A Parametric Design Study of an Electrochemical Sensor

Current microfabrication technologies rely on top-down, photolithographic techniques that are ultimately limited by the wavelength of light.

While systems for nanofabrication do exist, they frequently suffer from high costs and slow processing times, creating a need for a new manufacturing paradigm.

The combination of top-down and bottom-up fabrication approaches in device construction creates a new paradigm in micro- and nano-manufacturing.

The pre-requisite for the realization of the manufacturing paradigm relies on the manipulation of molecules in a deterministic and controlled manner.

To develop a microscale electrochemical biomarker sensor, we needed to first use top-down lithographic processing to define the pattern of the electrodes and then use bottom-up manufacturing to modify the surface molecular properties for reducing the non-specific binding.

This dissertation includes two tasks that involved the fabrication of electrodes to manipulate nanoparticles.

The use of AC electrokinetic forces, such as dielectrophoresis (DEP) and AC electroosmosis, is a promising technology for manipulating nano-sized particles in a parallel fashion.

The first task was to develop a three-electrode nano-focusing system to exploit electrokinetic forces in order to control the spatial distribution of nanoparticles in different frequency ranges.

Utilizing AC electrokinetics as a tool for the manipulation of nanoLEGOs (i.e. actin and actin-binding proteins) could be applied with nanoscale electrodes to dynamically assemble nanostructures.

A nanoelectrode system was designed and fabricated using electron beam lithography.

However, the research project was discontinued due to a funding issue.

The second task 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.

We found that the area of the working electrode was an important factor in the optimization of the performance 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.