Resonance behavior of metallic glass resonators and their application as sensor platform
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Resonance behavior of metallic glass resonators and their application as sensor platform K.W. Zhang, L.L. Fu, S.Q. Li, and Z.-Y. Cheng* Materials Research and Education Center, Auburn University, Auburn, AL36849, USA Utilizing magnetostrictive effect, the metallic glass is used to form mechanical resonators with different configurations. The resonance behaviors of these resonators are studied under different conditions, including different dc magnetic bias fields and different ac magnetic driving field. It is found that the resonators made of metallic glass exhibit a higher quality merit factor. Based on the results, it is also found that the acoustic wave velocity of the metallic glass decreases with increasing frequency. The application of these resonators as sensor platform is investigated. It is found that both odd and even vibration modes can be detected. Therefore, it provides a unique device that is capable to detect the target species on the sensor surface without “blind point(s)”, which is a challenge for all sensors based on other types of resonators. For the biosensors based on these resonators, a high sensitivity was observed. The advantages of these sensors over the current devices are demonstrated by the detection of Salmonella typhimurium (S. typhimurium) in water. INTRODUCTION Acoustic wave (AW) devices has attracted an increasing interest for the development of high performance biosensor due to the facts that the AW devices as biosensor platform have many advantages, such as high sensitivity, easy operation, and cost efficiency. For the development of biosensors, AW devices are used as sensor platform, which is based on the principle that the resonance frequency of the AW device changes with the mass load on the surface of the AW device. That is, the AW devices are actually used as a mass sensor. Therefore, there are two parameters used to characterize the performances of AW devices: mass sensitivity (Sm) and quality merit factor (Q value) [1]. The Sm is defined as the change in resonance frequency per unit mass load. In general, the smaller is an AW device, the higher is its Sm. The Q value reflects the sharpness of the resonance peak. A higher Q value means a shaper resonance peak, which results in a higher accurate in the determination of the resonance frequency. Therefore, an AW sensor with a higher Sm and a larger Q value is highly desirable. In the last decade, much effort has been put on minimizing AW devices, such as micro-cantilevers (MCs) to achieve higher sensitivity. However, the performance of these micro/nano-sensors is challenged by the applications, in which the sensors are mostly required to be operated in liquid environment. Unfortunately, a strong damping effect due to the liquid environment results in a very small Q value. Additionally, all the AW devices have a so-called “blind point” issues due to the node point in the AW device. That is, if the mass load is attached to the node point, the AW device would not be able to detect it. This is especially critical if an AW sensor is
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