Deformation profiles and microscopic dynamics of complex fluids during oscillatory shear experiments

Edera, Paolo; Brizioli, Matteo; Zanchetta, Giuliano; Petekidis, George; Giavazzi, Fabio; Cerbino, Roberto

doi:10.1039/d1sm01068a

Cited by 9 publications

(15 citation statements)

References 57 publications

(80 reference statements)

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“…A possible reason for this may be stage drift that is present and may create uniaxial motion; this would have an effect on particle movement that only becomes apparent at later response times since the particles’ individual motion would dominate at shorter response times . Dedrifting algorithms have previously been written for MPT and are commonly employed as done so here, whereas DDM is still a relatively new technique and advancements in dedrifting have only recently been made. , For samples that undergo gelation, MSDs determined by MPT and DDM agree at time points prior to the critical gelation point. Some deviation from the MSDs measured by MPT is also observed at the long-term response for DDM, demonstrated by an uptick in the slope toward the end of the measurement.…”

Section: Resultsmentioning

confidence: 99%

“…48 Dedrifting algorithms have previously been written for MPT and are commonly employed as done so here, whereas DDM is still a relatively new technique and advancements in dedrifting have only recently been made. 49,50 For samples that undergo gelation, MSDs determined by MPT and DDM agree at time points prior to the critical gelation point. Some deviation from the MSDs measured by MPT is also observed at the long-term response for DDM, demonstrated by an uptick in the slope toward the end of the measurement.…”

Section: ■ Materials and Methodsmentioning

confidence: 97%

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High-Throughput Microrheology for the Assessment of Protein Gelation Kinetics

et al. 2022

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A high-throughput microrheological assay is employed to assess the gelation kinetics of a coiled-coil protein, Q, across a compositional space with varying ionic strengths and pH values. Two methods of passive microrheologymultiple particle tracking (MPT) and differential dynamic microscopy (DDM)are used to determine mean-squared displacements of tracer beads embedded in protein solutions with respect to lag time over a fixed period. MPT data was analyzed to determine gelation kinetics in a high-throughput, automatable manner by fitting relaxation exponents to sigmoidal curves and verifying with the more traditionally used time-cure superposition. DDM-determined gelation time was assessed as the last resolvable time, which we found to be on a similar scale to gelation times given by MPT. Both methods show distinct advantages with regard to being used in a highthroughput, automatable setup; DDM can serve as an effective initial screen for rapid gelation kinetics due to it requiring less user intervention and inputs, with MPT giving a more complete understanding of the entire gelation process. Using these methods, a clear optimum for rapid gelation was observed near the isoelectric point of Q and at higher ionic strengths over the compositional space studied.

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Section: Resultsmentioning

confidence: 99%

Section: ■ Materials and Methodsmentioning

confidence: 97%

High-Throughput Microrheology for the Assessment of Protein Gelation Kinetics

et al. 2022

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“…One of the most promising applications of this method could be the investigation of the crossover between non-Gaussian to Gaussian behavior as predicted by diffusing diffusivity theories. For example, recent results on periodically sheared yield-stress materials [53] showed the presence of shear-induced diffusion along with a Lorentzian-like relation for the ISF and non-Gaussian PDF of the particle displacements, at least for a relatively short observation time. Reciprocal space investigation of the long-time dynamics of tracers embedded in yield stress-material, while subjected to oscillatory shear deformation, may be a promising way to assess and validate diffusing diffusivity models.…”

Section: Discussionmentioning

confidence: 99%

“…In practice, this procedure is prevented by the fact that Δt is bounded from below by the inverse of the frame rate. We, thus, fit a polynomial function of the second degree to D(q,Δt) over a narrow time interval including the smallest accessible lag-times (typically the first five) and estimate B(q) as the intercept of the best fitting curve [53]. Once B(q) is estimated, we could, in principle, obtain A(q) as the long-time limit of D(q,Δt) − B(q) since f(q,Δt → ∞) → 0.…”

