Efficient shapes for microswimming: From three-body swimmers to helical flagella

Bet, Bram; Boosten, Gijs; Dijkstra, Marjolein; Roij, René van

doi:10.1063/1.4976647

Cited by 19 publications

(13 citation statements)

References 54 publications

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“…In this work, we calculate the rigid body resistance tensor of (active) bead chains using a bead-shell model 60 , 61 , in which the surface of a rigid body is homogeneously covered by a large number (M) of small spheres of radius a . When this cluster of M spheres is given a non-zero common velocity, a disturbance flow field is created, which in turn causes hydrodynamic interactions between the small spheres that are given by the Rotne-Prager mobility tensor 62 , 63 .…”

Section: Methodsmentioning

confidence: 99%

Rational design and dynamics of self-propelled colloidal bead chains: from rotators to flagella

Vutukuri

Bet

Roij

et al. 2017

Sci Rep

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The quest for designing new self-propelled colloids is fuelled by the demand for simple experimental models to study the collective behaviour of their more complex natural counterparts. Most synthetic self-propelled particles move by converting the input energy into translational motion. In this work we address the question if simple self-propelled spheres can assemble into more complex structures that exhibit rotational motion, possibly coupled with translational motion as in flagella. We exploit a combination of induced dipolar interactions and a bonding step to create permanent linear bead chains, composed of self-propelled Janus spheres, with a well-controlled internal structure. Next, we study how flexibility between individual swimmers in a chain can affect its swimming behaviour. Permanent rigid chains showed only active rotational or spinning motion, whereas longer semi-flexible chains showed both translational and rotational motion resembling flagella like-motion, in the presence of the fuel. Moreover, we are able to reproduce our experimental results using numerical calculations with a minimal model, which includes full hydrodynamic interactions with the fluid. Our method is general and opens a new way to design novel self-propelled colloids with complex swimming behaviours, using different complex starting building blocks in combination with the flexibility between them.

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Section: Methodsmentioning

confidence: 99%

Rational design and dynamics of self-propelled colloidal bead chains: from rotators to flagella

Vutukuri

Bet

Roij

et al. 2017

Sci Rep

Self Cite

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“…With this choice, we calculate a lower limit for the efficiency. Other authors [54] suggest using an average friction coefficient, corresponding to the time evolution of the swimmer shape during the stroke. We prefer to use the less dissipative configuration (the most contracted) to define the efficiency since the shape changes are consequence of the swimming stroke.…”

Section: Efficiencymentioning

confidence: 99%

Boosting micromachine studies with Stokesian Dynamics

Berdakin,

Marconi,

Banchio

2021

Preprint

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Artificial microswimmers, nano and microrobots, are essential in many applications from engineering to biology and medicine. We present a Stokesian Dynamics study of the dynamical properties and efficiency of one of the simplest artificial swimmer, the three linked spheres swimmer (TLS), extensively shown to be an excellent and model example of a deformable micromachine. Results for two different swimming strokes are compared with an approximate solution based on point force interactions. While this approximation accurately reproduces the solutions for swimmers with long arms and strokes of small amplitude, it fails when the amplitude of the stroke is such that the spheres come close together, a condition where indeed the largest efficiencies are obtained. We find that swimmers with a "square stroke cycle" result more efficient than those with "circular stroke cycle" when the swimmer arms are long compared with the sphere radius, but the differences between the two strokes are smaller when the arms of the swimmers are short. This extended theoretical research of TLS incorporates a much precise description of the swimmer hydrodynamics, demonstrating the relevance of considering the finite size of the constitutive microswimmers spheres. This work expects to trigger future innovative steps contributing to the design of micro and nanomachines and its applications.

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“…For the purpose of illustration, we show the blob function of two variables whose width is controlled by the regularization parameter f . The efficiency of the bacterial motility system has been the focus of numerous theoretical [4][5][6], computational [7][8][9][10][11][12], and experimental works [13][14][15]. For a comprehensive review, see Ref.…”

Section: Introductionmentioning

confidence: 99%

Using Experimentally Calibrated Regularized Stokeslets to Assess Bacterial Flagellar Motility Near a Surface

Shindell

Nguyen

Coltharp

et al. 2021

Fluids

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The presence of a nearby boundary is likely to be important in the life cycle and evolution of motile flagellate bacteria. This has led many authors to employ numerical simulations to model near-surface bacterial motion and compute hydrodynamic boundary effects. A common choice has been the method of images for regularized Stokeslets (MIRS); however, the method requires discretization sizes and regularization parameters that are not specified by any theory. To determine appropriate regularization parameters for given discretization choices in MIRS, we conducted dynamically similar macroscopic experiments and fit the simulations to the data. In the experiments, we measured the torque on cylinders and helices of different wavelengths as they rotated in a viscous fluid at various distances to a boundary. We found that differences between experiments and optimized simulations were less than 5% when using surface discretizations for cylinders and centerline discretizations for helices. Having determined optimal regularization parameters, we used MIRS to simulate an idealized free-swimming bacterium constructed of a cylindrical cell body and a helical flagellum moving near a boundary. We assessed the swimming performance of many bacterial morphologies by computing swimming speed, motor rotation rate, Purcell’s propulsive efficiency, energy cost per swimming distance, and a new metabolic energy cost defined to be the energy cost per body mass per swimming distance. All five measures predicted that the optimal flagellar wavelength is eight times the helical radius independently of body size and surface proximity. Although the measures disagreed on the optimal body size, they all predicted that body size is an important factor in the energy cost of bacterial motility near and far from a surface.

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Efficient shapes for microswimming: From three-body swimmers to helical flagella

Cited by 19 publications

References 54 publications

Rational design and dynamics of self-propelled colloidal bead chains: from rotators to flagella

Rational design and dynamics of self-propelled colloidal bead chains: from rotators to flagella

Boosting micromachine studies with Stokesian Dynamics

Using Experimentally Calibrated Regularized Stokeslets to Assess Bacterial Flagellar Motility Near a Surface

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