Given the dynamics of non-equilibrium colloidal self-assembly in solution, we need to lock the assembly, to further characterize it. This is the concept of the proposed method FRAME (Fixation and Resolution of colloidal Active Matter Ensembles). The speed of the polymerization process is crucial to ensure that the structure is "instantaneously" locked in place and remains unchanged. Because of this and its high water-solubility, low extinction coefficient and strong UV-absorption at 375 nm, lithium phenyl (2,4,6-trimethylbenzoyl) phosphinate (LAP) was selected as a radical photoinitiator. A UV-365 LED was chosen to maximize UV absorption, and we found that an intensity of 25 mW/cm² was ideal for rapid photopolymerization (Figure ).