Micro-Stain Patterning

Micro-fluidic devices for high-throughput drug screening, proteomics and genomics could often benefit from high-density storage of the reagents. One possible storage device is a matrix of micro-size protein/reagent stains on a substrate that can be easily dissolved and retrieved by an automated micro-pipette system. Such a high-density protein library requires the generation of symmetric and precisely located stains by evaporating micro- and nano-liter drops. We have studied the fundamental mechanisms behind stain patterns left behind by drops of protein, salt and polymer solutions. It is found that the first ring of crystal/precipitate typically forms at the contact line due to enhanced evaporation rate and unfavorable thermodynamics. The crystal patterns that form inwards then depend on the wettability of the substrate, the thickness of the internal film and the height of the first crystal ring. We find diffusion-limiting fractal patterns, cratered mounds, isolated pyramids and a new dramatic annular ring pattern due to a capillary wetting effects near the first ring.

Representative Publication: [145]