Emergent hydrodynamic bound states between magnetically powered micropropellers

Martínez‐Pedrero, Fernando; Navarro-Argemí, Eloy; Ortiz-Ambriz, Antonio; Pagonabarraga, Ignacio; Tierno, Pietro

doi:10.1126/sciadv.aap9379

Cited by 64 publications

(59 citation statements)

References 51 publications

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“…To facilitate the numerical analysis of the magnetic forces between the LRMs, we can regard them as point magnet dipoles. [ 30,31,42,43 ] Therefore, the magnetic force F i,j and interaction energy

{boldnormal \hat{U}}_{i, j}

between any two LRMs (marked as LRM i and LRM j ) can be evaluated as follows:

{boldF}_{i, j} = \frac{3 μ_{0}}{4 π r_{i, j}^{5}} ([], (m_{i} \cdot {boldr}_{i, j}) m_{j} + (m_{j} \cdot {boldr}_{i, j}) m_{i} + (m_{i} \cdot m_{j}) r_{i, j} - 5 \frac{(m_{i} \cdot {boldr}_{i, j}) (m_{j} \cdot {boldr}_{i, j})}{r_{i, j}^{2}} r_{i, j})

{boldnormal \hat{U}}_{i, j} = \frac{μ_{0}}{4 π} ([], \frac{m_{i} \cdot m_{j}}{r_{i, j}^{3}} - 3 \frac{(m_{i} \cdot {boldr}_{i, j}) (m_{j} \cdot {boldr}_{i, j})}{r_{i, j}^{5}})

…”

Section: Resultsmentioning

confidence: 99%

Ferrofluid Droplets as Liquid Microrobots with Multiple Deformabilities

Fan

Sun

et al. 2020

Adv Funct Materials

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Developing microrobots with multiple deformabilities has become extremely challenging due to the lack of materials that are soft enough at the microscale level and the inability to be reconfigured after fabrication. In this study, it is aimed to prove that liquid microrobots composed of ferrofluid droplets are inherently deformable and they can be controlled, individually or in aggregate, with multiple programmable deformabilities. For example, the liquid‐microrobot monomer (LRM) can pass through narrow channels via elongation and achieve scaling via splitting and coalescence. LRMs can also reassemble into various kinds of functional liquid‐robot aggregates, such as microsticks, micropies, microtrains, microkayaks, and microrollingpins. Thus, they can respond to multi‐terrain surfaces or perform various complex tasks. Moreover, the authors' physics‐based theoretical model demonstrates dynamic self‐assembly and group behavior of a multiple LRM system, which is conducive to investigating the mechanisms behind it. These ferrofluid droplet robots provide novel solutions for some potential applications, such as untethered micromanipulation and targeted cargo delivery.

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{boldnormal \hat{U}}_{i, j}

between any two LRMs (marked as LRM i and LRM j ) can be evaluated as follows:

{boldF}_{i, j} = \frac{3 μ_{0}}{4 π r_{i, j}^{5}} ([], (m_{i} \cdot {boldr}_{i, j}) m_{j} + (m_{j} \cdot {boldr}_{i, j}) m_{i} + (m_{i} \cdot m_{j}) r_{i, j} - 5 \frac{(m_{i} \cdot {boldr}_{i, j}) (m_{j} \cdot {boldr}_{i, j})}{r_{i, j}^{2}} r_{i, j})

{boldnormal \hat{U}}_{i, j} = \frac{μ_{0}}{4 π} ([], \frac{m_{i} \cdot m_{j}}{r_{i, j}^{3}} - 3 \frac{(m_{i} \cdot {boldr}_{i, j}) (m_{j} \cdot {boldr}_{i, j})}{r_{i, j}^{5}})

…”

Section: Resultsmentioning

confidence: 99%

Ferrofluid Droplets as Liquid Microrobots with Multiple Deformabilities

Fan

Sun

et al. 2020

Adv Funct Materials

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“…Unravelling the dependence of phoretic and chemotactic effects on the surface profiles of catalyst concentration and solute-colloid interaction [8,[36][37][38] and symmetry-based classifications of pair interactions [39] have opened up the possibility of engineering active colloids with desired behaviour [40,41]. We also note that time-periodic behaviours arising through the momentum-like role of the polar orientation [19,[42][43][44] have been observed in thermophoretic colloids in a diverging source of light [45] as well as in paramecium with multiple flagellated protrusions [46].…”

Section: Introductionmentioning

confidence: 84%

“…As active particles function under a sustained energy input within an ambient medium, their effective pair interactions are in general non-reciprocal and can systematically draw both linear and angular momentum from their surroundings. The roles of hydrodynamic flow [18][19][20][21][22][23][24], diffused solute [25][26][27][28][29], local phase change [30] and optical shadowing [31,32] as mediators of these interactions have been studied, as well as guidance by nearby boundaries [33][34][35]. Unravelling the dependence of phoretic and chemotactic effects on the surface profiles of catalyst concentration and solute-colloid interaction [8,[36][37][38] and symmetry-based classifications of pair interactions [39] have opened up the possibility of engineering active colloids with desired behaviour [40,41].…”

Section: Introductionmentioning

confidence: 99%

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Pairing, waltzing and scattering of chemotactic active colloids

2019

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We study theoretically an active colloid whose polar axis of self-propulsion rotates to point parallel (antiparallel) to an imposed chemical gradient. We show that the coupling of this 'chemotactic' ('antichemotactic') response to phoretic translational motion yields remarkable two-particle dynamics reflecting the non-central and non-reciprocal character of the interaction. A pair of mutually chemotactic colloids trap each other in a final state of fixed separation resulting in a selfpropelled active dimer. A second type of bound state is observed when the polar axes undergo periodic cycles leading to phase-locked circular motion around a common centre. A pair of swimmers with mismatched phoretic mobilities execute a dance in which they twirl around one another while moving jointly in a wide circle. For sufficiently small initial separation, the speed of self-propulsion controls the transition from bound to scattering states. Mutually anti-chemotactic swimmers always scatter apart. For the special case in which one of the two colloids has uniform surface activity we succeed in exactly classifying the fixed points underlying the bound states, and identify the bifurcations leading to transitions from one type of bound state to another. The varied dynamical behaviours are accessible by tuning the swimmer design and are summarised in state diagrams.

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“…Second, there is a broad variety by now for magnetic dipolar swimmers self-assembled to active molecules. These can be chains of propellers or rotators [79,80] as [83]) and trimers (image from Ref. [8]) and heteronuclear trimers (image from Ref.…”

mentioning

confidence: 99%

Active colloidal molecules

Löwen¹

2018

EPL

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Like ordinary molecules are composed of atoms, colloidal molecules consist of several species of colloidal particles tightly bound together. If one of these components is self-propelled or swimming, novel "active colloidal molecules" emerge. Active colloidal molecules exist on various levels such as "homonuclear", "heteronuclear" and "polymeric" and possess a dynamical function moving as propellers, spinners or rotors. Self-assembly of such active complexes has been studied a lot recently and this perspective article summarizes recent progress and gives an outlook to future developments in the rapidly expanding field of active colloidal molecules. EPL perspective article invited by G. Muga

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Emergent hydrodynamic bound states between magnetically powered micropropellers

Abstract: Propelling microparticles in viscous fluid form long-living bound states maintained by hydrodynamic interactions.

Cited by 64 publications

References 51 publications

Ferrofluid Droplets as Liquid Microrobots with Multiple Deformabilities

Ferrofluid Droplets as Liquid Microrobots with Multiple Deformabilities

Pairing, waltzing and scattering of chemotactic active colloids

Active colloidal molecules

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