PrEdicting Nucleation to support next-generation microtechnology: Diffuse Interface, fluctuating hydrodynamics and rare events.

There is a noticeable trend in simulations of fluid processes to try to be as much as possible multiscale, i.e. to carry out simulations from molecular scale to hydrodynamics. This is made possible by the unprecedented capabilities of parallelization, GPUs, and supercomputing in general, which allow in-silico representation of fluids with billions of degrees of freedom. Despite this formidable scientific progress, one crucial aspect still hinders a quantitative description of phase transitions: the way a phase change originates, namely the nucleation process. The elusiveness of this process stems from its strong multiscale nature, involving both atomistic and hydrodynamic scales. More importantly, as nucleation is a rare event, it inherently involves a broad spectrum of time scales, the most ambitious feature to be characterized. It is also clear that the next technological breakthroughs in phase-change-based microtechnology are limited by the inadequate comprehension of phase transitions. As a matter of fact, the fluid dynamic design of frontier microtechnologies is mainly based on empirical ground. Promising two-phase cooling strategies for microelectronics, phase-change-driven micro-robots, synthetic micro-trees, and bio-inspired microstructures for condensation control are typical examples. Meeting these fundamental and technological needs, the objective of E-Nucl is to provide a holistic understanding of phase change processes in fluids which shall describe both the nucleation inception and its coupling with multiphase hydrodynamics. Pursuing this goal, E-Nucl advocates a paradigm shift in fluid modelling by combining innovative rare-event techniques based on Large Deviation Theory with the Diffuse Interface and Fluctuating Hydrodynamics modelling of multiphase flows. This framework could be a game changer in multiphase fluid dynamics and it will allow the first in-silico high-fidelity trials of archetypal microtechnologies.