Particle mobility, optical transient

Recently, great strides have been made in developing electrical and optical transient methods for measuring particle charge and mobility in these nonaqueous dispersions. It has been possible to obtain particle charge/mass ratios as well as the field dependence of particle mobility. 

Figure 4. Experimental setup for determination of particle mobility using both optical and electrical transients (10).

Most colloids are polydisperse in terms of their particle size and charge and thus a single sample exhibits a distribution of mobilities. In principle the above mentioned techniques, in particular optical transients, quasielastic velocimetry in the frequency regime, crossbeam and rotating grating velocimetries, can measure the mobility distribution of a polydisperse colloid. 

Figure 6. Electrical transient from LC colloid corresponding to the optical transient in Figure 5. Solid line is based on calculations using an estimate of ionic mobility and the particle mobilities determined by optical transients. (Reproduced, with permission, from Ref. 29.)...

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