Multiparameter Sensor Chip with Barium Strontium Titanate as Multipurpose Material

Abstract

It is well known that biochemical and biotechnological processes are strongly dependent and affected by a variety of physico‐chemical parameters such as pH value, temperature, pressure and electrolyte conductivity. Therefore, these quantities have to be monitored or controlled in order to guarantee a stable process operation, optimization and high yield. In this work, a sensor chip for the multiparameter detection of three physico‐chemical parameters such as electrolyte conductivity, pH and temperature is realized using barium strontium titanate (BST) as multipurpose material. The chip integrates a capacitively coupled four‐electrode electrolyte‐conductivity sensor, a capacitive field‐effect pH sensor and a thin‐film Pt‐temperature sensor. Due to the multifunctional properties of BST, it is utilized as final outermost coating layer of the processed sensor chip and serves as passivation and protection layer as well as pH‐sensitive transducer material at the same time. The results of testing of the individual sensors of the developed multiparameter sensor chip are presented. In addition, a quasi‐simultaneous multiparameter characterization of the sensor chip in buffer solutions with different pH value and electrolyte conductivity is performed. To study the sensor behavior and the suitability of BST as multifunctional material under harsh environmental conditions, the sensor chip was exemplarily tested in a biogas digestate.

Capacitive Field-Effect EIS Chemical Sensors and Biosensors: A Status Report

“…In addition, Ta 2 O 5 -gate EIS pH sensors were applied for measuring the extracellular acidification rate of Escherichia coli upon glucose pulses [ 65 ]. Further examples are EIS sensors with BST films as pH-sensitive material for the pH control in a biogas digestate [ 56 ] or an estimation of the acid content in rancid butter samples with a Si 3 N 4 -gate EIS pH sensor [ 66 ]. Finally, EIS pH sensors with Ta 2 O 5 films prepared by radio frequency magnetron sputtering were utilized for the real-time quantitative detection of DNA (deoxyribonucleic acid) amplification via loop-mediated isothermal amplification [ 36 ].…”

Multi‐parameter sensing using high‐k oxide of barium strontium titanate

“…In this contribution, the BST layer served as a transducer material for the polyelectrolyte and H 2 O 2 sensing as well as insulator layer for the contactless conductivity sensor. In it was proven that the BST material exhibits also pH‐sensitive characteristics. Moreover, the BST thin film protects the metal electrodes of the temperature sensor.…”

“…Recently, we have reported on a Si‐based sensor chip covered with a high‐ k BST layer for the detection of pH, electrolyte conductivity, and temperature . In the present study, a novel Si‐based sensor containing Pt interdigitated electrodes (IDE) covered with a thin BST layer has been developed for a multi‐parameter chemical sensing approach.…”

Novel probes for pH and dissolved oxygen measurements in cultivations from millilitre to benchtop scale

“…Ion-selective field effect transistors (ISFETs), which are essentially unbreakable solid-state sensors, comprise a semiconductor component that is modified with a pH-sensitive layer consisting of an inorganic gate oxide such as Ta 2 O 5 (Bergveld 2003). ISFET pH sensors have successfully been applied to monitor fermentation processes (Krommenhoek et al 2008;Bäcker et al 2011) and used to measure pH in a biogas digestate (Huck et al 2014). These sensors can be very small in size and are therefore suitable for microbioreactors (Maharbiz et al 2004).…”