A CMOS multiparameter biochemical microsensor with temperature control and signal interfacing

A fully integrated multiparameter microsensor chip is presented for continuous monitoring of concentrations of different blood gases (e.g., pH, PO₂, pCO₂), ions, and biomolecules, and for conductometric measurements. The chip can monitor up to seven different chemical substances depending on the membranes deposited on the sensor units (on-chip ion-sensitive field-effect transistors (ISFETs), amperometric and conductometric cell). The sensors, which are positioned in a flow channel, are surrounded by on-chip interfacing and processing electronics so that external readout goes via a simple data acquisition card. In addition, temperature control of the measured fluids and a onetime-use security check have been provided for proper operation. Fabrication was done in a standard 1.2-μm CMOS process to which extra postprocessing steps have been added for the chemical sensors and membranes. The chip operates at 5 V and the total die area is 25.7 mm². Full integration is obtained including the ISFETs and ISFET buffers, as well as a reference electrode structure, all integrated on the same chip in the same technology