A simple and novel method is firstly reported for controlling coffee ring structure on polystyrene(PS)film surface by O_2 plasma. O_2 plasma treatment leads to the wettability change of PS surface from hydrophobic to hydrophilic. For hydrophilic PS surface the coffee ring structure is avoided relying on the motion of contact line(CL) while SiO_2 microspheres are left. The motion of the CL is produced based on the viscosity and Marangoni effect with the addition of polymer additives. For hydrophobic PS surface coffee ring structure still persists even with polymer additives because SiO_2 microspheres transfer with the motion of the CL at the beginning of droplet evaporation and accumulate at the droplet edge at late stage with the pinning of the CL. As a result, uniform and macroscale SiO_2 microspheres deposition without coffee ring structure and SiO_2 microspheres deposition with coffee ring structure are controlled by O_2 plasma. This method provides a new way to tune coffee ring structure with smart surface and may be potentially useful for a range of application at material deposition and diagnosing diseases.
Li-Ying CuiYu YanXin-Yu ZhaoCun-Long YuYing MaBai Yang
With the development of science and technology,ordered microstructures with special functions have aroused intense research interest.These functional microstructures have been widely used in fields of microelectronic devices,micro-reactors,biochemical sensors and optical devices,etc.This paper summaries our work on preparation and application of microscopic patterned surfaces with ordered microstructures,and looks into the future development of this field.
