Metachronal Actuation of Microscale Magnetic Artificial Cilia

Abstract

Biological cells often interact with the environment through carpets of microscopic hair-like cilia. These elastic structures are known to beat in a synchronized wavy fashion called metachronal motion to produce fluid transport. Metachronal motion emerges due to a phase difference between beating cycles of neighboring cilia and appears as traveling waves propagating along the ciliary carpet. We demonstrate submerged in water microscale magnetic cilia that are externally actuated to beat in a metachronal fashion. Two approaches are used to induce coordinated phase differences among the beating cilia. In the first case, we fabricate cilia with an imposed gradient of geometrical properties that are subject to a rotating uniform magnetic field. In the second scenario, a ciliary array is composed of identical cilia that experience a magnetic field that varies spatiotemporally. We demonstrate that magnetic cilia can achieve symplectic, antiplectic, and leoplectic metachrony.

Metachronal μ-Cilia for On-Chip Integrated Pumps and Climbing Robots

“… 25 This has shifted the focus of researchers from the design and fabrication of synchronous cilia to metachronal cilia. The mechanism of creating metachronal cilia can be summarized into two categories: (i) applying different forces to each cilium within an array of cilia 23 , 26 , 27 and (ii) designing an array of cilia with different responses to a uniformly applied stimulus such as a uniform magnetic field. 19 , 27 − 30 The latter is beneficial due to its much simpler actuation method.…”

“…The mechanism of creating metachronal cilia can be summarized into two categories: (i) applying different forces to each cilium within an array of cilia 23 , 26 , 27 and (ii) designing an array of cilia with different responses to a uniformly applied stimulus such as a uniform magnetic field. 19 , 27 − 30 The latter is beneficial due to its much simpler actuation method. The fabrication approaches presented in previous papers, however, are either time-consuming because complex assembly steps are needed 28 , 29 or they are based on expensive raw materials, costly processes, or complex actuation devices.…”

“…The fabrication approaches presented in previous papers, however, are either time-consuming because complex assembly steps are needed 28 , 29 or they are based on expensive raw materials, costly processes, or complex actuation devices. 19 , 27 , 28 , 30 Moreover, the relatively large size of the reported metachronal cilia, typically several millimeters or larger, 19 , 28 − 30 render them difficult to be integrated in common microfluidic devices. Two of these previous publications demonstrated fluid flow induced by the metachronal artificial cilia.…”

Amphibious Transport of Fluids and Solids by Soft Magnetic Carpets

“…The efficiency of the ciliated fluid transport has motivated scientists to mimic this strategy, primarily to replicate the biological functionality. [ 30 , 31 , 32 , 33 , 34 , 35 ] Additionally, biomimetic cilia can be driven by external fields with relative ease. [ 30 , 31 , 32 , 36 , 37 ] A recent demonstration thereof includes solid cargo transport employing electric fields in a liquid environment (silicone oil).…”

A theory of magneto-elastic nanorods obtained through rigorous dimension reduction

“…These functionalities are particularly appealing when the overall dimensions of the actuators are at the millimeter scale, or even smaller, since at those scales, magnetic fields can be specified not only in magnitude, but also in direction and spatial gradients, enlarging the class of achievable shapes [27]. Over the past decades, many applications have been proposed to exploit MREs as gripping tools [40], manipulators [39], micro-swimmers [24,5] or in biomimetic applications [19,21].…”