Fig. 2: Parametric studies showing the capabilities of drop-impact printing technique.

The extent of viscous liquid and low surface tension liquid printing was explored using glycerol water solution, polyethylene glycol (PEG) water solution, and ethanol-water solution. The ejected droplet diameter was plotted with (a) liquid viscosity and (b) liquid surface tension for a sieve with different pore openings. c The printable regime was observed in the plot between Ohnesorge and Reynolds number. The light-blue shaded part shows the printable region of drop-impact printing technique. The range gives us an idea of the extent of different liquids that can be used for printing. d The broad range of liquids is shown in terms of Z number with inset images showing the different liquid drops that can be printed. The drop-impact printing technique (shown with purple color bar) was compared to inkjet printing, electrohydrodynamic (EHD) printing and acoustophoretic printing represented with turquoise, blue, and yellow bars, respectively (scale bar: 100 µm). e The mechanism of different ejection modes was explained based on a timescale factor with varying Ohnesorge number. The critical Ohnesorge number that ensures transition from the inertial to viscous regime was 0.03, and the time- scale factor value that defines the transition from collapse-penetration mode (CPM) to impact-penetration mode (IPM) was found to be 0.04.