RESEARCH PROFILE: Microsized 'giant' drives new rapid-screening device

摘要

Using the same technology that lies at the heart of miniaturized hard drives, researchers at the University of Utah, Iowa State University, and NVE Corp. have developed a high-speed assay system amenable to on-site screening of biological samples. In a pair of papers published in AC (DOI 10.1021/ac8009577; 10.1021/ac800967t), Marc Porter and colleagues demonstrate that the phenomenon known as giant magnetoresistance (GMR) can detect as few as 800 1-(mu)m-diameter magnetic beads bound to a 0.04 mm~(2) spot on an assay chip. "Using what is essentially an exploded hard drive, we've created a device that can ultimately serve as the reader for what we envision to be a 'wellness card', a disposable coupon that would diagnose specific diseases from a drop of saliva or a pinprick of blood," says Porter. Magnetoresistance is the change of resistance in a conductor when it is placed in an external magnetic field. GMR, discovered in 1988 by Albert Fert and Peter Grunberg (who were awarded the 2007 Nobel Prize in Physics for their work), is a supersized response seen in composite materials that are formed from alternating nanometer-thick layers of ferromagnetic and non-magnetic metals. When even a minuscule magnetic field passes over a GMR sensor, the device experiences a disproportionately large change in resistance. Incorporating GMR technology into a disk drive read-write head enables each data bit to be recorded onto and read from a much smaller area than was possible with many older technologies. In a bioanalytical device, GMR-based sensors afford the opportunity to detect a very small amount of an analyte bound to a magnetic bead.