Jet-on-jet ejection phenomena during laser-induced forward transfer (LIFT) of silver nanoparticle inksThursday (25.06.2020) 16:20 - 16:40 Room 1
In the field of printed electronics well known and established material deposition techniques, like screen printing, inkjet or dispensing are being pushed to their limits. These technologies could be substituted by laser-based material deposition methods, such as laser-induced forward transfer (LIFT), which can offer high throughput, more flexibility and deposition sizes down to 10 µm . One of the main reasons of LIFT drawing a lot of attention from research and industry is its applicability to a wide range of materials, including pure metals, polymers, ceramics, semiconductors and even biomaterials . LIFT printing of complex materials, like silver nanoparticle inks is not an exception. However, clean and well controlled printing of these non-Newtonian inks requires a careful selection of the processing parameters as well as understanding the physical phenomena of the ejection mechanism [2,3]. Time-resolved shadowgraphy imaging is the most widely used tool for investigation of the LIFT ejection dynamics, which had revealed that the growth and collapse of a laser-induced cavitation bubble is responsible for the liquid material ejection [4,5]. Typically, a single, relatively large jet of donor material is ejected by a single laser pulse. In this study we present and discuss a jet-on-jet ejection phenomenon , where a small(er) secondary jet is ejected super-imposed on a primary large(r) jet, by a single laser pulse, see Figure 1a. Our experimental study employs time-resolved shadowgraphy imaging, detection of the laser-induced plasma emission, optical and confocal microscopy in order to explain the physical phenomena driving this jet-on-jet formation. It was found that two main parameters playing the main role in this effect are the laser spot diameter at the donor surface and the laser fluence level. At high(er) fluence levels, laser-induced plasma and shock wave occur at the donor surface, which are responsible for the small(er) secondary jet generation, see Figure 1b. If the fluence level is further increased, the laser-induced plasma and shock wave forms a crater in the carrier surface.
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