Fabrication of Hierarchical Structures by Wetting Porous Templates with Polymer Microspheres
Original entry: William Bonificio, AP 225, Fall 2009
Fabrication of Hierarchical Structures by Wetting Porous Templates with Polymer Microspheres Jiun-Tai Chen, Dian Chen, Thomas P. Russell Langmuir 2009 25 (8), 4331-4335
Soft matter keywords
Polystyrene, microspheres, heirarchical structure, glass transition temperature
The researchers used a very simple method using capillarity to create a hierarchical structure. Polystyrene spheres were first allowed to self assemble over a silicon substrate, this being the first length scale of the structure. After this a nanoporous sheet of aluminum was placed over the top of the spheres. The spheres were then heated above their glass transition temperature. At this point capillary action occurred within the pores on the polystyrene, causing the polystyrene to rise up into the spheres. This created many 'bumps' on the spheres - giving rise to the second length scale of the hierarchical structure.
Soft matter discussion
Two soft matter phenomenons of self assembly and capillarity were utilized by the researchers in this experiement to create their hierarchical structure.
First, a suspension of polystyrene spheres was placed on a clean silicon wafer, and allowed to dry over night. As the suspension dissolved the spheres self assembled into an hexagonal monolayer across the wafer.