Section: Conddm Analysismentioning

confidence: 99%

Reciprocal Space Study of Brownian Yet Non-Gaussian Diffusion of Small Tracers in a Hard-Sphere Glass

et al. 2022

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The simultaneous presence of normal (Brownian) diffusion and non-Gaussian statistics of particle displacements has been identified as a recurring motif for a broad spectrum of physical and biological systems. While not yet fully understood, it is generally accepted that a key ingredient for observing this Brownian yet non-Gaussian (BNG) diffusion is that the environment hosting the particles appears stationary and homogenous on the small length and time scales, while displaying significant fluctuations on larger distances and/or longer time scales. To date, most of the experimental studies on systems displaying BNG diffusion have been performed in direct space, usually via a combination of optical microscopy and particle tracking to quantify the particle’s self-diffusion. Here, we demonstrate that a reciprocal space analysis of the density fluctuations caused by the particle motion as a function of the wave vector enables the investigation of BNG diffusion in situations where single-particle tracking is impossible. To accomplish this aim, we use confocal differential dynamic microscopy (ConDDM) to study the BNG dynamics of diluted sub-resolution tracers diffusing in a glassy matrix of larger hard spheres. We first elucidate the nontrivial connection between the tracer self-diffusion and collective relaxation of the resulting density fluctuations. We find that the experimentally determined intermediate scattering functions are in excellent agreement with the recent predictions of a “diffusing diffusivity” model of BNG diffusion, whose analytical predictions are available only in reciprocal space. Our results show that studying BNG diffusion in reciprocal space can be an invaluable strategy to access the fast, anomalous dynamics occurring at very small scales in crowded environments.

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“…While the tests presented here are meant to highlight the capabilities of our setup and give an idea of how it could be used, the setup could be pushed further. For instance, remaining in the framework of simple shear oscillation experiments, one could go beyond echo-imaging FIGURE 1 (A) Sketch of the key components of the shear cell: air bearing (1), inlet for compressed air (2), voice coil (3), holder for the upper glass slide (4), support of the lower glass slide (5), mounting base of the shear cell (6), microscope stage (7), clamping system fixing the cell mounting base to the microscope stage (8), ground glass (9), micrometric screws for controlling the gap distance h and the parallelism of the glass slides (10), pass-through hole enabling imaging with the underlying objective (11). The moving part of the shear cell, driven by the voice coil actuator, is composed by the moving parts of (1,3) plus parts (4,9).…”

Section: Introductionmentioning

confidence: 99%

Quantitative rheo-microscopy of soft matter

et al. 2022

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Direct observation of the microscopic material structure and dynamics during rheological shear tests is the goal of rheo-microscopy experiments. Microscopically, they shed light on the many mechanisms and processes that determine the mechanical properties at the macroscopic scale. Moreover, they permit for the determination of the actual deformation field, which is particularly relevant to assess shear banding or wall slip. While microscopic observation of the sample during mechanical probing is achieved by a variety of custom and commercial instruments, the possibility of performing quantitative rheology is not commonly available. Here, we describe a flexible rheo-microscopy setup that is built around a parallel-sliding-plate, stress-controlled shear cell, optimized to be mounted horizontally on a commercial microscope. Mechanically, soft materials with moduli ranging from few tens of Pa up to tens of kPa can be subjected to a variety of waveforms, ranging from standard step stress and oscillatory stress to more peculiar signals, such as triangular waves or any other signal of interest. Optically, the shear cell is designed to be compatible with different imaging methods (e.g. bright field or confocal microscopy). Most of the components of the shear cell are commercially available, and those that are not can be reproduced by a standard machine shop, easing the implementation of the rheo-microscopy setup in interested laboratories.

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Deformation profiles and microscopic dynamics of complex fluids during oscillatory shear experiments

Abstract: Oscillatory shear tests are widely used in rheology to characterize the linear and non-linear mechanical response of complex fluids, including the yielding transition. There is an increasing urge to acquire...

Cited by 9 publications

References 57 publications

High-Throughput Microrheology for the Assessment of Protein Gelation Kinetics

High-Throughput Microrheology for the Assessment of Protein Gelation Kinetics

Reciprocal Space Study of Brownian Yet Non-Gaussian Diffusion of Small Tracers in a Hard-Sphere Glass

Quantitative rheo-microscopy of soft matter

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