Facile Wettability-Patterned Flexible Surface for Multifunctional Microdroplet Array Manipulation

Droplet array guided by wettability patterns has attracted extensive interest due to its applications ranging from multiplex bioassay to cell screening. This paper reports a facile fabrication method for a wettability patterned flexible surface to effectively generate and manipulate droplet array. Elastomeric PDMS is prepared followed by soft lithography, chemical vapor deposition, and plasma treatment. Various patterns, i.e., dots, lines, and letters, are successfully demonstrated with kinds of masked plasma exposure. Due to the fully wetted Wenzel state, the patterned surface can stick the water droplet even when bending and twisting. Droplets can also be transported directly from one to the other to perform mixing and sensing, and a proof-of-concept visualized colorimetric detection of starch was successfully demonstrated. It is expected that such facile wettability patterned flexible surfaces are promising in smart droplet-based assays.