Submersed micropatterned structures control active nematic flow, topology, and concentration

Thijssen, Kristian; Khaladj, Dimitrius A.; Aghvami, S. Ali; Gharbi, Mohamed Amine; Fraden, Seth; Yeomans, Julia M.; Hirst, Linda S.; Shendruk, Tyler N.

doi:10.1073/pnas.2106038118

Cited by 46 publications

(45 citation statements)

References 68 publications

(83 reference statements)

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“…Beyond substrate friction, recent work has studied the effects of a different type of external dissipation on active nematic turbulence [28,146]. Instead of on a solid substrate, active nematic microtubule films can be assembled at an oil-water interface.…”

Section: Interaction With An External Fluidmentioning

confidence: 99%

Active Turbulence

Alert¹,

Casademunt²,

Joanny³

2021

Preprint

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Active fluids exhibit spontaneous flows with complex spatiotemporal structure, which have been observed in bacterial suspensions, sperm cells, cytoskeletal suspensions, self-propelled colloids, and cell tissues. Despite occurring in the absence of inertia, chaotic active flows are reminiscent of inertial turbulence, and hence they are known as active turbulence. Here, we survey the field, providing a unified perspective over different classes of active turbulence. To this end, we divide our review in sections for systems with either polar or nematic order, and with or without momentum conservation (wet/dry). Comparing to inertial turbulence, we highlight the emergence of power-law scaling with either universal or non-universal exponents. We also contrast scenarios for the transition from steady to chaotic flows, and we discuss the absence of energy cascades. We link this feature to both the existence of intrinsic length scales and the self-organized nature of energy injection in active turbulence, which are fundamental differences with inertial turbulence. We close by outlining the emerging picture, remaining challenges, and future directions.

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Section: Interaction With An External Fluidmentioning

confidence: 99%

Active Turbulence

Alert¹,

Casademunt²,

Joanny³

2021

Preprint

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“…Surface patterning can also be realized using a smectic oil, which can provide an anisotropic environment and render the turbulent-like, active nematic flows into more ordered flows ( 23 , 24 ). More recently, a submersed micropatterned surface also demonstrates the capability of control over defect dynamics and spontaneous flows in microtubule-based active nematic film ( 54 ). We anticipate that our concept of activity patterning could be combined with these different patterning techniques and may lead to unprecedented phenomena and new applications.…”

Section: Discussionmentioning

confidence: 99%

Logic operations with active topological defects

2022

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Logic operations performed by semiconductor-based transistors are the basis of modern computing. There is considerable interest in creating autonomous materials systems endowed with the capability to make decisions. In this work, we introduce the concept of using topological defects in active matter to perform logic operations. When an extensile active stress in a nematic liquid crystal is turned on, +1/2 defects can self-propel, in analogy to electron transport under a voltage gradient. By relying on hydrodynamic simulations of active nematics, we demonstrate that patterns of activity, when combined with surfaces imparting certain orientations, can be used to control the formation and transport of +1/2 defects. We further show that asymmetric high- and low-activity patterns can be used to create effective defect gates, tunnels, and amplifiers. The proposed active systems offer the potential to perform computations and transmit information in active soft materials, including actin-, tubulin-, and cell-based systems.

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“…where we have defined the parameter z = 4(αR 2 0 γ )/(Kγ c ), which acts as a dimensionless activity number that balances the colloid size against the active nematic length scale a = K/α [54][55][56][57] and the ratio of drag coefficients γ /γ c . As such, activity introduces a radial potential whose slope depends on the angular position of the colloid.…”

Section: Colloid-defect Pair Dynamicsmentioning

confidence: 99%

Passive Janus particles are self-propelled in active nematics

Loewe

Shendruk

2022

New J. Phys.

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While active systems possess notable potential to form the foundation of new classes of autonomous materials, designing systems that can extract functional work from active surroundings has proven challenging. In this work, we extend these efforts to the realm of designed active liquid crystal/colloidal composites. We propose suspending colloidal particles with Janus anchoring conditions in an active nematic medium. These passive Janus particles become effectively self-propelled once immersed into an active nematic bath. The self-propulsion of passive Janus particles arises from the effective +1/2 topological charge their surface enforces on the surrounding active fluid. We analytically study their dynamics and the orientational dependence on the position of a companion −1/2 defect. We predict that at sufficiently small activity, the colloid and companion defect remain bound to each other, with the defect strongly orienting the colloid to propel either parallel or perpendicular to the nematic. At sufficiently high activity, we predict an unbinding of the colloid/defect pair. This work demonstrates how suspending engineered colloids in active liquid crystals may present a path to extracting activity to drive functionality.

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Submersed micropatterned structures control active nematic flow, topology, and concentration

Cited by 46 publications

References 68 publications

Active Turbulence

Active Turbulence

Logic operations with active topological defects

Passive Janus particles are self-propelled in active nematics

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