Microfabricated electrochemical sensors for exhaustive coulometry applications

The development of microfabricated electrochemical systems suitable for deployment in sensor networks that operate with a minimum of operator intervention are of great interest; therefore, a coulometric sensing system for exhaustive coulometry with the potential for calibration-free operation has been designed, fabricated and evaluated to support such development. The sensor chips were microfabricated onto a silicon substrate and contained a variety of specially designed thin-film gold working electrodes (ranging from one to five per chip) and a Ag/AgCl pseudo-reference electrode. A custom flow cell containing fluidic connections and counter electrode chamber was also constructed to integrate the sensor and to create an electrolysis chamber with a fixed volume. Different chip designs were evaluated as exhaustive coulometric sensors in terms of reproducibility and longevity using Fe(CN)63−/4− as model analytes. The relative standard deviation (RSD) for a chip tested over a period of 42 days was 5.5% whereas the sensor-to-sensor reproducibility was within 6.3%.