We have investigated a new magnetic labelling technology for high-throughput biomolecular identification and DNA sequencing. Planar multi-bit magnetic tags comprising a magnetic barcode formed by an ensemble of micron-sized thin film ferromagnetic Co bars and a 15 x 15 micron Au square for immobilization of probe molecules have been designed and fabricated. We show that by using a globally applied magnetic field and magneto-optical Kerr microscopy the magnetic elements in the multi-bit magnetic tags can be addressed individually and encoded/decoded remotely. The power of the approach is the read/write technique, which allows modest globally applied magnetic fields to write almost unlimited numbers of codes to populations of tags rather than individuals. The magnetic nature of the technology also lends itself naturally to fast, remote decoding and the ability to rewrite tags if needed. We demonstrate the critical steps needed to show the feasibility of this technology, including fabrication, remote writing and reading, and successful functionalization of the tags as verified by fluorescence detection. This approach is ideal for encoding information on tags in microfluidic flow or suspension, in order to label oligonucleotides during split-and-mix synthesis, and for combinatorial library-based high-throughput multiplexed bioassays.

We report a new magnetic labelling technology for high-throughput biomolecular identification and DNA sequencing. Planar multi-bit magnetic tags have been designed and fabricated, which comprise a magnetic barcode formed by an ensemble of micron-sized thin film Ni 80 Fe 20 bars encapsulated in SU8. We show that by using a globally applied magnetic field and magneto-optical Kerr microscopy the magnetic elements in the multi-bit magnetic tags can be addressed individually and encoded/decoded remotely. The critical steps needed to show the feasibility of this technology are demonstrated, including fabrication, flow transport, remote writing and reading, and successful functionalization of the tags as verified by fluorescence detection. This approach is ideal for encoding information on tags in microfluidic flow or suspension, for such applications as labelling of chemical precursors during drug synthesis and combinatorial library-based high-throughput multiplexed bioassays.

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The influence of submonolayer quantities of O and N adsorbed on ultrathin Co∕Cu(001) films as a function of Co thickness has been studied using spin polarized secondary electron spectroscopy. The gaseous adsorbate was prepared by depositing Co on (2×22)R45°-O and c(2×2)-N reconstructed Cu(001) utilizing surfactant effects to reproducibly control quantity. Adsorbed quantities were monitored by Auger electron spectroscopy and surface reconstructions by low energy electron diffraction. The secondary electron spin polarization increases with the Co film thickness, following an exponential law, and the chemical interaction between the adsorbate and the Co reduces polarization to (98±2)% in the case of O and (84±3)% in the case of N compared to the uncovered substrate. For both, the onset of ferromagnetism is suppressed by approximately 1 ML. The effects on polarization and the onset of ferromagnetism are attributed to the partial cancellation of the magnetic moment in the Co layer adjacent to the adsorbate. The estimated reduction in moment is comparable to the results of theoretical predictions.

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