Numerical simulation of the deposition of a liquid thread on a moving substrate. The influence of the geometrical parameters

SEBASTIÁN UBAL; PAUL GRASSIA

Glasgow, Reino Unido

Congreso; European Congress on Advanced Materials and Processes (EUROMAT 2009); 2009

Direct write is a term involving a number of technological processes characterized in general by the localized (through an acute nozzle, tip, probe) delivery of material, energy, etc. to a given substrate. In particular, in printed electronics applications, the direct writing of conducting tracks and functional components becomes a convenient alternative to conventional techniques for non­-flat substrates, enabling a faster development and greater production flexibility.This work analyzes the deposition of a liquid being dispensed downwardly from a nozzle. A horizontal substrate, located closely below, moves at a constant relative velocity along its own plane. Hence, the fluid impinging the moving plate is being deposited and dragged, leaving behind the nozzle a fluid track.We study the process by means of a theoretical model assuming the liquid being Newtonian and the surface tension being constant. We also consider that the contact angle is constant and we remove the singularity at the moving contact line employing Navier´s slip condition. The resulting model is solved numerically by means of the Finite Element Method combined with an Arbitrary Lagrangian Eulerian Technique, both implemented within the commercial software COMSOL Multiphysics.The deposition process is characterized by nozzle­-based and substrate­-based capillary numbers (Can=mU/s, Cas=mV/s; m: liquid viscosity, s: surface tension, V: substrate relative speed, U: mean inlet velocity), the Laplace number (La=rsR/m2; r: liquid density, R: nozzle radius), the Bond number (Bo=rgR2/s), the contact angle and several geometrical parameters, including the ratio between the nozzle­-substrate distance and the nozzle diameter.We conducted both transient and steady state numerical experiments aimed to determine the influence of the geometrical parameters on the deposition process.