An apparatus for dynamic viscoelasticity measurement using laser particle tracking

Abstract

An apparatus for dynamic viscoelasticity measurements was developed using laser particle tracking method (LPT). LPT measures the position of micron-sized probe particles embedded in the material. The power spectrum density (PSD) is calculated from the displacement of the probe particle due to Brownian motion, and then the complex modulus is determined from PSD. This method is useful for studying viscoelastic properties at high frequency region in addition to investigating local viscoelastic properties of materials. The apparatus was calibrated with pure water and ethyleneglycol. The complex shear modulus for aqueous solution of wormlike micelles in high frequency regime was measured. The complex shear modulus obtained by LPT showed a good agreement with the results obtained by a conventional rheometer and the fow birefringence measurement, indicating the reliability of the apparatus. © 2010 The Society of Rheology, Japan.