Geometric constraints and optimization in externally driven propulsion

Mirzae, Yoni; Dubrovski, Oles; Kenneth, Oded; Morozov, Konstantin I.; Leshansky, Alexander

doi:10.1126/scirobotics.aas8713

Cited by 39 publications

(43 citation statements)

References 23 publications

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“…This was later corroborated in experiments with planar microswimmers [20]. Furthermore, the swimming properties of the achiral microswimmers were extensively investigated, with the conclusion that achiral planar shapes are nearly optimal propellers [21]. Similar achiral structures with asymmetric arms have also been used to obtain imbalanced forces and induced torques in other systems [22,23].…”

Section: Introductionmentioning

confidence: 78%

µ-PIV Measurements of Flows Generated by Photolithography-Fabricated Achiral Microswimmers

et al. 2019

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Robotic micro/nanoswimmers can potentially be used as tools for medical applications, such as drug delivery and noninvasive surgery. Recently, achiral microswimmers have gained significant attention because of their simple structures, which enables high-throughput fabrication and size scalability. Here, microparticle image velocimetry (µ-PIV) was used to study the hydrodynamics of achiral microswimmers near a boundary. The structures of these microswimmers resemble the letter L and were fabricated using photolithography and thin-film deposition. Through µ-PIV measurements, the velocity flow fields of the microswimmers rotating at different frequencies were observed. The results herein yield an understanding of the hydrodynamics of the L-shaped microswimmers, which will be useful in applications such as fluidic manipulation.

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Section: Introductionmentioning

confidence: 78%

µ-PIV Measurements of Flows Generated by Photolithography-Fabricated Achiral Microswimmers

et al. 2019

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“…The in-sync propulsion (27) persists in a limited range of actuation frequencies, ω * < ω < ω s-o . Considering a solution corresponding to an acute precession angle θ and noting that the solution of the rotational problem assuming cylindrical anisotropy does not depend on α, we find that ω * and ω s-o are given to the first approximation by the respective expressions (18) and (19) at ε = 0, such that…”

Section: Magnetization In E1e2-plane Approximate Solutionmentioning

confidence: 99%

Unidirectional Propulsion of Planar Magnetic Nanomachines

et al. 2019

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Steering of magnetic nano-/microhelices by a rotating magnetic field is considered as a promising technique for controlled navigation of tiny objects through viscous fluidic environments. It has been recently demonstrated that simple geometrically achiral planar structures can also be steered efficiently. Such planar propellers are interesting for practical reasons, as they can be mass-fabricated using standard micro/nanolithography techniques. While planar magnetic structures are prone to inplane magnetization, under the effect of an in-plane rotating magnetic field, they exhibit, at most, propulsion due to spontaneous symmetry breaking, i.e., they can propel either parallel or antiparallel to the rotation axis of the field depending on their initial orientation. Here we demonstrate that actuation by a conically rotating magnetic field (i.e., superposition of in-plane rotating field and constant field orthogonal to it) can yield efficient unidirectional propulsion of planar and magnetized in-plane structures. In particular, we found that a highly symmetrical V-shape magnetized along its symmetry axis which exhibits no net propulsion in in-plane rotating field, exhibits unidirectional in-sync propulsion with a constant (frequency-independent) velocity when actuated by the conically rotating field.

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“…With the expansion of the design space of possible magnetic propellers, the computational prediction of the behavior of customized shapes becomes highly desirable, which however remains a challenging task from the theoretical point of view despite decades of study of low-Reynolds-number hydrodynamics (Elgeti et al, 2015 ; Lauga, 2016 ). Analytical solutions are only possible for simple shapes (Ghosh et al, 2012 , 2013 ; Keaveny et al, 2013 ; Man and Lauga, 2013 ; Morozov and Leshansky, 2014 ; Xu et al, 2016 ; Morozov et al, 2017 ), or for slender clusters (Morozov and Leshansky, 2014 ; Morozov et al, 2017 ; Mirzae et al, 2018 ). When analytical solutions are not possible, hydrodynamic simulations can be used to describe the propeller behavior.…”

Section: Introductionmentioning

confidence: 99%

Bead-Based Hydrodynamic Simulations of Rigid Magnetic Micropropellers

et al. 2018

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The field of synthetic microswimmers, micro-robots moving in aqueous environments, has evolved significantly in the last years. Micro-robots actuated and steered by external magnetic fields are of particular interest because of the biocompatibility of this energy source and the possibility of remote control, features suited for biomedical applications. While initial work has mostly focused on helical shapes, the design space under consideration has widened considerably with recent works, opening up new possibilities for optimization of propellers to meet specific requirements. Understanding the relation between shape on the one hand and targeted actuation and steerability on the other hand requires an understanding of their propulsion behavior. Here we propose hydrodynamic simulations for the characterization of rigid micropropellers of any shape, actuated by rotating external magnetic fields. The method consists of approximating the propellers by rigid clusters of spheres. We characterize the influence of model parameters on the swimming behavior to identify optimal simulation parameters using helical propellers as a test system. We then explore the behavior of randomly shaped propellers that were recently characterized experimentally. The simulations show that the orientation of the magnetic moment with respect to the propeller's internal coordinate system has a strong impact on the propulsion behavior and has to be known with a precision of ≤ 5° to predict the propeller's velocity-frequency curve. This result emphasizes the importance of the magnetic properties of the micropropellers for the design of desired functionalities for potential biomedical applications, and in particular the importance of their orientation within the propeller's structure.

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Geometric constraints and optimization in externally driven propulsion

Cited by 39 publications

References 23 publications

µ-PIV Measurements of Flows Generated by Photolithography-Fabricated Achiral Microswimmers

µ-PIV Measurements of Flows Generated by Photolithography-Fabricated Achiral Microswimmers

Unidirectional Propulsion of Planar Magnetic Nanomachines

Bead-Based Hydrodynamic Simulations of Rigid Magnetic Micropropellers

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