KEYWORDS: Sensors, Magnetic sensors, Magnetism, Resistance, Nondestructive evaluation, Solar concentrators, Signal to noise ratio, Signal processing, Aluminum, Thin films
New high-sensitivity solid-state magnetoresistive (MR) sensor technologies offer significant advantages in nondestructive evaluation (NDE) systems. A key advantage of MR sensors is a flat frequency response extending from dc to hundreds of MHz, making them particularly attractive for low-frequency and multi-frequency eddy current detection for deep-flaw detection and depth profiling. MR sensors are mass produced by thin film processing techniques similar to integrated circuit manufacturing, dramatically reducing the cost per sensor. The fabrication process is compatible with silicon circuit technology, allowing integration of sensors with on-chip signal processing. MR sensors can easily be produced in dense arrays for rapid, single-pass scanning of large areas. The small size and low power consumption of these solid-state magnetic sensors enable the assembly of compact arrays of sensors on a variety of substrates as well as on-chip sensor arrays. Arrays have been fabricated with sensor spacing as small as 5 μm. This paper presents a review of the state of the art in MR sensors and applications in NDE. The physical principles, manufacturing process, and performance characteristics of the three main types of MR devices, anisotropic magnetoresistance (AMR), giant magnetoresistance (GMR) and tunneling magnetoresistance (TMR) are discussed. Their performance is compared to other magnetic sensor technologies for NDE applications. Finally, we provide a comprehensive review of the literature on NDE applications of MR sensors.
Spintronics detection technology can add significant functionality to bioassay detection systems and improve their precision. Photonic detection is presently the dominant technology in bioassay systems. Optical detectors on mechanical scanners are used to read the vast majority of commercially produced DNA chips. Introduction of these optical systems into non-laboratory applications is greatly impeded by the cost, size, and complexity of optical systems. Magnetics can help by providing detectors and actuators that are inherently rugged, small, and mass-manufacturable. Magnetic nanoparticles are used in many biochemical assays as labels for concentration, manipulation and, more recently, detection. Typically one attaches the magnetic particles to the biochemical species of interest (target) using a chemically specific binding interaction. Once bound, the labels enable the manipulation of the target species through the application of magnetic forces. Spintronic sensors, specifically Giant Magnetoresistive (GMR) and Spin Dependent Tunneling (SDT), sensors have been developed to detect and quantify labels in two main formats: flowing in a microfluidic channel, and immobilized labels on a chip surface.
Conference Committee Involvement (4)
Smart Sensor Phenomena, Technology, Networks, and Systems II
9 March 2009 | San Diego, California, United States
Sensor Systems and Networks: Phenomena, Technology and Applications for NDE and Health Monitoring
19 March 2007 | San Diego, California, United States
Advanced Sensor Technologies for NDE and Structural Health Monitoring II
1 March 2006 | San Diego, CA, United States
Advanced Sensor Technologies for Nondestructive Evaluation and Structural Health Monitoring
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