Integrated Multisensor for FIA-Based Electronic Tongue Applications

The design, fabrication, and application of a monolithically integrated array of chemical sensors is presented. The multisensor chip includes six independent ion selective field effect transistors (ISFETs), a pair of interdigitated platinum electrodes, and a diode temperature sensor. Simultaneous polarization of multiple ISFETs is enabled by electrical isolation of the devices using two different approaches: by trenches and by p-n junction. The degradation of ISFET parameters by the fabrication steps of the interdigitated electrodes has been also studied and solutions consisting of additional annealing steps proposed. The multisensor chip has been assembled within a flow cell and applied as an electronic tongue to the measurement of bottled drinking water. Sensitivity to different ions has been achieved by deposition of organic membranes on top of the ISFET devices. Discrimination of different commercial waters by means of principal component analysis (PCA) of the data is demonstrated.