The integration of potentiometric and optical chemical sensor arrays.

Traditionally, miniaturized ion-selective electrodes (ISE) have been used in clinical applications; however, many clinically important ions cannot be detected by ISEs, or the concentration of the analyte under analysis cannot be detected in a clinically relevant range. It is possible to detect many additional ions or molecules using optical sensors, which also utilize chemically selective polymeric membranes. To improve the reliability, increase the number of detectable molecules, and improve the frugality of the data acquisition interface we integrated optical and potentiometric sensors onto the same integrated circuit. Several innovations were achieved in this research towards the integration of both optical and potentiometric sensors into a single system. First, the electrochemical performance of screen-printed potentiometric sensors was improved from nearly no response to near Nernstian response at concentrations greater than 100 mM. Second, a new, patented innovation involving the use of thick screen-printed and thin-film photopatterned wells or rings around the sensing sites was implemented to provide the ability to place the small (less than 300 mum) sensing sites within 200 mum of each other while maintaining membrane integrity, excellent adhesion, and electrochemical performance, thereby reducing size and cost. Third, optical sensors were integrated with the potentiometric sensors using silicon-on-insulator (SOI) p-i-n photo-diodes which have improved characteristics for signal response, necessary for the implementation of less than 10 mum thick (fast responding but low absorbance) optical chemical sensors. Fourth, commercially viable packaging for this chemical sensor system was developed. This Thesis research demonstrates the feasibility of mass production of integrated optical and potentiometric sensors, with CMOS circuitry, on the same chip. Arrays of these devices were produced with over 90% yields and thereby are mass producible, and provide both electrochemical slope and detection limits as good as their bulky counterparts. Additionally, in the optimal package the sensors require less than a microliter of sample volume, and provide improved signal-to-noise ratio, without the need for expensive interface hardware.Ph.D.Applied SciencesElectrical engineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/125386/2/3192661.pd