Triggerable temperature sensitive microcapsules. Controlled coalescence of inner drops inside double emulsions, drops inside of drops, is useful for triggering chemical reactions inside drops with the outer drop serving as a reaction vessel. Using double emulsions as micro-reactors is one of our reasons for encapsulating different types of inner drops inside another drop.
Coalescence of inner drops is triggered with heat from a heat gun as seen in this video. The outer drop is made of wax using a melt emulsification technique. As the wax melts, the inner aqueous droplets are free to rotate and move around until they come into contact with one another. Prior to drops coalescing, a small bridge is formed between drops. This is noticeable in the video. The video is taken with a high speed camera and played back at a much slower rate. (Credits: L. L. A. Adams , Soft Matter)