In situ assembly of colloidal particles into miniaturized biosensors

We show how to create arrays of biosensors by in situ assembly of colloidal particles onto micropatterned electrodes. Latex microspheres from suspension are collected via dielectrophoresis in the micrometer-sized gaps between planar electrodes. The assembled particulate patches are fixed by changing the colloidal interactions to induce coagulation. Immune-active sites on the latex surfaces bind the target molecules. A direct electric conductivity readout is accomplished after secondary tagging with colloidal gold and its enhancement by silver nucleation. The method holds promise for creating disposable on-chip arrays of highly sensitive miniature sensors for specific proteins, DNA fragments, or other biomolecules.