Magnetically labelled gold and epoxy bi-functional microcarriers for suspension based bioassay technologies

Microarrays and suspension-based assay technologies have attracted significant interest over the past decade with applications ranging from medical diagnostics to high throughput molecular biology. The throughput and sensitivity of a microarray will always be limited by the array density and slow reaction kinetics. Suspension (or bead) based technologies offer a conceptually different approach, improving detection by substituting a fixed plane of operation with many individually distinguishable microcarriers. In addition to all the features of a suspension based assay technology, our technology offers a rewritable label. This has the potential to be truly revolutionary by opening up the possibility of generating, on chip, extensive labelled molecular libraries. We unveil our latest SU-8 microcarrier design with embedded magnetic films that can be utilized for both magnetic and optical labelling. The novel design significantly simplifies fabrication and additionally incorporates a gold cap to provide a dual surface, bi-functional architecture. The microcarriers are fabricated using deep-ultraviolet lithography techniques and metallic thin film growth by evaporation. The bi-functional properties of the microcarriers will allow us to use each microcarrier as its own positive control thereby increasing the reliability of our technology. Here we present details of the design, fabrication, magnetic detection and functionalization of these microcarriers.