RESEARCH
 

Directed Wetting, Adhesion and Assembly on Topographically Structured Polymer Surfaces

Control of interfacial properties, such as wettability, adhesion, friction, and biocompatibility, is of great importance for both fundamental science and practical applications, including microfluidics, micro- and nanofabrication of complex structures, crystal formation, and cell attachment. One of the major challenges is how to spatially control the molecular recognition in different regions of surface and interface. It is well known surface properties can be manipulated by both physical roughness (topography) and chemical heterogeneity. Superhydrophocity found in Lotus leaves and insect wings has been attributed to their micro- and nano-rough topology. Biomechanics researchers, on the other hand, show that the gecko's toe pads have millions of nanopillars on tips of micropillars, which allow gecko to cling a wide variety of substrates while the pads remain clean.

Inspired by the unique natural design, we are interested in developing novel synthetic approaches and fabrication strategies to selectively graft adaptive polymer brushes at specific locations on topographic polymer substrates, including high-aspect-ratio pillars, and various 2D and 3D microporous structures. We will fine-tune the brush chemistry, grafting strategy, grafting density, polymer brush (relative) chain length, chemical nature, composition, and architecture. We aim to establish quantitative understandings of the microscopic nature of the wetting behaviors as a function of dual roughness, wetting transition between different wetting and nonwetting states, in particular, the degree of liquid penetration in the nanostructured layer.

Directed Wetting

 

Further readings:

Lin, P., Vajpayee, S., Jagota, A.*, Hui, C.-H., and Yang, S.*, “Mechanically Tunable Dry Adhesive from Wrinkled Elastomers”, Soft Matter, 2008, 4 , 1830 - 1835. DOI

Chandra, D., Taylor , J. A. and Yang, S.*, “Replica molding of high-aspect-ratio (sub-)micron hydrogel pillar arrays and their stability in air and solvents”, Soft Matter, 2008, 4 , 979-984. DOI.

Zhang, Y., Qin, S. Taylor , J. A., Aizenberg, J. and Yang, S. “Selective Wetting and Adhesion on Micropillar Arrays Grafted with Thermoresponsive Polymer Brushes”, Proc. ACS Div. Polym. Chem ., 2007 , 48 (1) , 256-257.

Zhang, Y. †, Lo, C.-W. †, Taylor , J. A. and Yang, S.*, “Replica molding Replica Molding of high-aspect-ratio nanopillar arrays with high fidelity”, ( †: equal contribution), Langmuir, 2006, 22, 8595. DOI.

Krupenkin, T. N.; Taylor, J.A.; Schneider, T. M.; Yang, S. “From Rolling Ball to Complete Wetting on Dynamically Tunable Nanostructured Surfaces”, Langmuir , 2004 , 20 , 3824 (cover of the month). DOI.