Development of a porous silicon flow-through field effect sensing system for chemical and biological detection

With an increasing need for homeland security, and breakthrough advancements in sensing applications, the demand for highly sensitive, compact, biological and chemical sensing devices is evident. Macroporous silicon (MPS) is an ideal material for meeting these demands because it exhibits a large degree of internal surface area and is fully compatible with silicon technologies. Since the surface is sensitive to charged molecules, localized field effects from analytes interfaced with MPS will cause modulation of a space charge region in the semiconductor. In this work, a porous silicon based sensing system is designed, fabricated, and characterized. The unique properties of porous silicon and its promising qualities which facilitate the means for interfacing fluidic and electrical systems are investigated. A flow-though structure is used to deliver analytes to a MPS sensing membrane region and integrated electrodes contacting the MPS can be used to take electrical measurements. Fabricated sensors are enhanced by packaging them in a fluidic system which enables the future possibility of arrayed sensing platforms. To date this sensing system has successfully performed many sensing tasks applicable to the fields of science and technology. Unique measured capacitive responses of sensor to liquid phase acetone, ethanol, isopropyl alcohol, methanol, and toluene demonstrate detection and discrimination capabilities. The sensor has proven to be useful in monitoring the quality of air by detecting solvent vapor phase concentrations of \u3c 1 ppm. Packaged devices were used to monitor the quality of a water supply and were able to detect the presence of contaminants such as isopropyl alcohol. Application to the field of biology was demonstrated by observing a repeatable trend in measured capacitance during binding events between biotin and streptavidin proteins located in the MPS sensing membrane. The work presented herein shows that this sensing platform has a high degree of potential for repeatable and day-to-day reproducible detection in the areas of chemical and biological sensing