Rheology and DWS microrheology of concentrated suspensions of the semiflexible filamentous fd virus

Abstract

Microrheology measurements were performed on suspensions of bacteriophage fd with diffusive wave spectroscopy in the concentrated regime, at different values of ionic strength. Viscosity vs. shear rate was also measured, and the effect of bacteriophage concentration and salt addition on shear thinning was determined, as well as on the peaks in the viscosity vs. shear curves corresponding to a transition from tumbling to wagging flow. The influence of concentration and salt addition on the mean square displacement of microspheres embedded in the suspensions was determined, as well as on their viscoelastic moduli up to high angular frequencies. Our results were compared with another microrheology technique previously reported where the power spectral density of thermal fluctuations of embedded micron-sized particles was evaluated. Although both results in general agree, the diffusive wave spectroscopy results are much less noisy and can reach larger frequencies. A comparison was made between measured and calculated shear modulus. Calculations were made employing the theory for highly entangled isotropic solutions of semiflexible polymers using a tube model, where various ways of calculating the needed parameters were used. Although some features are captured by the model, it is far from the experimental results mainly at high frequencies.

Translational and rotational dynamics of colloidal particles in suspension: Effect of shear

“…Equations (9) and (10) constitute extensions of the corresponding FP equations derived by Mayorga et al [22] and Refs. [34,35] for the purely translational motion case of Brownian spheres.…”

“…Due to birefringence measurements, it is known that even at low shear rates [7,8] there occurs phase separation in fd bacteriophage suspensions. Its rheological characterization is currently performed with diffusion wave spectroscopy [9] and optical tweezer microrheology experiments [10]. From the theoretical viewpoint, its rheological properties can be determined through evolution equations derived from the moments of the distribution function that satisfy the system's Fokker-Planck (FP) equation [11].…”

“…The above FP Eqs. (9) and (10) depend on the time-independent friction tensors ζ ij (x N ) and refer to the temporal evolution of the probability density in the internal phase space of configurations and velocities. These FP were derived under the assumption of τ B τ H , which means that hydrodynamic interactions (HI) are instantaneous on time scale τ B since solvent dynamics is completely decoupled from colloids variables.…”

Passive microrheology for measurement of gelation behavior of a kind of polymer gel P(AM‐AA‐AMPS)

“…Latex particles could be embedded in that cage‐type space. With the increase of decorrelation time, MSD curve can be divided into three stages (Figure ): the first stage, the particles could move freely in the cage, the MSD grows linear with the increase of decorrelation time; the second stage, the particles are blocked by the cage wall, thus MSD curve hardly change with the increase of decorrelation time, forming a platform area, which is characteristic of the elasticity of the sample; the third stage, at longer time scales, the particles start to break the cage wall and diffuse into another cage‐type space and the MSD grows as it would for a viscous fluid. This is characteristic of the macroscopic viscosity, as it corresponds to the migration speed of the particles in the sample.…”

Thermoresponsive Chiral to Nonchiral Ordering Transformation in the Nematic Liquid-Crystal Phase of Rodlike Viruses: Turning the Survival Strategy of a Virus into Valuable Material Properties

“…40 o C, independent of the ionic strengths and virus concentrations. This is surprising, since low ionic strength and high virus concentration mean higher viscosity, 37 which might hinder the re-ordering the rod from the chiral arrangement into non-chiral ordering. This probably points to the fact that some intrinsic properties occur to the virus itself around this temperature.…”