Superparamagnetic bead assembly via biomolecular recognition and detection using micro Hall sensor*

Specific binding of biological molecules onto a selectively functionalized area is a necessary key step in biological sensing with a solid state device. Here we present our results on the directed self-assembly of streptavidin coated superparamagnetic micron and submicron sized beads onto selectively biotinylated solid-state surfaces with organic molecular templates. Large-scale high-yield assembly of 130nm strepdavidin-coated beads onto biotinylated micro-patterns with little nonspecific binding is realized using molecular template generated by micro-contact printing. Specific binding of similar beads onto a semiconductor micro-Hall cross can be realized using high-spatial registry functionalization with dip-pen nanolithography, and the binding can be detected using phase sensitive Hall magnetometry with InAs quantum well micro-Hall sensors.\footnote{G. Mihajlovi{\ae} et al., APL 87, 112502 (2005).}