Laser-induced forward transfer of low viscosity inks

Laser-induced forward transfer (LIFT) is a laser-based printing technique which has been revealed as an interesting alternative to inkjet printing for the deposition of inks in direct writing applications. The principle of operation of the technique relies on the focusing of a laser beam on a thin film of the ink and the release of a tiny fraction of material through the action of a laser pulse, being usually assumed that such pulse should be very short, of the order of ns and below. However, with the aim of reducing production costs it would be desirable to operate with longer pulses (hundreds of ns and above), so that less expensive lasers could be employed. In this work we prove that it is feasible to carry out the LIFT of liquids with relatively long laser pulses (a few hundreds of ns). To that aim we have investigated the influence of laser fluence on the printed droplets and identified an evolution of their morphology with that parameter somewhat different from the one characteristic of the LIFT of liquids with much shorter pulses. A further time-resolved imaging study has revealed the onset of up to three different transfer mechanisms which correlate well with the deposition outcomes. (C) 2016 Elsevier B.V. All rights reserved.