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
A series of double-hydrophilic double-grafted PMA-g-PEG/PDMA copolymers, which contained poly(methacrylate) (PMA) as backbone, poly(ethylene glycol) (PEG) and poly(N,N-dimethylacrylamide) (PDMA) as side chains synthesized successfully by using reversible addition-fragmentation chain transfer (RAFT) polymerization and atom transfer radical polymerization (ATRP), were used as physical coatings for the evaluation of protein-resistant properties by capillary electrophoresis (CE). Electroosmotic flow (EOF) measurement results showed that the PMA-g-PEG/PDMA copolymer coated capillaries could suppress electroosmotic mobility in a wide pH range (pH = 2.8 9.8) and EOF mobility decreased with the increase of copolymer molecular mass and PDMA content. At the same time, protein recovery, theoretical plate number of separation and repeatability of migration time demonstrated that antifouling efficiency was improved with the increase of molecular mass and PEG content.
Lin TanJin-xing XingFu-hu CaoLi-juan ChenChong ZhangRong-hua Shi王延梅
