Ion selective field effect transistors: highly versatile tools for accurate detection of ions in water - WWEM 2018

Presented at WWEM 2018.
Nowadays, the tight environmental regulations demand a close control of the water quality in rivers, sea or even in waste waters. The water quality control require a regular monitoring due to continuous changes in several key parameters, such as seasonal water chemistry, overgrowing of plants, industrial waste and other factors. The chemical, physical and biological properties of the water define its quality. Currently, monitoring analytical parameters like the pH, temperature, conductivity, salinity, dissolved oxygen, chlorine and turbidity in water samples is quite trivial. Recently, the WHO (World Health Organization) issued some guidelines indicating that monitoring the amount of ions in water, in addition to the typical array of parameters, is paramount to assess its quality. However, the monitoring of these crucial ions is currently not possible in the majority of the portfolios of water analysis. At Wellinq we developed ion sensors that can enhance the current portfolio in water analysis. We produce and develop solid state, pH based ISFET sensors with superior analytical properties when compared to the conventional glass electrodes. Additionally, we develop and produce CHEMFET's, ISFET pH sensors functionalized with an ion selective membrane layer. Unlike the conventional ISE's (Ion Selective Electrodes), the CHEMFET's do not suffer from a strong noise increase upon miniaturization, that often results in poor sensor accuracy, due to the direct amplification of the surface potential, by the ISFET platform. Moreover, our vast membrane collection allows us to analyse a wide range of ions such as, sodium, potassium, nitrate, calcium, chlorine, ammonia and heavy metals as chromium and zirconium within a larger range of other ions. These sensors can be used either as a single robust probe or in an array format due to its chip format, based on the SOI (silicon on isolator, 0.8mm x 1.7mm) technology, ensuring multiple simultaneous ion measurements. These characteristics associated with their fast response time (≤2 seconds) make these sensors an excellent tool for water quality assessment. Wellinq sensors have been extensively validated by our customers, due to their superior analytical properties when compared to other ISFET based sensors. Our sensors are currently used in the detection of ions in rivers and in industrial aqueous waste and are regarded as a very powerful tool.