Non-photochemical laser-induced nucleation (NPLIN) is a crystallisation method in which a highly structured phase is formed out of solution by exposure to a laser beam. NPLIN offers unprecedented spatiotemporal control and characterisation of nucleation. NPLIN is energy efficient compared to conventional crystallisation methods and can be implemented in continuous microfluidic reactors, enabling sustainable operation. However, its working principles are not yet fully understood. This study contains an evaluation of four proposed mechanisms and a description of an experimental setup involving an ultrahigh speed camera. Two mechanisms describe interaction of molecular polarisation with the electric field, either isotropically known as dielectric polarisation (DP), or anisotropically via the optical Kerr effect (OKE). The other two mechanisms involve cavitation bubble formation by nanoparticle heating through light absorption. This work contains a refined description of this so-called cavity-induced nucleation where its consequences are distinguished into two mechanisms, either based on concentration enhancement (CICEN) or due to pressure enhancement (CIPEN). Novel theoretical calculations in conjunction with experimental data suggest that NPLIN phenomena are based on DP or CICEN, potentially operating in concert. It is conjectured that the influence of DP and
CICEN can be quantified further by development of a topological description of DP, simulations of CICEN and relating nucleation probabilities to the metastable zone width of various solutes. The calculations suggest that OKE and CIPEN have little significance because involved energies are several orders of magnitude
below kBT . The proposed setup allows for observing the NPLIN phenomena and establishing dependence on cavitation bubbles, providing empirical validation. Solutions to experimental problems are provided, including reduction of sample fluid evaporation, aligning the nucleation site with the region of interest of the camera and removing image noise.

Non-photochemical laser-induced nucleation (NPLIN) is a process where a crystalline phase is formed out of solution by exposure to a laser beam. In NPLIN, the nucleation probability is strongly dependent on the beam intensity and weakly dependent on the wavelength. NPLIN offers a feasible alternative to energy-intensive industrial crystallisation methods. Although several mechanisms have been proposed, little is known about NPLIN at the molecular level. Some theories suggest that nucleation rates are enhanced through the heating of nanoparticles by absorption of electromagnetic energy. In this work, molecular dynamics simulations are performed on the clustering of ions in the vicinity of a heated nanoparticle in an aqueous supersaturated KCl solution. The spherical symmetry of a spherical nanoparticle in solution is exploited by modelling a laterally periodic water column of an initial length of 500 Angstrom enclosed between a planar iron(III) oxide nanoparticle surface and a graphene piston. A cavitation bubble is formed after nanoparticle heating, leading to an increase of clustered ions according to a bond order criterion. The clustering should correspond to nucleation in experimental systems because the clusters satisfy Delta G < 0 for locally valid NPT ensembles. The results corroborate concentration based NPLIN mechanisms as the clustering is visibly induced by local solute evaporation. Pressure based mechanisms appear ineffective because no effects of pressure waves are observed. Thermostatting the graphene sheet does not yield observable dissipation of the thermal energy generated through the nanoparticle heating and at the ion clustering sites and, obstructing completion of the cavitation cycle at a feasible simulation duration. It is suggested to repeat the simulations using a conically shaped system and a piston of higher transverse thermal conductivity.