Novel Multibit Magnetic Tagging Techniques for High-Throughput Multiplexed Chemical Analysis

In this paper, we have investigated a remote encoding/decoding method of micrometer-sized multibit magnetic tags and demonstrated the operation of magnetic digital tags to discuss the practical issues which arise. The tags are formed from micron scale patterned ferromagnetic Co thin films, which are engineered to have different switching fields by tailoring the geometric shape of the elements. This enables the tags to be encoded and read by a sequence of globally applied magnetic fields. Full-field magneto-optical microscopy was used to achieve the remote writing and reading for magnetic digital tags. Our results demonstrate that the elements in the multibit tags are well separated in switching field and can be encoded/decoded independently by using globally applied magnetic fields and magneto-optical microscopy. We will discuss practical issues for high-information multibit magnetic tags including switching field distribution and repeatability with implications for the field of bioassays.