Direct Crystal Growth Control: Controlling Crystallization Processes by Tracking an Analogue Twin

Due to the dynamic interactions of various crystallization phenomena, crystallization processes are notoriously difficult to control. In some applications, supersaturation control is aimed for as it affects various phenomena. Direct nucleation control aims at controlling the number of crystals in suspension. Here, we propose direct crystal growth control (DGC). The new method avoids parametrization of the thermodynamic relation between concentration, temperature, and solubility. Instead, a single crystal is fixed in the crystallization vessel, and it acts as an analogue twin. The analogue twin enables inline growth rate measurement and serves as a proxy for the growth of the suspended crystals. Via temperature manipulation, the analogue twin’s growth rate can be controlled to be kept constant. Growth rate of suspended crystals is then observed to be constant, too. However, hydrodynamic conditions for the analogue twin and suspended crystals were different and need to be further explored for a more accurate application of DGC. Temperature-dependent growth rates, the existence of molecular clusters in solution, and the potential use of the new growth rate probe for parameter estimation are discussed.