  The evaporation of a droplet induces variety of ordered patterns near the
contact line between the droplet and a substrate. This pattern formation
involves both the behavior of colloidal suspensions and interactions between a
droplet and a substrate. Although studies on the effect of the behavior of
colloidal suspensions on the deposition process have been actively conducted,
studies on the effect of the interaction between a droplet and a substrate have
not been actively conducted because the observation of the interaction is
difficult owing to the lack of structural changes in the substrate by the
interaction. In this study, we investigated the solvent-substrate interactions
by using a water droplet and liquid crystals as a substrate, where the liquid
crystals were placed on a glass slide. The orientation patterns of the liquid
crystals were induced at the contact line between the water droplet and the
liquid crystal and were observed using a polarized optical microscope. Pinning
and depinning events were observed at a certain anchoring strength of the
liquid crystal on the glass slide and formed linear patterns on the surface of
the liquid crystal. Additionally, the interfacial tension between the water and
liquid crystal slowly varied at this anchoring strength owing to the variation
in the orientation of the liquid crystals. These results indicated that the
evaporation-induced patterns appeared when the strength of the
solvent-substrate interactions was neutral. The interaction between a droplet
and a substrate is important for the fabrication of desired ordered patterns.
