In this paper, results of an investigation on the process of drop formation in piezo‐electrically driven drop‐on‐demand inkjet systems are presented. The focus is on theoretical hydrodynamical aspects of the process with special attention to drop constriction. It is shown that the inception of drop constriction has its origin in acceleration forces in contrast to the well‐known phenomena in the field of interfacial instability such as pendant drop, end pinching and capillary wave break‐up. Some results from computer simulations and from experimental investigations are also added to illustrate relevant processes preceding and following drop constriction.

Large areas of regular diffraction nanogratings were produced consisting of so-called laser-induced periodic surface structures (LIPSS) on thin molybdenum layers ($<400nm$) deposited on a borosilicate glass substrate. The aim was to produce these structures without ablating nor cracking the molybdenum layer. Ultra short laser pulses were applied using a focused Gaussian beam profile. Processing parameters such as laser fluence, pulse overlap, number of overscans, repetition frequency, wavelength and polarization were varied to study the effect on periodicity, height, and especially regularity of the obtained LIPSS. It was found that a careful choice of the correct laser parameters is required to avoid detrimental mechanical stresses, cracking, and delamination during the laser processing of the layer in order to remain in its correct range of ductility as well as to ensure regular LIPSS. A possible photovoltaic application of these nanogratings could be found in texturing of thin film cells to enhance light trapping mechanisms.