Optimizing an undulating magnetic microswimmer for cargo towing

Gutman, E. E.; Or, Yizhar

doi:10.1103/physreve.93.063105

Cited by 24 publications

(39 citation statements)

References 26 publications

(13 reference statements)

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“…like three-link flagella [22][23][24] , three-sphere swimmers 25 , squirmers 26 , necklace-like propellers 27 and undulating magnetic systems 28 . However, to date Lighthill's efficiency has been only experimentally estimated in few biological systems 29,30 , where the complex flagellar dynamics precludes the possibility to directly determine the relevant degrees of freedom of the microswimmer, and indirect methods such as optical tweezers, are used.…”

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confidence: 99%

“…In this formulation, the propulsion speed is controlled by three dimensionless parameters, the ratio between the particles sizes δ = R/L, α ind = µ 0 m n /(R 3 B x ) that compares the magnetic field induced by the ferromagnet on the paramagnetic particle with the external field, and the susceptibility χ of the paramagnetic particle. The propeller dynamics can be solved perturbatively 24,28,34 for a weak oscillating transverse field, B y /B x ≡ ε 1.…”

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confidence: 99%

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Direct measurement of Lighthill's energetic efficiency of a minimal magnetic microswimmer

et al. 2019

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The realization of artificial microscopic swimmers able to propel in viscous fluids is an emergent research field of fundamental interest and vast technological applications. For certain functionalities, the efficiency of the microswimmer in converting the input power provided through an external actuation into propulsive power output can be critical. Here we use a microswimmer composed by a self-assembled ferromagnetic rod and a paramagnetic sphere and directly determine its swimming efficiency when it is actuated by a swinging magnetic field. Using fast video recording and numerical simulations we fully characterize the dynamics of the propeller and identify the two independent degrees of freedom which allow its propulsion. We then obtain experimentally the Lighthill's energetic efficiency of the swimmer by measuring the power consumed during propulsion and the energy required to translate the propeller at the same speed. Finally, we discuss how the efficiency of our microswimmer could be increased upon suitable tuning of the different experimental parameters.The realization of faster and smaller micro/nanopropellers is an active topic with direct applications in the emerging fields of drug delivery 1-3 , microsurgery 4,5 and lab-on-a-chip technol-† Electronic Supplementary Information (ESI) available: Two experimental videos (.WMF) showing the dynamics of the nanorod-colloid micropropeller played at different speed. See DOI: 00.0000/00000000. ‡These authors contributed equally to this work.Although other measures of the efficiency have been proposed 19,21 , especially to account for collective ciliary motions, the Lighthill energetic efficiency remains the standard measure to account for swimming efficiency of single propellers at the microscale. This parameter has been employed in different theoretical works to analyze the performance of simple artificial designs J o u r n a l N a me , [ y e a r ] , [ v o l . ] , 1-6 | 1 arXiv:1910.00855v1 [cond-mat.soft]

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confidence: 99%

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confidence: 99%

Direct measurement of Lighthill's energetic efficiency of a minimal magnetic microswimmer

et al. 2019

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“…While the ferromagnetic microsphere oscillates, the nanotube linker acts as a torsion spring, both pulling the nonmagnetic microsphere and coupling it to the external magnetic field [12]. The external toque applied by the magnetic field and the role of the DNA as a spring break the symmetry that disallows net motion in Purcell's scallop theorem (see video) [13], [22]. In Purcell's scallop theorem, it is assumed that a two-link microswimmer has a pin joint and internal actuation only, and it is thus only capable of producing reciprocal motion that is not compatible with net locomotion [11].…”

Section: Y = Amentioning

confidence: 99%

A Customizable DNA and Microsphere-Based, Magnetically Actuated Microswimmer

Harmatz

Travers

Taylor

2020

J. Microelectromech. Syst.

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Locomoting microscale robots-microswimmershave the potential to impact numerous applications due to their ability to selectively interact with their environment with microscale control. Previous microswimmer designs lack either submicron-level precision over their construction or instantaneous control over their shape. Thus, existing microswimmer designs limit the control afforded over microswimmer interactions with their environment. This work presents a magnetically actuated microswimmer constructed from DNA and microspheres in a hybrid top-down and bottom-up assembly technique that allows for submicron-level precision over microswimmer body construction. Microscale features were fabricated via two-photon polymerization, from which polydimethylsiloxane templates were molded. Templated assembly by selective removal was used to deposit microspheres of select size and composition into the templates. This technique was confirmed to be sizeselective within a population of microspheres. To construct the microswimmer, a ferromagnetic microsphere and a nonmagnetic microsphere were deposited into a template, connected with DNA nanotubes in their arrangement, magnetized, and pulled from the template. We demonstrate instantaneous control over shape changes via expansion and contraction of a microswimmer's body in an external magnetic field. In a rotating magnetic field of constant magnitude, the microswimmer expanded as the two microspheres separated a distance of 4.1±0.5 micrometers, approximately the distance between microspheres deposited in the template. In an oscillating magnetic field, the same microswimmer contracted and locomoted 58.8±0.7 micrometers over 126 seconds.

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“…Dipolar attraction between the two magnetic particles keeps the tip of the rod on the surface of the paramagnetic sphere, a point which is identified as a virtual joint. The dynamical equations for the virtual joint in the overdamped regime are given by 51 f r + f s = 0…”

Section: Analytical Perturbative Solutionmentioning

confidence: 99%