Heterodyne near-field scattering: A technique for complex fluids

Abstract

We implemented the heterodyne near-field scattering (HNFS) technique [Appl. Phys. Lett. 81, 4109 (2002)]], showing that it is a fairly valid alternative to traditional elastic low-angle light scattering and quite suitable for studying complex fluids such as colloidal systems. With respect to the original work, we adopted a different data reduction scheme, which allowed us to improve significantly the performance of the technique, at levels of sensitivity and accuracy much higher than those achievable with classical low-angle light scattering instrumentation. This method also relaxes the requirements on the optical/mechanical stability of the experimental setup and allows for a real time analysis. The HNFS technique has been tested by using calibrated colloidal particles and its capability of performing accurate particle sizing was ascertained on both monodisperse and bimodal particle distributions. Nonstationary samples, such as aggregating colloidal solutions, were profitably studied, and their kinetics quantitatively characterized.

SODI-COLLOID: A combination of static and dynamic light scattering on board the International Space Station

“…The NFS optical layout substantially follows what is described in Ref. 5 and references therein (see Fig. 1).…”

“…[3][4][5] In contrast to usual far-field light scattering measurements, in NFS, light scattered by the sample is recorded at a close distance, together with the transmitted light beam (heterodyne configuration). The advantage is that a large range of scattering angles can be recorded simultaneously.…”

Mass transport properties of the tetrahydronaphthalene/n-dodecane mixture measured by investigating non-equilibrium fluctuations

“…The optical technique we employed is known as Near-Field Scattering [36][37][38][39][40][41][42][43][44][45] by means of a shadowgraph setup [46][47][48]. The shadowgraph optical setup involves a low coherence light source (Super Lumen Diodes, Broad Lighter S680) connected with a single-mode fiber whose output is collimated by an achromatic doublet lens ( f = 15 cm, φ = 5 cm).…”

A new particle sizing technique based on near field scattering

“…(1) it immediately appears that, being the scattered contributions E S changing with time, it is possible to obtain and then get rid of the static stray light contributions contained in E 0 (see [1,3] for more details). As a result, we turn out with the spatial distribution of the amplitude of the scattered field, i(x,y), that is the signal to be analysed.…”

“…In general, the size range of interest spans from fractions to hundreds of microns. Here we focus our attention on the optical methods for particle sizing, and we describe a new technique that we have recently developed and characterized [1] to perform particle sizing in this range. It is based on recent studies about the so called near field speckles [2,3].…”