活性流体のカオスを制御する(Controlling the chaos of active fluids)

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2024-05-22 カリフォルニア大学サンタバーバラ校(UCSB)

カリフォルニア大学サンタバーバラ校(UCSB)、ミシガン大学(UM)、シカゴ大学(UChicago)の研究者たちは、アクティブ流体の自己持続的な混沌流を制御するためにトポロジカル欠陥を利用する設計ルールを開発しました。この理論モデルは、自己駆動流体を調整可能なフローで設計する道を開きます。研究チームは、特定の欠陥パターンを作成し、それらを動かし、絡める方法を示しました。欠陥は、アクティブな液晶の中で自己推進する小さなエンジンのように振る舞い、流体全体を攪拌します。この手法は、光応答性のモータープロテインとフィラメントを用いることで実験的に実現可能です。研究は、将来的に生物学的プロセスからソフトロボティクス、流体ベースのロジックデバイスにまで広がる可能性があります。

<関連情報>

能動的なトポロジカル欠陥を制御するためのデザインルール Design rules for controlling active topological defects

Suraj Shankar, Luca V. D. Scharrer, Mark J. Bowick, and M. Cristina Marchetti
Proceedings of the National Academy of Sciences  Published:May 15, 2024
DOI:https://doi.org/10.1073/pnas.2400933121

活性流体のカオスを制御する(Controlling the chaos of active fluids)

Significance

Active fluids, such as bacterial suspensions and flowing tissues, often exhibit orientational order disrupted by topological defects. Much is understood about how internal driving powers nonequilibrium dynamics, but how can we design protocols to transport and organize patterns in active fluids for functional goals? We develop an additive symmetry-based framework to control the dynamics of such topological defects by spatiotemporally manipulating active stresses. Our framework identifies design principles for controlling defect trajectories using active tweezers, as well as collections of interacting defects using patterns of activity. By combining simulations with theory, we uncover necessary symmetry conditions and trade-offs that govern defect control policies in active media, suggesting general rules for manipulating a broad range of synthetic and biological active matter.

Abstract

Topological defects play a central role in the physics of many materials, including magnets, superconductors, and liquid crystals. In active fluids, defects become autonomous particles that spontaneously propel from internal active stresses and drive chaotic flows stirring the fluid. The intimate connection between defect textures and active flow suggests that properties of active materials can be engineered by controlling defects, but design principles for their spatiotemporal control remain elusive. Here, we propose a symmetry-based additive strategy for using elementary activity patterns, as active topological tweezers, to create, move, and braid such defects. By combining theory and simulations, we demonstrate how, at the collective level, spatial activity gradients act like electric fields which, when strong enough, induce an inverted topological polarization of defects, akin to a negative susceptibility dielectric. We harness this feature in a dynamic setting to collectively pattern and transport interacting active defects. Our work establishes an additive framework to sculpt flows and manipulate active defects in both space and time, paving the way to design programmable active and living materials for transport, memory, and logic.

1700応用理学一般
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