MEMS Biochem Sensors

Research Interests

Micromechanical cantilevers are a new and rapidly developing type of sensor. One of the applications of microcantilevers is to detect small quantities of biochemical molecules by mechanical deflection of a cantilever upon binding to its gold coated and chemically functionalized surface.

The design, fabrication, and implementation of sensors is of great importance to both fundamental research (sensors-as-tools) and clinical research (sensors-as-diagnostic platforms). Microcantilever-based sensors have attracted considerable attention as a label-free approach for detecting chemical and biomolecular reactions via deflection sensing. A major aspect of our research program involves understanding the origin of the signal, allowing optimization of the sensor signal, its reproducibility and stability as well as understanding the maximum signals achievable. We have determined the effect of molecular conformation on measured stress and found that stress is dominated by charge transfer effects into the metal surface by performing a simultaneous electrochemical-stress measurement, providing a direct conceptual link to molecular electronics. These studies also lay the foundation to exploit stress sensing for competitive biochemical sensing. These experiments are performed in close collaboration with electrochemists (Prof. R.B. Lennox, Chemistry McGill) and researchers from the Genome Innovation Center located at McGill (Prof. R. Sladek). Funding provided by the NSERC-CREATE Training Program in Integrated Sensor Systems.

We have built cantilever based sensor systems operating in gas, liquid and full electrochemical controlled environments. The latter has the advantage of allowing in-situ cleaning and characterization of the sensor receptor surface. In addition, it provides for an extra ‘control button’ to change experimental conditions and can be used to perform actuator (in contrast to sensor) experiments. With these systems we investigate the stress evolution during alkanethiol self-assembly and discovered Au(111) grain size dependent kinetic trapping of the lying down phase. This observation could explain the many quantitative discrepancies in measurements of properties of alkanethiols founding the literature. We have furthermore investigated the aging of polypyrrole actuators used as ‘artificial’ muscles and found delamination to be a major failure mechanism. Finally, we have increased the surface stress due to hybridization of complementary DNA strands by a factor of 10-100 as compared to the literature. This allows us to potentially build powerful DNA and other biomolecular sensors as well as investigate the noise and kinetic limits of established gene chip technologies.