Piezopolymer Diaphragm as high performance biosensor platform
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Piezopolymer Diaphragm as high performance biosensor platform Zhimin Li1, Suiqiong Li1, Zhuo Xu2 and Z.-Y. Cheng1 Materials Research and Education Center, Auburn University, Auburn, AL 36849, USA 2 EMRL, Xian Jiaotong University, Xian 710049, China 1
ABSTRACT Piezopolymer PVDF and P(VDF-TrFE) based diaphragms were fabricated. The diaphragm can be used as a high performance sensor platform for using in liquid. The microelectronic process for fabricating microdiaphragm and its array has been established. The performance of the PVDF based diaphragm in air and liquid was tested. It is found that the diaphragm works well in liquid. INTRODUCTION The ability to identify a very small number of target proteins/bacteria in a small volume of sample, mostly liquid, would greatly advance scientific research into the human genome, and provide a more sensitive tool for medical diagnostics. Immunosensors (or biosensors) have great potential for future pathogen detection due to their extreme sensitivity and near real-time detection capability. Much research is currently being conducted on biosensors that utilize microcantilevers (MCs) and other acoustic wave (AW) devices as sensor platforms due to the fact that the AW device as a sensor platform offers the capability for real-time detection; and many other advantages, such as simplicity and low cost [1-3]. For biodetection, the AW device is usually immobilized with a biomolecular recognition layer, such as antibody, on the surface to react with the target species [3,4], which results in a change in the recognition layer, such as the mass. The principle of these AW-based biosensors is based on a fundamental feature of the AW device as a resonator – the resonance frequency of the device changes with the mechanical load. Therefore, the performance of these AW devices is characterized using two parameters: 1) the mass sensitivity (Sm), which describes the shift in resonance frequency due to the attachment of a unit mass onto the surface of the device; 2) the mechanical merit factor (Q value), which defines the sharpness of the resonance peak. The higher Q value means a sharper resonance peak, which would result in a higher precision in determining resonance frequency and a smaller minimum detectable frequency change. Therefore, when developing high performance sensors, the AW devices with higher Sm and Q value are desirable [5-7]. Based on the comparison of different AW devices including quartz microbalances, it has been determined that the MCs provide much higher sensitivity in terms of the minimum detectable mass [5-7]. In other words, the MCs have the capability to detect a much smaller mass attachment. For example, it was demonstrated that an MCs in length about 20 µm are capable of detecting a single E. coli cell [8], and that an MC of 6 µm in length and 160 nm in thickness is capable of detecting a mass in attograms (10-18 gram) [9]. Additionally, the MCs have a compact size. Therefore, it is interesting to employ MCs as sensor platform for developing high performa
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