Cellular modelling of the laser-induced forward transfer of micro - and nano-scale droplets

Xu, X., Banks, D.P., Eason, R.W. and Banks, S.P. (2009) Cellular modelling of the laser-induced forward transfer of micro - and nano-scale droplets. 5th International Congress on Laser Advanced Materials Processing (LAMP 2009), Kobe, Japan, Kobe, Japan. 28 Jun - 01 Jul 2009.

Abstract

Laser-Induced Forward Transfer (LIFT) [1] of micro- and nano-scale droplets is a relatively well-understood process experimentally [2,3]. By careful control of the applied laser fluence to just melt through a thin source film (the donor), it is possible to transfer single droplets of the film to a receiver substrate placed nearby. Such droplets can be micron [2] or sub-micron [3] in diameter and have potential applications in plasmonic devices. The process is inherently complex involving laser-induced phase changes (which may be non-thermal on femtosecond timescales), droplet growth from fluid flow in thin molten films, moving boundaries, and the flight dynamics of the droplet during transfer and upon impact at the receiver. At present, a complete model that encompasses all these different phenomena is still lacking. However, an approximate numerical model of the process would be highly desirable so that the various experimental parameters (laser fluence, donor thickness, donor-receiver separation etc.) can be optimised for minimum droplets sizes and close deposit spacing. One method of modelling highly complex processes is to use cellular automata [4]. In a cellular automaton, the spatial domain is split into a regular grid of cells whose states evolve in time according to a set of rules based on the states of neighbouring cells. An advantage of this technique for highly complex systems such as the LIFT of droplets is that rules which reproduce the behaviour of a system can be found without explicit derivation from the underlying physical equations.

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Contributors

Author: R.W. Eason

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