Ultrasound-activated ciliary bands for microrobotic systems inspired by starfish

Cornel Dillinger,Nitesh Nama,Daniel Ahmed

doi:10.1038/s41467-021-26607-y

Cornel Dillinger, Nitesh Nama + Show 1 more

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https://doi.org/10.1038/s41467-021-26607-y

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Journal: Nature Communications	Publication Date: Nov 9, 2021
Citations: 74	License type: open-access

Affiliation: ETH Zurich, University of Nebraska–Lincoln

Abstract

Cilia are short, hair-like appendages ubiquitous in various biological systems, which have evolved to manipulate and gather food in liquids at regimes where viscosity dominates inertia. Inspired by these natural systems, synthetic cilia have been developed and utilized in microfluidics and microrobotics to achieve functionalities such as propulsion, liquid pumping and mixing, and particle manipulation. Here, we demonstrate ultrasound-activated synthetic ciliary bands that mimic the natural arrangements of ciliary bands on the surface of starfish larva. Our system leverages nonlinear acoustics at microscales to drive bulk fluid motion via acoustically actuated small-amplitude oscillations of synthetic cilia. By arranging the planar ciliary bands angled towards (+) or away (−) from each other, we achieve bulk fluid motion akin to a flow source or sink. We further combine these flow characteristics with a physical principle to circumvent the scallop theorem and realize acoustic-based propulsion at microscales. Finally, inspired by the feeding mechanism of a starfish larva, we demonstrate an analogous microparticle trap by arranging + and − ciliary bands adjacent to each other.

Highlights

Cilia are short, hair-like appendages ubiquitous in various biological systems, which have evolved to manipulate and gather food in liquids at regimes where viscosity dominates inertia
Synthetic cilia promise solutions for many fundamental functions including propulsion, liquid pumping and mixing, and particle manipulation—all difficult to realize at microscale due to the lack of inertia
While the acoustic vibration of individual synthetic cilia has been employed for liquid pumping[13], the interaction of multiple cilia in close proximity, i.e., in ciliary bands, remains largely unexplored

Summary

Introduction

Hair-like appendages ubiquitous in various biological systems, which have evolved to manipulate and gather food in liquids at regimes where viscosity dominates inertia Inspired by these natural systems, synthetic cilia have been developed and utilized in microfluidics and microrobotics to achieve functionalities such as propulsion, liquid pumping and mixing, and particle manipulation. 1234567890():,; Cilia are short, hair-like appendages present in numerous biological living systems They can be found on the surfaces of many organisms, including algae and invertebrate larvae, which are naturally evolved to manipulate and gather food in liquids, where viscosity dominates inertia. Nature’s swimmers provide ready inspiration; for example, marine invertebrate larvae, such as those of Patiria miniate (starfish), can adjust the orientation of cilia in their ciliary bands (i.e., densely packed cilia) to control the direction of liquid flow, developing an analogous fluid source and sink and exploiting them for propulsion and feeding[11]. By arranging + and − ciliary bands adjacent to each other, we engineer a novel microparticle transport and trapping mechanism that mimics the feeding mechanism of starfish larva

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