Abstract
We develop a new laser Doppler measurement system for the evaluation of the dispersion stability of micro- and nano-emulsions with a spatial resolution in the range of nanometers. In future thermal managements, colloids in the form of micro- and nano-emulsions will play a major role of storing and transporting thermal energy produced by renewable energy source or energy waste. With the emulsions made of phase-change materials, a higher efficiency heat exchange can be achieved through latent heat compare to the sensible one. An important issue of the technology is the dispersion stability of emulsions under repeated phase changes (heat is stored in melting and released in solidification). The dispersion is achieved by the interaction of electrokinetic forces acting on the colloidal particles characterized by zeta potential. We use evanescent waves for measuring the zeta potential of emulsions at thermal interfaces. The use of evanescent waves can achieve a spatial resolution in the range of nanometers, which is never feasible with a conventional optical system bounded by the diffraction limit. We present the basic concept and the prototype design of the measurement system.
