A macroporous silicon field effect sensing system for liquid phase solvent detection

Integration of electrical and fluidic systems for the design and fabrication of a system-on-chip (SOC) capable of sensing various liquid phase solvents is reported. A monolithic integration strategy makes use of macroporous silicon (MPS) as a gateway to interface the electrical and fluidic domains. In doing this, the MPS material, acting as a sensing membrane, is used in a flow-through structure to transport an analyte, or fluidic sample under investigation, from fluidic channels on one side of the chip to sensing electrodes on the other. A fluid/oxide/semiconductor interface results in the modulation of a space charge region in the semiconductor where real-time measurements are used to detect and distinguish between various solvents. To date, the fluidic system has delivered liquid sample sizes as small as 2 mul. Selected test solvents, i.e. acetone, ethanol, isopropyl alcohol, methanol, and toluene have generated a measured change in capacitance up to 11% and have been detected with specificity. The sensing device has a high degree of reusability and does not require heating or other solvent drive-out methods often necessitated in other sensing devices