Diffusing-wave spectroscopy

Foam rheology has been a challenging area of research of interest for the yield behavior and stick-slip flow behavior (see the review by Kraynik [229]). Recent studies by Durian and co-workers combine simulations [230] and a dynamic light scattering technique suited to turbid systems [231], diffusing wave spectroscopy (DWS), to characterize coarsening and shear-induced rearrangements in foams. The dynamics follow stick-slip behavior similar to that found in earthquake faults and friction (see Section XU-2D). 

Although NMRI is a very well-suited experimental technique for quantifying emulsion properties such as velocity profiles, droplet concentration distributions and microstructural information, several alternative techniques can provide similar or complementary information to that obtained by NMRI. Two such techniques, ultrasonic spectroscopy and diffusing wave spectroscopy, can be employed in the characterization of concentrated emulsions in situ and without dilution [45],... 

Y. Hemar, D. N. Pinder, R. J. Hunter, H. Singh, P. Hebraud, D. S. Home 2003, (Monitoring of flocculation and creaming of sodium-caseinate-stabilized emulsions using diffusing-wave spectroscopy), /. Colloid Interface Sd. 264, 502. 

Y. Nicolas, M. Paques, A. Knaebel, A. Steyer, J.-P. Munch, T. B. J. Blijdenstein, G. A. van Aken 2003, (Microrheology structural evolution under static and dynamic conditions by simultaneous analysis of confocal microscopy and diffusing wave spectroscopy), Rev. Sci. Instrum. 74, 3838. 

Slow release rates and remarkable long shelf-life (months) were obtained compared to typical multiple emulsions stabilized by two short surfactants (SMO and polyoxyethylene (20) sorbitan monolaurate). Finally, the long lifetime of the emulsions allowed study via diffusing wave spectroscopy (DWS) of the interactions between the droplets and the globule surface [37],... 

Alexander, M., Dalgleish, D.G. (2007). The interaction of casein micelles with K-carra-geenan studied by diffusing wave spectroscopy. Food Hydrocolloids, 21, 128-136. 

FIG. 5.1 Multiple scattering is viewed as a random walk of the photon in diffusing wave spectroscopy (DWS). 

Chu 1991 Schmitz 1990). For example, the dynamic version of the diffusing wave spectroscopy described in Vignette V is a form of DLS, although in diffusing wave spectroscopy the method of analysis is different in view of multiple scattering. Most of the advanced developments are beyond the scope of this book. However, DLS is currently a routine laboratory technique for measuring diffusion coefficients, particle size, and particle size distributions in colloidal dispersions, and our objective in this section is to present the most essential ideas behind the method and show how they are used for particle size and size distribution measurements. 

Weitz, D. A., and Pine, D. J., Diffusing-Wave Spectroscopy. In Dynamic Light Scattering The Method and Some Applications (W. Brown, Ed.), Clarendon Press, Oxford, England, 1993. 

Alexander, M., Corredig, M., and Dalgleish, D.G. (2006). Diffusing wave spectroscopy of gelling food systems the importance of the photon transport mean free path (I ). Food Hydrocolloids. 20, 325-331. 

Dalgleish, D., Alexander, M., and Corredig, M. (2004). Studies of the acid gelation of milk using ultrasonic spectroscopy and diffusing wave spectroscopy. Food Hydrocolloids. 18, 747-755. 

Hemar, Y., Hebraud, P., Sarcia, R., and Pinder, D.N. (2004). Diffusing-wave spectroscopy of gelling dairy systems. AIP Corf. Proc. 708,434-435. 

Hemar, Y., Singh, H., and Home, D.S. (2004). Determination of early stages of rennet-induced aggregation of casein micelles by diffusing wave spectroscopy and rheological measurements. Curr. Appl. Phys. 4,362 365. 

Vasbinder, A.J., van Mil, P.J.J.M., Bot, A., and de Kruif, K.G. (2001). Acid-induced gelation of heat-treated milk studied by diffusing wave spectroscopy. Colloids Surf. B. 2, 245-... 

Diffusing wave spectroscopy, used to measure statistics of fluctuations in relatively thin, Hele-Shaw configurations... 

Concentrated Dispersions Photon Cross-Correlation Techniques, Fiber-Optics DLS, and Diffusing Wave Spectroscopy... 

FIGURE 5.75 Diffusion wave spectroscopy (DWS). The light reaches the detector after multiple acts of scattering from dispersed particles. The optical path of the hght in the dispersion is modeled as a result of random diffusion motion. Forward (a) or backward (b) scattered hght can be analyzed. 

Unfortunately, because of space, we have not covered important new developments in light scattering for the study of nontransparent systems such as diffusion wave spectroscopy (DWS), fiber-optic quasi-elastic light scattering (FOQELS), dual-color cross-correlation, 3D crosscorrelation DLS, and improved techniques followed from these techniques [1-4]. 

Martiel I, Sagalowicz L, Mezzenga R. Viscoelasticity and interface bending properties of lecithin reverse wormlike micelles studied hy diffusive wave spectroscopy in hydrophobic environment. Langmuir. 2014 30(35) 10751-10759. 

Then the gradual floe destruction produces a shear-thinning behavior, until no Hoes remain but single particles, and the flow becomes Newtonian. In fact, the motion of the droplets under oscillatory strains has been observed by means of diffusing wave spectroscopy (31). Near the yield point, only a small fraction of drops flow while the rest remain as solid blocks. 

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