Diffusing Wave (DWS)

Diffusing Wave Spectroscopy is a special technique that I once heard described as optics (and maths) for consenting adults!

Diffusing WaveDWS is Dynamic Light Scattering (DLS) extended to opaque media. DLS is well known for its ability to measure Brownian motion of particles in a diluted media in order to determine their particle size (Stokes-Einstein equation). In a DWS experiment, light is scattered several times by a higher concentration of particles as shown in the diagram and these can constuctively or destructively interfere. Unlike DLS where we have a simple PM detector with DWS we can study their formation on the multipixel detector.

This approach enables scientists to probe particle displacement so analyse the viscoelastic properties of complex  fluids.

As ever Wikipedia has an article of some merit, in this case quite limited, to introduce the principle.

Video of DWS principles

DWS with drying films