Pulse Excitation Method for Magnetoelastic Biosensors

Magnetoelastic (ME) biosensors are being investigated to detect and monitor the presence of foodborne pathogens that may contaminate our foods between the farm and the table. ME biosensors are based upon free-standing, vibrating platforms that change their resonant frequency in response to the capture and accumulation of target pathogens upon the sensor surfaces. The sensor platform is caused to vibrate by an external magnetic excitation field. A common excitation method is to sweep the magnetic field across a range of frequencies that are expected to include the resonant frequency of the sensor. This requires that one know beforehand the resonant frequency and the anticipated frequency shift caused by the capture of the target species, or search for these during measurement. In this work, an alternative (pulse) excitation method has been investigated to measure the resonant frequency of ME biosensors. A pulsed magnetic field was used to excite ME sensors to vibrate with a damped oscillation that decays rapidly. The resonant frequency is determined from the sensor response to the pulse excitation. The performance of a system designed to excite and measure the resonant frequencies of ME biosensors is described and its performance characterized. The operation of the system is demonstrated through the detection of Salmonella on fresh produce.