Parallel measurement of multiple water parameters with a single sensor chip

The Fraunhofer Institute for Photonic Microsystems IPMS presents ground-breaking integration technology for the simultaneous measurement of various water parameters using ISFETs. The newly developed n-well integration technology makes it possible to measure pH values and nitrate, phosphate, and potassium concentrations in parallel and continuously with only one sensor chip. This innovation opens new horizons for environmental and bioanalytics.

ISFETs are compact, durable and simple to integrate. This makes them ideal for precise pH measurement and accurately determining the concentration of many ions in water, making them powerful tools in environmental and bioanalytics. Due to their resistance to breakage, they are already widely employed in pH measurement technology, particularly in food production. The company has now developed an n‑well technology that integrates several ISFETs on a single chip to be specifically functionalised with ion-selective layers.

This integration technology opens up the possibility of multifunctional ISFET arrays. In cooperation with research partners, further application-specific ion-selective coatings can be developed and integrated in the future. This enables the simultaneous and continuous measurement of different parameters such as pH, nitrate, phosphate and potassium concentration with only one sensor chip. Other parameters can be integrated into the system as needed.

"Such a measuring system, which can continuously record essential water parameters in real-time, has a huge market potential," says Dr Olaf R. Hild, head of the business unit Chemical Sensor Technology at Fraunhofer IPMS. "This opens up new possibilities for applications in environmental analysis, agriculture and water management, as well as in the rapidly growing market for indoor farming applications." "And," he adds with a smile, "with this technology, we have a unique position in Europe!"

The use of this technology should increase the efficiency and sustainability of agriculture by combining the measurements with external input, such as weather data. This would allow farmers to apply nutrients more precisely, resulting in savings on fertiliser costs and the reduction of environmental impact.

The ISFETs are based on MOS field-effect transistor technology. Electrical isolation, achieved by implanting phosphorus as n-dopant in a p-wafer, makes the integration of several ISFETs in an n-well possible. The sensor area in contact with the medium consists of a metal oxide layer, which can either function as a pH sensor or be coated with an ion-selective membrane. For each ion to be detected, an ISFET must be coated with a corresponding ion-selective membrane.

SENSOR+TEST, booth 1-317 in Nuremberg from June 11 to 13.