Controlled fabrication of macroscopic mesostructured silica spheres for potential diagnostics and sensing applications

We report on fabricating macro-scale mesostructured silica spheres on superhydrophobic surfaces from silica nanoparticles via evaporative self-assembly. The problem of cracking and shattering of the dried macro-spheres has been addressed by using dopants such as graphite, porphyrins and rhodamine-B as well as increasing the evaporation time by using anti-freeze. Limits in size reduction associated with hand-held deposition are overcome using ink-jet deposition - spheres <; 100 μm are routinely produced. Silica spheres doped with porphyrin and fluorescent dyes demonstrate an ability of functionalising these spheres to improve biocompatibility and allow fluorescent diagnostics.