The younger flagellum sets the beat for Chlamydomonas reinhardtii

Eukaryotes swim with coordinated flagellar (ciliary) beating and steer by fine-tuning the coordination. The model organism for studying flagellate motility, Chlamydomonas reinhardtii, employs synchronous, breaststroke-like flagellar beating to swim, and it modulates the beating amplitudes differentially to steer. This strategy hinges on both...

High-speed imaging of giant unilamellar vesicle production in cDICE

Three-dimensional numerical study of the combined stroke swimmer

A three-dimensional (3D) numerical simulation was performed using a combined stroke swimmer (deformable sphere) in an incompressible fluid of an infinite domain. The time-dependent deformation of the swimmer surface was assumed independent of the circumferential cross section in the flow direction of the swimmer. The 3D numerical simulation...

Hydrodynamic shear dissipation and transmission in lipid bilayers

Vital biological processes, such as trafficking, sensing, and motility, are facilitated by cellular lipid membranes, which interact mechanically with surrounding fluids. Such lipid membranes are only a few nanometers thick and composed of a liquid crystalline structure known as the lipid bilayer. Here, we introduce an active, noncontact, two...

Hopping trajectories due to long-range interactions determine surface accumulation of microalgae

The accumulation of motile cells at solid interfaces increases the rate of surface encounters and the likelihood of surface attachment, leading to surface colonization and biofilm formation. The cell density distribution in the vicinity of a physical boundary is influenced by the interactions between the microswimmers and their physical...

Measurements of the unsteady flow field around beating cilia

The swift deformations of flagella and cilia are crucial for locomotion and fluid transport on the micron scale. Most hydrodynamic models of flagellar and ciliary flows assume the zero Reynolds number limit and model the flow using Stokes equations. Recent work has demonstrated that this quasi-steady approximation breaks down at increasing...

Fibrous Flagellar Hairs of Chlamydomonas reinhardtii Do Not Enhance Swimming

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...

Calibration of multiple cameras for large-scale experiments using a freely moving calibration target

Abstract: Obtaining accurate experimental data from Lagrangian tracking and tomographic velocimetry requires an accurate camera calibration consistent over multiple views. Established calibration procedures are often challenging to implement when the length scale of the measurement volume exceeds that of a typical laboratory experiment. Here,...

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

Abstract: 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...

Ψ -PIV: a novel framework to study unsteady microfluidic flows

Abstract: In microscopic particle image velocimetry (micro-PIV), correlation averaging over multiple frames is often required, leading to a loss in temporal resolution, therefore limiting the measurement accuracy for unsteady flows. Here, we present a new PIV method suitable to study steady and unsteady laminar flows between parallel plates ...

Is the zero Reynolds number approximation valid for ciliary flows?

Stokes equations are commonly used to model the hydrodynamic flow around cilia on the micron scale. The validity of the zero Reynolds number approximation is investigated experimentally with a flow velocimetry approach based on optical tweezers, which allows the measurement of periodic flows with high spatial and temporal resolution. We find...

Analysis of centrifugal homogenization and its applications for emulsification & mechanical cell lysis

We detail the analysis of centrifugal homogenization process by a hydrodynamic model and the model-guided design of a low-cost centrifugal homogenizer. During operation, centrifugal force pushes a multiphase solution to be homogenized through a thin nozzle, consequently homogenizing its contents. We demonstrate and assess the homogenization...

Artificial cell membranes interfaced with optical tweezers: A versatile microfluidics platform for nanomanipulation and mechanical characterization

Cell lipid membranes are the site of vital biological processes, such as motility, trafficking, and sensing, many of which involve mechanical forces. Elucidating the interplay between such bioprocesses and mechanical forces requires the use of tools that apply and measure piconewton-level forces, e.g., optical tweezers. Here, we introduce the...

Scalar mixing in a turbulent boundary layer

We present results on the analysis of measurements on the dispersion of a contaminant in a turbulent boundary layer. The contaminant is a fluorescent dye (Rh.-B) that was introduced in a turbulent boundary layer (푅푅푒푒# = 3050) in a water channel. The velocity field was measured by means of tomographic PIV. Simultaneously, the concentration field...

Ψ-PIV: A novel framework to study unsteady microfluidic flows

In micro-PIV, reaching the optimum image density has always been difficult due to high displacement gradient, coagulation of particles at the inlet and due to particles adhering to the surface to name a few. The most widely used method is to take ensemble correlation average of multiple PIV images to extract the velocity field. However, this...

Multiple-view camera calibration for large scenes with limited spatial access at the Rotterdam Zoo

Obtaining accurate experimental data from Lagrangian tracking and tomographic velocimetry requires an accurate and consistent camera calibration over multiple views. At length-scales that span beyond the laboratory environment obtaining a camera calibration can be challenging. Combining tools developed in computer vision and non-linear camera...

Hydrodynamics Versus Intracellular Coupling in the Synchronization of Eukaryotic Flagella

The influence of hydrodynamic forces on eukaryotic flagella synchronization is investigated by triggering phase locking between a controlled external flow and the flagella of C. reinhardtii. Hydrodynamic forces required for synchronization are over an order of magnitude larger than hydrodynamic forces experienced in physiological conditions. Our...