Simple route to ridge optical waveguide fabricated via controlled evaporative self-assembly

Because of increased interest in the development of integrated hybrid optoelectronic devices for use in photonic sensors and communication services, new methods for device fabrication by utilizing simple, fast and inexpensive process are highly desirable. In this regard, drying-mediated self-assembly of non-volatile solutes (polymers, nanocrystals, nanoparticles, nanorods and DNA) through irreversible solvent evaporation has received considerable attention for its ease of producing complex, largescale structures in one-step for potential applications in microelectronics, optoelectronics and biotechnology. Recently, it has been demonstrated that highly organized structures with controlled size and shapes over large areas can be achieved by precisely regulating the solvent evaporation process in a restricted geometry composed of a curved surface situated on a flat substrate (curveon-flat geometry). The repetitive ‘‘stick–slip’’ motion (i.e., pinning–depinning) of a three-phase contact line of the evaporating drop was effectively controlled in such a restricted geometry, forming well-ordered coffee ring-like deposits. Notably, by rationally designing the upper curved surface of the restricted geometry to accommodate different shapes, more intriguing and complex patterns can be readily created. Such regularly organized, complex structures can be considered as device-oriented structures and may potentially be integrated into microelectronic, optical, optoelectronic, and sensing devices.