Building a DLS Device to Measure In Situ Glycine Cluster Formation*

Laser trapping nucleation uses optical tweezers focused at the air-solution interface to grow crystals. Research has shown that focusing a continuous wave (CW) laser at the glass-solution interface of a solution of glycine in deuterium oxide, does not lead to nucleation, but to laser-induced phase separation (LIPS) droplet formation. The LIPS droplet is about double the concentration of the initial solution, past the metastable zone. This droplet is believed to be made up of large, liquid-like clusters of glycine that are organized in a size gradient with larger clusters in the center of the solution.
Minutes after the LIPS droplet relaxes over a few minutes, clusters in the LIPS droplet spontaneously organize into a critical nucleus. Microscopic demixing of the solution is believed to leads to the observed polymorph-selectivity for LIPS droplet-grown crystals. To better understand the LIPS droplet, a dynamic light scattering (DLS) device will be constructed to observe the LIPS droplet in situ. By measuring the hydrodynamic radius of the glycine particles in situ, one can better understand this crystal growth mechanism.