Demonstration of a wide range conductivity sensor for buffers on-demand manufacturing

Abstract

The aim of this work is to show the feasibility of an on-chip conductivity sensor for quality control during buffer preparation in biomanufacturing, using solutions with different chemical compositions. To optimize the sensor accuracy across a broad conductivity range (0.05 to 180 mS/cm), we selected a microfabricated four-electrode sensor and employed multi-point calibration to determine its apparent cell constant. Impedance spectra were captured (80 Hz to 80 kHz), followed by data post-processing to select resistive frequency bands based on the measured impedance phase angle. This study demonstrates sensor stability over 45 days in six solutions commonly used in buffer manufacturing processes and its compatibility with sanitization processes such as clean-in-place (CIP), and steam-in-place (SIP). Across all experiments, the sensor consistently showed a relative error below 5 % compared to a commercial sensor in static and dynamic conditions. The performance of the presented sensor, using the multi-point calibration, establishes it as a reliable tool for quality control in cost-effective, on-demand buffer manufacturing.