SBIR-STTR Award

This Small Business Innovation Research Phase I project will provide a powerful tool for monitoring chemical, biological and environmental processes. A major cost component and obstacle of using potentiometric sensors in these applications is the need for frequent calibration and maintenance of the sensor. The foremost cause of periodic calibration and maintenance is due to a variation in the liquid junction, the interface between the reference electrode and the sample. The liquid junction is unavoidable in potentiometric sensors, and is the major limiting factor in the accuracy and operational life of pH sensors and other ion-selective electrodes. Recent developments in microfluidics and nanotechnology provide the means to develop long-lived, invariant, and reproducible liquid junctions that significantly reduce the need for sensor recalibration and maintenance. Reference electrodes using this new liquid junction will find application in all potentiometric sensors. The feasibility of developing an invariant and constant liquid junction will be demonstrated. Improved process control and significant savings in operational costs will make this reference technology the new sensor design requirement. The potential is also great for using this new technology as a basic building block in microfluidic sensor devices that utilize potentiometric microsensors. Such microfluidic devices are estimated by many sources to be a multi-billion dollar industry in the next decade.

This Small Business Innovation Research (SBIR) Phase II project will develop a long-lived, stable reference electrode that dramatically improves potentiometric measurements, such as pH, redox, and other ion-specific measurements. The new reference electrode exploits recent developments in microfluidics and nanotechnology to stabilize the liquid-junction potential, a source of error and a cause of frequent sensor calibration and maintenance. Stabilizing the liquid-junction potential of the reference electrode opens a new realm of potentiometric sensor design and application. The technical feasibility of this innovative electrode was demonstrated in the Phase I project. Testing in a variety of environments showed variations less than 0.5 mV in the reference electrode potential over an 8 hour period and response times less than 60 seconds, compared to potential variations up to 20 mV and response times of over an hour for conventional reference electrodes. The flow of electrolyte through the junction was less than 0.1 l per minute, or 50 ml per year of continuous operation. The Phase II project will develop assembly processes, more robust structures, and develop and build sensors for field-tests. The potential commercial application reduction in sensor calibration and sensor replacement which would save the US process industries approximately $240 million per year in sensor costs and labor expenses. Exports of US manufactured sensors with this technology will significantly increase as foreign process industries seek similar cost savings. Furthermore, this reference electrode can serve as a basic building block in microfluidic sensors, estimated to be a multi-billion dollar industry in the next decade.