Microemulsion droplets in optical traps

The rates of phase separation of microemulsion increase near the coverglass, which absorbs the laser more strongly. Conversely, substitution with heavy water reduces the absorptive heating, whilst maintaining a similar refractive index contrast. Localised laser heating is found to be the major driving force behind phase separation. The observed changes are rationalised in terms of the phase diagram of the microemulsion and the value of the amphiphilic ratio. The relative importance and origin of the thermal and optical effects on phase separation are discussed.