8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

Tue 611:23-14:00P9.73Real-time monitoring of complex moduli frommicro-rheologyTaiki Yanagishima 11 Biological and Soft Systems Sector, Cavendish Laboratory, JJ Thomson Ave, CB30HE,Cambridge, United KingdomWe describe an online method for analyzing passive micro-rheology data from complex fluidswhich allows real-time monitoring of frequency dependent complex moduli [1], G”(ω). The mostcommon way to convert displacement data into moduli requires a Kramers-Kronig transformation[2], introducing high frequency artifacts, and necessitating the predetermination of experimentduration. We instead implement an online multi-scale correlation, and use a transformationmethod which preserves experimental noise [3]. The resulting algorithm is fast, simple, usesvery little data storage and is artifact free. Firstly, it was applied to a kinetic Monte Carlosimulation of a spherical particle in a harmonic potential, approximating an optical tweezers/ particle tracking measurement [4]. Good agreement was found with theoretically predictedmoduli. High frequency artifacts were not observed, and the coarse-graining did not introduce anyadditional effect. Secondly, experimental data obtained using optical tweezers, silica microspheresand solutions of polyethylene glycol at different concentrations were similarly analysed. Goodagreement was seen with tabulated viscosities and also with bulk rheology measurements.[1] Yanagishima T, Frenkel D, Kotar K and Eiser E 2011 J Phys: Condens Matt accepted[2] Schnurr B, Gittes F, Mackintosh F C and Schmidt C F 1997 Macromolecules 30 7781[3] Evans R M L, Tassieri M, Auhl D and Waigh T A, 2009 Phys Rev E 80 8[4] Gardel M L, Valentine M T and Weitz D A, Ed. Breuer K 2005 Microscale DiagnosticTechniques (Berlin: Springer Verlag)73