Design and Performance of GMR Sensors for the Detection of Magnetic Microbeads in Biosensors
NAVAL RESEARCH LAB WASHINGTON DC
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We are developing a biosensor system, the Bead ARray Counter BARC, based on the capture and detection of micron-sized, paramagnetic beads on a chip containing an array of giant magnetoresistive GMR sensors. Here we describe the design and performance of our current chip with 64 sensor zones, compare its performance with the previous chip design, and discuss a simple analytical model of the sensor micromagnetics. With assay-ready Dynal M-280 microbeads 2.8 m diameter, our threshold for detection is approximately 10 beads per 200 m-diameter sensor. Single beads made of solid Ni30Fe70 can easily be detected, but they must be made biocompatible. The relatively large size of our sensors helps to improve their practical sensitivity compared with other microsensor-based magnetic particle detectors.
- Electricity and Magnetism