Figure 5
The coalescence of ink droplets allows the formation of a nearly uniform surface on a flat substrate with a thickness deviation of no more than 20–30 nm along the Z axis.
In the experiments, droplets of titania sol with varied volumes (2, 5, and 10 pL) were deposited on the glass surface. The drop size was differentiated by changing the grayscale brightness of pixels. Here we use optimal ink solution with 30 vol. % of the stock TiO2 sol with surface tension 23.0 ± 0.4 mN/m and viscosity of 3.2 ± 0.2 mPa⋅s. The drop-on-demand inkjet printing (DOD) with room-temperature drying allows to create three stages of drop-on-surface interaction–single drops, coalescence and line formation. The resulting structures were characterized by optical microscopy (a) and atomic force microscopy (AFM, b). AFM provides information about the cross-section (c) of border effects and places of interaction between drops from which the roughness of the surfaces can be assessed.
