A parametric design study of an electrochemical sensor

Abstract

Biological systems contain a multitude of molecules with specific functions and three-dimensional shapes that enable them to selectively interact with other molecules in a coordinated fashion. Engineering, on the other hand, has produced devices that operate on the micron-scale and that combine electronic and mechanical systems. Microelectromechanical Systems (MEMS) offer advantages such as the integration of a variety of functions into a single device (i.e. lab-on-a-chip platforms) and portability for point-of-care diagnostics. This study utilizes a microscale electrochemical sensor for detecting BoNT apatamer hybridization, in which we first used top-down lithographic processing to define the pattern of the electrodes and then used bottom-up manufacturing to modify the surface molecular properties for reducing non-specific binding. The goal was to systemically examine the effects of the design parameters of an electrochemical DNA sensor. Four key design parameters were examined: the area of the working electrode, the area of the counter electrode, the separation distance between the working and counter electrodes, and the overlap length between the working and counter electrodes. Through a log-log analysis of the current generated, representing the signal or noise, across variations of the different parameters, the significance of each parameter in sensor performance was determined. We found that the area of the working electrode was important in the performance optimization of the sensor, while the performance seemed to be independent of the other three parameters. The output signal level increased with the area of the working electrode and the signal-to-noise ratio was about constant in the tested range.