The PDMS is poured (Fig. 1A) on the vertically standing bullet to achieve a complete coverage of the surface, the ratio of the PDMS: reticulating agent and the temperature for the curing have
been tuned for obtaining a homogeneous film.
The latter parameter is the most crucial because a too slow curing would cause the slow
dripping down of the fluid PDMS thus to a thickening of the lower portion and to a final inhomogeneous sample.
The film realized in such a way (Fig. 1B) will then be laid on a glass slide for its morphological characterization.
A possible issue of the PDMS samples is that they can easily adsorb environmental contaminations (powder, micro-hair), thus a further important step consists in sonicating it in 99% ethanol for 5 min.
This treatment does not damage the replica (PDMS is not brittle at all thus sonication is not
eroding it) and promote its good positioning on the underlying support (see Supplementary materials).