Topography measurements are suitable for samples of microlevel roughness (1-60um level roughness can be analysed). In addition, it is required that the samples are diffusive, in other words not transparent. Sample height is limited to 22 mm.
The minimum and maximum droplet size depends on both the liquid and needle type used, as well as of the substrate. The table below shows estimates for water. All the volumes are droplets hanging on the needle (except picoliter dispenser). This is because the amount of liquid actually transferred from the needle to the substrate depends on the surface. If the substrate is very hydrophilic, more liquid is transferred and if it is very hydrophobic the amount of liquid on the surface can be less than in the needle. Please notice the values are approximate and depend on the measurement system and environment.