An efficient scheme for sampling fast dynamics at a low average data acquisition rate

Philippe, Adrian-Marie; Aime, Stefano; Roger, Valentin; Jelinek, Remi; Prévôt, G.; Cipelletti, Luca

doi:10.1088/0953-8984/28/7/075201

Cited by 18 publications

(13 citation statements)

References 32 publications

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“…Simultaneous video recording and light scattering was performed using another setup equipped with one CCD mounted at an angle of 45° for capturing speckle dynamics and a second CCD at 90° for capturing real-space video. CCD data acquisition was performed using a variable delay between images, as described previously [89]. In brief, we acquired pairs of images: the delay between two pairs of images varied from 5 ms to 1 s using ¼-order-of-magnitude steps, scaled logarithmically (e.g.…”

Section: Dynamic Light Scattering Experimentsmentioning

confidence: 99%

Uncovering the dynamic precursors to motor-driven contraction of active gels

2019

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Cells and tissues have the remarkable ability to actively generate the forces required to change their shape. This active mechanical behavior is largely mediated by the actin cytoskeleton, a crosslinked network of actin filaments that is contracted by myosin motors. Experiments and active gel theories have established that the length scale over which gel contraction occurs is governed by a balance between molecular motor activity and crosslink density. By contrast, the dynamics that govern the contractile activity of the cytoskeleton remain poorly understood. Here we investigate the microscopic dynamics of reconstituted actin-myosin networks using simultaneous real-space video microscopy and Fourier-space dynamic light scattering. Light scattering reveals rich and unanticipated microscopic dynamics that evolve with sample age. We uncover two dynamical precursors that precede macroscopic gel contraction. One is characterized by a progressive acceleration of stressinduced rearrangements, while the other consists of sudden rearrangements that depend on network adhesion to the boundaries and are highly heterogeneous. Our findings reveal an intriguing analogy between self-driven rupture and collapse of active gels to the delayed rupture of passive gels under external loads.

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Section: Dynamic Light Scattering Experimentsmentioning

confidence: 99%

Uncovering the dynamic precursors to motor-driven contraction of active gels

2019

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“…PIV is a well-established method that has been fine-tuned during the years and nowadays can even operate in real-time. By contrast, DDM is still in its young age and real-time analysis has not yet been achieved, even though GPU accelerated versions of the differential dynamic algorithm have been successfully implemented 18,49 , as well as efficient schemes for data sampling that can probe fast dynamics at a low average data acquisition rate 50 . A big limitation of PIV compared to DDM is that, being inherently conceived for assessing velocity, it is not the right tool for mapping disordered forms of motility such as for instance Brownian motion, even though in principle this is possible.…”

Section: Established Points Of Strenghts and Limiting Factorsmentioning

confidence: 99%

Perspective: Differential dynamic microscopy extracts multi-scale activity in complex fluids and biological systems

Cerbino

Cicuta

2017

The Journal of Chemical Physics

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Differential dynamic microscopy (DDM) is a technique that exploits optical microscopy to obtain local, multi-scale quantitative information about dynamic samples, in most cases without user intervention. It is proving extremely useful in understanding dynamics in liquid suspensions, soft materials, cells and tissues. In DDM, image sequences are analyzed via a combination of image differences and spatial Fourier transforms to obtain information equivalent to that obtained by means of light scattering techniques. Compared to light scattering, DDM offers obvious advantages, principally (a) simplicity of setup; (b) possibility of removing static contributions along the optical path; (c) power of simultaneous different microscopy contrast mechanisms; (d) flexibility of choosing an analysis region, analogous to a scattering volume. For many questions, DDM has also advantages compared to segmentation/tracking approaches and to correlation techniques like Particle Image Velocimetry. The very straightforward DDM approach, originally demonstrated with bright field microscopy of aqueous colloids, has lately been used to probe a variety of other complex fluids and biological systems with many different imaging methods, including dark-field, differential interference contrast, wide-field, light-sheet, and confocal microscopy. The number of adopting groups is rapidly increasing and so are the applications. Here, we briefly recall the working principles of DDM, we highlight its advantages and limitations, we outline recent experimental breakthroughs, and we provide a perspective on future challenges and directions. DDM can become a standard primary tool in every laboratory equipped with a microscope, at the very least as a first bias-free automated evaluation of the dynamics in a system.

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“…We measure the dynamics of a suspension of polystyrene particles with diameter 2a = 1.2µm (Invitrogen Molecular Probes), suspended at a weight fraction of 0.01% in a 1:1 v/v mixture of H 2 O and D 2 O that matches the density of polystyrene, to avoid sedimentation. A time series of images of the scattered light is acquired using the scheme described in 91 , both at rest and while imposing a constant shear rate γ = 0.03s −1 . The intensity correlation function is calculated using Eq.…”

Section: Dynamic Light Scattering Under Shearmentioning

confidence: 99%

A stress-controlled shear cell for small-angle light scattering and microscopy

Aime

Ramos

Fromental

et al. 2016

Review of Scientific Instruments

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We develop and test a stress-controlled, parallel plates shear cell that can be coupled to an optical microscope or a small angle light scattering setup, for simultaneous investigation of the rheological response and the microscopic structure of soft materials under an imposed shear stress. In order to minimize friction, the cell is based on an air bearing linear stage, the stress is applied through a contactless magnetic actuator, and the strain is measured through optical sensors. We discuss the contributions of inertia and of the small residual friction to the measured signal and demonstrate the performance of our device in both oscillating and step stress experiments on a variety of viscoelastic materials.

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An efficient scheme for sampling fast dynamics at a low average data acquisition rate

Cited by 18 publications

References 32 publications

Uncovering the dynamic precursors to motor-driven contraction of active gels

Uncovering the dynamic precursors to motor-driven contraction of active gels

Perspective: Differential dynamic microscopy extracts multi-scale activity in complex fluids and biological systems

A stress-controlled shear cell for small-angle light scattering and microscopy

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