Controlling inplane orientation of a monolayer colloidal crystal by meniscus pinning

We demonstrate the usage of meniscus pinning by surface relief boundaries to control in-plane orientation of monolayer colloidal crystals without the interruption of grain disorientation. By optimizing the pinning boundary and withdrawal speed, a well controlled linear meniscus contact line offers unidirectional growth of a colloidal crystal-densely packed crystal direction ⟨11⟩ and ⟨10⟩ parallel to linear edge-giving rise to a single domain crystal with only twins and vacancies present as residual defects. The pinning effect works by eliminating the wavy contact line induced by fingering instability which is commonly found in liquid wetting film. It is found that surfactants and colloidal particles play significant roles to enhance edge pinning, increasing the distance traveled by receding bulk meniscus (during substrate withdrawal) before liquid depinning or rupturing.