Multiple light scattering from disordered media. The effect of brownian motion of scatterers

Maret, Georg; Wolf, P. E.

doi:10.1007/bf01303762

Cited by 673 publications

(495 citation statements)

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“…The motion of probe particles can either be controlled actively, e.g., using optical tweezers or one can analyze the thermal motion of particles to obtain information about the viscoelastic properties of the surrounding fluid. The latter can be achieved by using diffusing wave spectroscopy (DWS) [6]. DWS provides a fast ensemble average of the tracer motion and can resolve extremely fast displacements on the order of microseconds with subnanometer resolution.…”

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confidence: 99%

Broad Bandwidth Optical and Mechanical Rheometry of Wormlike Micelle Solutions

et al. 2007

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We characterize the linear viscoelastic shear properties of an aqueous wormlike micellar solution using diffusing wave spectroscopy (DWS) based tracer microrheology as well as various mechanical techniques such as rotational rheometry, oscillatory squeeze flow, and torsional resonance oscillation covering the frequency range from 10 ÿ1 to 10 6 rad=s. Since DWS as well as mechanical oscillatory squeeze flow and torsional resonance oscillation cover a sufficiently high frequency range, the persistence length of wormlike micelles could be determined directly from rheological measurements for the first time.PACS numbers: 83.80. Qr, 82.70.ÿy, 83.60.Bc, 83.85.Ei Significant progress has been made over the past decade in developing optical microrheology as a noninvasive means to study the rheological properties of soft complex fluids. Following the seminal Letter of Mason and Weitz in 1995 [1], several hundred studies have reported on the application of optical microrheology to such diverse systems as polymers, emulsions, gels, biomaterials, hydrogel scaffolds, stomach mucus, magnetic fluids, ceramics, slurries, and many more [1][2][3][4][5]. The underlying idea is to study the response of small (colloidal) particles embedded in the system under study. The motion of probe particles can either be controlled actively, e.g., using optical tweezers or one can analyze the thermal motion of particles to obtain information about the viscoelastic properties of the surrounding fluid. The latter can be achieved by using diffusing wave spectroscopy (DWS) [6]. DWS provides a fast ensemble average of the tracer motion and can resolve extremely fast displacements on the order of microseconds with subnanometer resolution. Despite the large literature, benchmarking optical microrheological techniques with macroscopic mechanical measurements is still not concluded. Almost all comparisons between microrheology and macrorheology have been restricted to the frequency range <10 2 rad=s due to mechanical limitations and inertial effects in the gap loading limit of conventional rotational rheometers and the limited availability of mechanical devices operating at higher frequencies [7][8][9].Here we apply both DWS and macroscopic mechanical rheometry to characterize an aqueous solution of cetylpyridinium chloride and sodium salicylate (100mM CPyCl-60mM NaSal) at different temperatures. These solutions display complex viscoelastic properties but are easy and reproducible to prepare and stable in time. They exhibit fast dynamics and the structural features are much smaller than the tracer particles. The latter is an important requirement for the successful application of tracer microrheology which might otherwise lead to erroneous results [4]. Because of the peculiar viscoelastic behavior such systems have found wide commercial application ranging from personal care to enhanced oil recovery products [10]. Rapid access to microscopic structural and dynamic properties is therefore of interest both from a fundamental and an applied point of vi...

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Broad Bandwidth Optical and Mechanical Rheometry of Wormlike Micelle Solutions

et al. 2007

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“…Before discussing the results, we will discuss the basis of diamagnetic levitation and the potential landscape for residual accelerations in our setup [19,20], as well as the fundamentals of DWS with an emphasis on multi-speckle DWS [14,15,17]. Then we will present results on the averaged dynamics, which corresponds well with our earlier results on the transition in coarsening dynamics [10].…”

Section: Introductionmentioning

confidence: 81%

“…Diffusing wave spectroscopy is a version of dynamic light scattering that can be applied to multiply scattering samples and gives information about movements on the nm-scale in such samples [14,15]. For this purpose, we illuminate the sample with a Coherent Verdi CW laser at a wavelength of 532 nm and a power of 100 mW.…”

Section: Diffusing Wave Spectroscopymentioning

confidence: 99%

“…Recently, we qualitatively changed leading to a liquid like behaviour of the foam. Here, we will address the question of the local bubble dynamics in diamagnetically levitated dry and wet foams using diffusing wave spectroscopy (DWS) [14,15,8]. In particular using multi-speckle DWS [18] based on a fast camera, we are studying the time dependence of local movement of the scatterers on time scales of several seconds [17].…”

Section: Introductionmentioning

confidence: 99%

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Studying foam dynamics in levitated, dry and wet foams using diffusing wave spectroscopy

Isert

Maret

Aegerter

2015

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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h i g h l i g h t s• Coarsening dynamics of foams studied by multi-speckle diffusing wave spectroscopy.• Magnetic levitation allows a large range of liquid fractions to be studied for hours.• Cross over from Neumann to Ostwald regime at liquid fraction around 30%.• In dry foams intermittent bursts of activity signal collective bubble rearrangements.• In wet foams bubbles move ballistically with random collisions. t r a c tWe use diffusing wave spectroscopy to study the microscopic dynamics of foams. These foams are levitated diamagnetically, such that very high liquid fractions can be achieved. We find that at low liquid fraction the dynamics is dominated by local rearrangements, whereas at high liquid fraction the movement of bubbles is ballistic and large scale rearrangements are absent. This change in the microscopic dynamics coincides with a change in the scaling of coarsening on increasing the liquid fraction that we have found earlier.

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“…Rather than attempting an absolute calibration of d 2 (t, τ) we have chosen to take the initial state of the experiment, d 2 (t = 0), as a reference. The scattering geometry in our experiment is similar to the one used in traditional backscattering variant of DWS except for the fact that we are studying speckle fluctuations in the image plane [23][24][25]. Speckles in the image plane are often referred to as near field speckles [26] which must not be confused with the optical near field of evanescent waves probed for example with scanning near field optical microscopy [27].…”

Section: Methodsmentioning

confidence: 99%

Monitoring Spatially Heterogeneous Dynamics in a Drying Colloidal Thin Film

Zakharov

Scheffold

2010

Soft Materials

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We report on a new type of experiment that enables us to monitor spatially and temporally heterogeneous dynamic properties in complex fluids. Our approach is based on the analysis of near-field speckles produced by light diffusely reflected from the superficial volume of a strongly scattering medium. By periodic modulation of an incident speckle beam we obtain pixel-wise ensemble averages of the structure function coefficient, a measure of the dynamic activity. To illustrate the application of our approach we follow the different stages in the drying process of a colloidal thin film. We show that we can access ensemble averaged dynamic properties on length scales as small as ten micrometers over the full field of view.

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Multiple light scattering from disordered media. The effect of brownian motion of scatterers

Cited by 673 publications

References 14 publications

Broad Bandwidth Optical and Mechanical Rheometry of Wormlike Micelle Solutions

Broad Bandwidth Optical and Mechanical Rheometry of Wormlike Micelle Solutions

Studying foam dynamics in levitated, dry and wet foams using diffusing wave spectroscopy

Monitoring Spatially Heterogeneous Dynamics in a Drying Colloidal Thin Film

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