April 10, 2025. The Fraunhofer Institute for Photonic Microsystems IPMS has reached another milestone in chemical liquid analysis. The electronics required to control the ion-sensitive field effect transistors (ISFET) have been miniaturized many times over. At the same time, it has been possible to cut manufacturing costs and reduce power consumption. The new electronics can be made available for direct use or for integration into in-house measuring systems.
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ISFETs enable the continuous and precise measurement of pH values by determining the concentration of certain ions in water or other aqueous media in real time. Following the outstanding development of niobium pentoxide-based ISFET pH sensors, Fraunhofer IPMS is once again reporting a major success: the new measuring systems operate with even lower power consumption than before. “After almost a year of development, we have succeeded in controlling our Nb2O5 ISFETs in such a way that they can measure continuously with a power consumption of less than 1.3 mW including electronics,” says Dr. Olaf R. Hild, Head of the Chemical Sensor Technology Business Unit at Fraunhofer IPMS. The power consumption of the sensor system is only 190 µW. Power consumption and size are essential parameters for mobile measuring systems.
Applications arise in continuous water monitoring and environmental analysis. However, long-term applications in medical technology, such as the analysis of various bodily fluids, also require power-efficient and small measuring systems.
The new control electronics, which will be presented at the “Sensor and Test” trade fair in Nuremberg in May, are particularly low-power and therefore more energy-efficient, as well as being very easy to handle and ready for immediate use. They consist of analog electronics (<1.3 mW) and digital electronics that can be connected via USB-C (approx. 100 mW), which enables rapid on-site calibration: “As the Fraunhofer IPMS ISFETs are extremely low-drift and exhibit almost perfect Nernst dependency, a single-point calibration is sufficient for the vast majority of applications,” explains electronics developer Hans-Georg Dallmann. This guarantees high accuracy, even over longer periods of time.
But Hild and his team are not yet satisfied with what they have achieved: “The next goal is smaller ISFET chips (< 1mm2) in order to be able to address size-limited applications. The cleanroom is ideally equipped for this challenge,” says technologist Falah Al-Falahi confidently.
Interested parties are cordially invited to exchange ideas with the scientists at Sensor + Test. From May 6 to 8, 2025, the latest developments and possible applications will be presented at stand 1-317 in Nuremberg. Appointments with the experts from Fraunhofer IPMS can be arranged in advance on the institute’s website.
The novel ISFET from Fraunhofer IPMS is based on metal-oxide-semiconductor (MOS) field-effect transistor technology, whereby the media-contacting sensor area consists of an amphoteric metal oxide layer. Hydronium or hydroxide ions from the measuring medium are reversibly deposited on this layer according to the pH value (pH-sensitive layer). The operating voltage (UDS) of the ISFET, which is applied between the source and the drain, leads to a current (IDS). This current is always kept constant during the measurement (constant charge mode). The voltage (UGS) between the source and the gate or the reference electrode (Ag/AgCl in 3M KCl) is then used as the measurement signal.
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Photo: Fraunhofer IPMS
