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Two-point particle tracking microrheology of nematic complex fluids
Manuel Gómez-González1, Juan C Del Álamo2
1Mechanical & Aerospace Engineering Department, University of California San Diego, 9500 Gilman Dr., La Jolla, CA 92093-0411, USA. manu@ucsd.edu.
Soft Matter
|June 9, 2016
Summary
This study introduces directional two-point particle-tracking microrheology (D2PTM) to measure anisotropic viscoelastic coefficients in complex fluids. D2PTM accurately characterizes nematic materials like liquid crystals and F-actin solutions.
Area of Science:
- Soft Matter Physics
- Rheology
- Biophysics
Background:
- Complex fluids with aligned microstructures, such as liquid crystals and biopolymer networks, exhibit nematic mechanical properties.
- Existing microrheological techniques are insufficient for measuring directional viscoelastic coefficients in these anisotropic materials.
- Microscopic amounts of these materials necessitate sensitive measurement techniques.
Purpose of the Study:
- To develop and validate a novel microrheology technique, directional two-point particle-tracking microrheology (D2PTM), for quantifying anisotropic viscoelastic coefficients.
- To establish the theoretical framework for D2PTM by analyzing particle motion and interactions in nematic complex fluids.
- To demonstrate the capability of D2PTM in characterizing the directional viscoelastic properties of soft materials.
Main Methods:
- Theoretical formulation of D2PTM based on generalized two-point particle tracking microrheology for nematic fluids.
- Numerical simulations of Brownian motion in nematic viscoelastic fluids to test D2PTM accuracy.
- Experimental validation using a lyotropic nematic liquid crystal and nematic F-actin solutions.
Main Results:
- D2PTM accurately recovers prescribed directional frequency-dependent shear moduli in simulations.
- Experimental validation with a lyotropic nematic liquid crystal shows agreement with dynamic light scattering measurements.
- Successful application of D2PTM to characterize nematic F-actin solutions, marking the first microrheological measurement of their directional viscoelastic coefficients.
Conclusions:
- D2PTM is a robust and accurate method for determining anisotropic viscoelastic coefficients in nematic complex fluids.
- The technique provides essential insights into the mechanical behavior of soft materials with microstructural alignment.
- D2PTM opens new avenues for characterizing a range of anisotropic soft materials previously inaccessible to microrheology.
