(449b) Convective Deposition of Binary Suspensions

We investigate the coupling between the suspension properties and the deposition process during convective deposition of aqueous binary suspensions of colloidal microspheres and nanoparticles. The microsphere monolayer structures formed from this rapid and scalable process have use in a variety of optical, chemical, and biochemical sensing applications. Under ideal conditions, co-deposition of two monosized species creates long range order of the larger species embedded within the nanoparticles when the size ratio of particles is sufficiently large. However, when altering the volume fractions of the two species, instabilities arise that lead to modulation of surface morphology and localized order. At the highest concentration of nanoparticles, the larger species is destabilized via depletion interactions that also strongly interfere with the deposition process through agglomeration and altering the particle-substrate affinity. Direct measurements of deposition are visualized via high speed confocal laser scanning microscopy to generate local dynamic information regarding the deposition as well as the long range structure of assembled microsphere coatings.