Approaches to Generating Selectivity in Microcantilever Sensors

Microcantilever (MC) sensors have emerged as sensing transducers that offer greater sensitivity than comparable sensors due in large part to their very small dimensions. MCs have been utilized in many chemical sensing applications. Not only do MCs demonstrate greater sensitivity, but they also are relatively low in cost, they can be used in an array format, and they can be integrated into on-chip electronic circuitry.

While MC sensors demonstrate great sensitivity, an area of weakness that MC sensors must overcome is that of selectivity. The response of a MC sensor to analyte is mechanical; these mechanical responses lack the information rich spectral features like those found in vibrational spectroscopic techniques. Thus the underlying goal of this research is to develop approaches to enhancing selectivity in MC sensors.

The initial research focused simply on demonstrating that MC sensors could be functionalized with thiolated self-assembled monolayers (SAMs) and then used to detect metal ions in the liquid phase. The initial research not only demonstrated the moderate selectivity of SAMs to metal ions, but also the good sensitivity at which these metal ions could be detected.

The second phase of the research represented the first time that microcantilever array sensors (MCAs) were functionalized with SAMs having different ligand functionalities on one sensor chip. The MCA was exposed to different metal ions and the response signatures used in conjunction with pattern recognition algorithms to identify and quantitate the metal ion injected.

In an extension of the metal ion array research, the SAM MCA was coupled to an ion-exchange chromatography (IEC) column for the separation and detection of metal ions.

The second major division of research presented in this work involves improving the selectivity of detection of analytes in the gas phase. MCAs differentially coated with polymeric RPs by way of PVD were made. Experimental parameters were adjusted to determine if the parameters would impact the selectivity of the MCA.

The final project involved taking the former gas phase project a step further by invoking the use of gas chromatography (GC) to impart selectivity to the system.