Giant Magnetoresistance Sensors. 1. Internally Calibrated Readout of Scanned Magnetic Arrays

TitleGiant Magnetoresistance Sensors. 1. Internally Calibrated Readout of Scanned Magnetic Arrays
Publication TypeJournal Article
Year of Publication2008
AuthorsNordling J, Millen RL, Bullen HA, Porter MD, Tondra M, Granger MC
Journal TitleAnalytical Chemistry
Volume80
Pages7930-7939
Date Published11/01
Type of ArticleArticle
ISBN Number0003-2700
Accession NumberISI:000260567000009
KeywordsBIOLOGICAL APPLICATIONS, CR, fe, GMR SENSORS, INTERLAYER EXCHANGE, LABELED BIOMOLECULES, layers, MICROBEADS, performance, SPIN-VALVE SENSORS, SUPERPARAMAGNETIC NANOPARTICLES
Abstract

Ibis paper describes efforts aimed at setting the stage for the application of giant magnetoresistance sensor (GMRs) networks as readers for quantification of biolytes selectively captured and then labeled with superparamagnetic particles on a scanned chip-scale array. The novelty and long-range goal of this research draws from the potential development of a card-swipe instrument through which an array of micrometer-sized, magnetically tagged addresses (i.e., a sample stick) can be interrogated in a manner analogous to a credit card reader. This work describes the construction and testing of a first-generation instrument that uses a GMR sensor network to read the response of a "simulated" sample stick. The glass sample stick is composed of 20-nm-thick films of permalloy that have square or rectangular lateral footprints of up to a few hundred micrometers. Experiments were carried out to gain a fundamental understanding of the dependence of the GMR response on the separation between, and planarity of, the scanned sample stick and sensor. Results showed that the complex interplay between these experimentally controllable variables strongly affect the shape and magnitude of the observed signal and, ultimately, the limit of detection. This study also assessed the merits of using on-sample standards as internal references as a facile means to account for small variations in the gap between the sample stick and sensor. These findings were then analyzed to determine various analytical figures of merit (e.g., limit of detection in terms of the amount of magnetizable material on each address) for this readout strategy. An in-depth description of the first-generation test equipment is presented, along with a brief discussion of the potential widespread applicability of the concept.

DOI10.1021/ac8009577
Alternate JournalAnal. Chem.