The Research On Wireless Magnetoelastic Microbiosensor

This dissertation focuses on the magnetoealstic biosensor and its applications in biochemical analysis. In response to a time varying magnetic field, the magnetoelastic sensor efficiently couples and translates magnetic energy to mechanical energy. The elastic energy mechanically deforms the sensor, causing it mechanically vibrate along to its length. If the frequency of the ac field is equal to the mechanical resonance frequency of the sensor, the vibration amplitude is maximum, and the sensor vibrates at its characteristic resonance frequency that shifts in response to mass loading. Since the sensor material is also magnetostrictive, the mechanical oscillation in turn generates a magnetic flux that can be remotely detected using a pick-up coil. The sensor is totally passive. Neither physical connections between the sensor and the detection system are required, nor is any internal power required. The wireless nature of the magnetoelastic sensor makes it a powerful candidate for in situ and in vivo analysis.In this dissertation, three kinds of magnetoelastic biosensors were developed:(1) A wireless magnetoelastic sensor for determination of Escherichia coli O157:H7 (E. coli O157:H7) is developed. The magnetoelastic E. coli sensor was fabricated by coating a layer of functionalized mannose on a magnetostrictive ribbon, which pre-coated with a layer of polyurethane film. The multivalent binding of lectin concanavalin A (Con A) to the E. coli surface O-antigen and mannose favors the strong adhesion of E. coli to the mannose-modified magnetoelastic sensor; E. coli is rigidly and strongly attached on the mannose-modified sensor through Con A, which works as a bridge to bind E. coli to the mannose-modified sensor surface. As E. coli is bound to the sensor, its resonance frequency shifts due to the increasing of the loading mass of sensors, enabling quantification of E. coli concentration with a limit of detection of 60 cells/mL and a linear logarithmic response range of 6.0×101 to 6.1×109 cells/mL. Because of the special recognization between the lectin and bacteria, the sensor can also is used to detecting others gram negative bacteria. The analysis can be directly conducted without incubation and completed in 3 h or less. The proposed magnetoelastic sensor platform offers a great opportunity for developing a useful in vivo and in situ bacteria measurement technology.(2) The coagulation speed of blood was studied applying a wireless magnetoelastic sensor. The effect of microorganisms (E. coli O157:H7, Pseudomonas...