Mechanics of Magnetoelastic MEMS Sensors for Bio-Detection

ABSTRACT: Ferromagnetic materials have shown to possess some unique and useful properties, one of which is that they are magnetomechanical transducers, that is, they exhibit a change in dimension when they are subjected to an external magnetic field and vice versa. This work details the development of a magnetoelastic sensor for the detection of biological species via frequency shift by mass addition. Meso and microscale resonators were fabricated and driven to longitudinal mode resonance by a modulated magnetic field. Finite element analysis was performed to simulate spore/cell attachment and the frequency shifts were found to be sensitive to the location of the mass on the surface with sensitivity increasing towards the free ends. These results were verified by numerical studies and followed by experiments demonstrating the sensor’s ability to detect the presence of Bacillus anthracis Sterne strain spores. INTRODUCTION: The study of mass-based acoustic wave sensors has been a major focus of researchers devising chemical and biological detectors [1-5]. The principle of detection in these sensors involves measuring a resonant frequency shift as the target species attaches to the sensor, effectively this mass addition of mass dampens the resonant behavior of the sensor platform. Prior work by several researchers [6-15] and the authors [16-18] have focused on a novel acoustic sensor fashioned from magnetostrictive materials in the form of a simpl