The role of crystallization, dewetting, and contact angle in the formation of high aspect ratio crystals*

High aspect ratio crystals have many applications including improved delivery of important ingredients in consumer products. We present a process to produce crystals with a controllable aspect ratio using just oil and water in an easily scalable process. When an oil in water emulsion crystallizes, generally crystallization occurs so quickly the droplets do not deform. By adding surfactants the remaining liquid fraction can be forced to eject the crystals as they grow resulting in an elongated crystal. The contact angle the oil droplet makes with the crystal does not remain constant during this process. The rate of dewetting can be tuned by varying the surfactant concentration. The rate of crystallization can be controlled by vary how quickly the system cools. We examine the crystallization and dewetting behaviors by using a non-equilibrium Monte Carlo model. We examine the behavior of the contact angle using a semi-analytical geometric model. Our results give insight into how the contact angle changes and the dependence of the final crystal morphology on the dewetting and crystallization rates.