Is the Zero Reynolds Number Approximation Valid for Ciliary Flows?

Wei, Da; Dehnavi, Parviz Ghoddoosi; Aubin‐Tam, Marie‐Eve; Tam, Daniel

doi:10.1103/physrevlett.122.124502

Cited by 23 publications

(36 citation statements)

References 30 publications

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“…The presence of several harmonics in the x(t) and y(t) signals leads to reconstructions of the input velocities u x (t) and u y (t) , which significantly differ from x(t) and y(t) in amplitude, shape and phase. To verify the accuracy of the velocimetry method, we compare the OTV measurements with the numerical boundary element method (BEM) simulations (Wei et al 2019). We model the cell body and the pipette as a single axisymmetric object.…”

Section: Case Study: Unsteady Flow Around C Reinhardtiimentioning

confidence: 99%

“…Furthermore, we use slender body theory to represent the flagella. The shapes and deformations of the flagella are directly extracted from the experiment recordings and used in BEM simulations to compute the flow fields (see Wei et al (2019) for more details). In Fig.…”

Section: Case Study: Unsteady Flow Around C Reinhardtiimentioning

confidence: 99%

“…1. This limit is reached for measurements of biological flows, such as those created by ciliated organisms (Wei et al 2019). Here, we present and fully characterize a velocimetry method using optical tweezers and Kalman filtering, which achieves accurate velocimetry measurements below the diffusion limit.…”

Section: Introductionmentioning

confidence: 99%

“…This measurement also confirms the compatibility of OTV with biological flow measurements. This method has been used recently by Wei et al (2019) to measure the unsteady flow around C. reinhardtii. The Matlab implementation of the Kalman filter by EKF/UKF toolbox (Hartikainen et al 2011) is available online through the 4TU.…”

Section: Introductionmentioning

confidence: 99%

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Optical tweezers-based velocimetry: a method to measure microscale unsteady flows

et al. 2020

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In the study of micro-scale biological flows, velocimetry methods based on passive tracers, such as micro-PIV and micro-PTV, are well established to characterize steady flows. However, these methods become inappropriate for measuring unsteady flows of small amplitude, because, on these scales, the motion of passive tracers cannot be distinguished from Brownian motion. In this study, we use optical tweezers (OTs) in combination with Kalman filtering, to measure unsteady microscopic flows with high temporal accuracy. This method is referred to as optical tweezers-based velocimetry (OTV). The OTV method measures the nanometric displacements of a trapped bead, and predicts the instantaneous velocity of the flow by employing a Kalman filter. We discuss the accuracy of OTV in measuring unsteady flows with 1.5–70 $$\upmu$$ μ m s$$^{-1}$$ - 1 amplitudes and 10–90 Hz frequencies. We quantify how the bead size and the laser power affect the velocimetry accuracy, and specify the optimal choices for the bead size and laser power to measure different unsteady flows. OTV accurately measures unsteady flows with amplitudes as small as 3–6 $$\upmu$$ μ m s$$^{-1}$$ - 1 . We compare the accuracy of OTV and micro-PTV, and characterize the flow regime for which OTV outperforms micro-PTV. We also demonstrate the robustness of OTV by measuring the unsteady flow created by the cilia of green alga Chlamydomonas reinhardtii, and comparing with numerical predictions based on Stokes equations. An open-source implementation of the OTV software in Matlab is available through the 4TU.Centre for Research Data. Graphic abstract

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Section: Case Study: Unsteady Flow Around C Reinhardtiimentioning

confidence: 99%

Section: Case Study: Unsteady Flow Around C Reinhardtiimentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Optical tweezers-based velocimetry: a method to measure microscale unsteady flows

et al. 2020

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“…However, previous studies of sensing assumed either oscillatory inviscid flow or steady viscous flow in the far field 14,20,33 and neglected the combined effects of viscosity and inertia in the near field. More recent studies have shown that, even in fluids dominated by viscosity at the microscopic scale, oscillating structures such as cilia have minute inertia yet they can still have profound long-lasting effects, resulting in flows governed importantly by both viscosity and inertia 34,35 . It is precisely the combination of these two effects that can effectively facilitate the detection of inert particles at the edge of a boundary layer, e.g.…”

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confidence: 99%

Active hydrodynamic imaging of a rigid spherical particle

Takagi

Strickler

2020

Sci Rep

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A body with mechanical sensors may remotely detect particles suspended in the surrounding fluid via controlled agitation. Here we propose a sensory mode that relies on generating unsteady flow and sensing particle-induced distortions in the flow field. We demonstrate the basic physical principle in a simple analytical model, which consists of a small spherical particle at some distance from a plate undergoing impulsive or oscillatory motion. The model shows that changes in pressure or shear on the plate can be used to infer the location and size of the sphere. The key ingredient is to produce strong shear or strain around the sphere, which requires careful tuning of the viscous boundary layer on the moving plate. This elucidates how some organisms and devices may control their unsteady dynamics to enhance their range of perception.

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Fibrous Flagellar Hairs of Chlamydomonas reinhardtii Do Not Enhance Swimming

Amador

Wei

Tam

et al. 2020

Biophysical Journal

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The flagella of Chlamydomonas reinhardtii possess fibrous ultrastructures of a nanometer-scale thickness known as mastigonemes. These structures have been widely hypothesized to enhance flagellar thrust; however, detailed hydrodynamic analysis supporting this claim is lacking. In this study, we present a comprehensive investigation into the hydrodynamic effects of mastigonemes using a genetically modified mutant lacking the fibrous structures. Through high-speed observations of freely swimming cells, we found the average and maximum swimming speeds to be unaffected by the presence of mastigonemes. In addition to swimming speeds, no significant difference was found for flagellar gait kinematics. After our observations of swimming kinematics, we present direct measurements of the hydrodynamic forces generated by flagella with and without mastigonemes. These measurements were conducted using optical tweezers, which enabled high temporal and spatial resolution of hydrodynamic forces. Through our measurements, we found no significant difference in propulsive flows due to the presence of mastigonemes. Direct comparison between measurements and fluid mechanical modeling revealed that swimming hydrodynamics were accurately captured without including mastigonemes on the modeled swimmer’s flagella. Therefore, mastigonemes do not appear to increase the flagella’s effective area while swimming, as previously thought. Our results refute the longstanding claim that mastigonemes enhance flagellar thrust in C. reinhardtii , and so, their function still remains enigmatic.

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Is the Zero Reynolds Number Approximation Valid for Ciliary Flows?

Cited by 23 publications

References 30 publications

Optical tweezers-based velocimetry: a method to measure microscale unsteady flows

Optical tweezers-based velocimetry: a method to measure microscale unsteady flows

Active hydrodynamic imaging of a rigid spherical particle

Fibrous Flagellar Hairs of Chlamydomonas reinhardtii Do Not Enhance Swimming

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