Schematic illustrations of the CULP process.
(a) A mixed solid film, consisting of a gas medium (light)
and an intended material (dark) is condensed on the substrate
at low temperature. (b) At higher pressure and temperature,
this film goes into the liquid phase and nano-particles are assembled.
(c) When the nanoparticles are strongly bonded to the substrate,
compared with the surface tension, partial drying of the liquid
has little effect on the positioning of the nanoparticles.
(d) When the surface tension is large,
the nanoparticles may be swept by the liquid droplets.