms, 54 another important function of our artificial cilia systems is to serve as a bioinspired crawling robot. 28,29,37 However, a problem with these crawling robots is that they lack a rotating degree of freedom and thus cannot perform the self-rotatable motion.…”

RoboKrill : a metachronal drag-based swimmer robot

“…During the return stroke, the profile area decreases, reducing the drag on the appendages, such that the net force on each appendage acts in the swimming direction, creating a net thrust force sufficient to overcome the drag on the body [30,38]. Although there is not yet a unifying theory of fluid dynamics and force distribution for drag-based metachronal swimming, studies have shown that it is more effective than lift-based propulsion for accelerating, braking, and turning at low speeds as it can generate significant thrust over short periods, making this propulsion mechanism more adequate for maneuvering at intermediate Re [6,[41][42][43].…”

Self-sustained three-dimensional beating of a model eukaryotic flagellum

“…1,2 The mechanisms governing the beating of cilia and flagella, as well as the underlying routes to their synchronization, have been a topic of considerable interest. [3][4][5][6] The core of an eukaryotic flagellum or cilium (below we consider flagella only) is the axoneme, a cylindrical skeleton structure consisting of nine microtubule doublets on the circumference and a pair of single microtubules at the center -the ''9 + 2'' structure; [7][8][9] see Fig. 1.…”

“…1,2 The mechanisms governing the beating of cilia and flagella, as well as the underlying routes to their synchronization, have been a topic of considerable interest. 3–6…”