The main bioprocess variables that are continuously measured are pH, dissolved oxygen (DO), and dissolved car- bon dioxide (DCO₂). Less common variables are redox, concentrations of substrate and product concentrations, product activity, etc. Recently, pH and DO have been measured using optical chemical sensors due to their small form factor and convenience in use. These sensors are typically interrogated using a lab grade spectrometer, or with the help of a low-cost, tailor-made optoelectronic transducer that is designed around the optical sensor. Recently, we proposed a new class of optoelectronic transducers that are capable of monitoring several different optical sensors without the need to switch the optics or hardware when changing the type of sensor. This allows flexibility closer to the lab-grade devices at a price point of a dedicated sensor.

In this work, we have demonstrated a universal optical platform capable of monitoring pH or DO sensors. It uses the principle of ratio-metric fluorescence measurements for pH and fluorescence lifetime measurements for DO. The platform is capable of seamlessly switching between these two modes. It is also capable of auto recognition of the sensor type. The platform can operate both with patch-type or fiber optic type of sensors. The platform has measurement accuracy of about 0.08 pH units and approximately 5 % air saturation with oxygen. Additionally, an approach to obtain identical calibrations between several devices is presented.

The described platform has been tested in actual bioprocesses and has been found adequate for continuous bioprocess monitoring.

Date Published: 13 May 2015
PDF: 10 pages
Proc. SPIE 9486, Advanced Environmental, Chemical, and Biological Sensing Technologies XII, 94860P (13 May 2015); doi: 10.1117/12.2179721

Published in SPIE Proceedings Vol. 9486:
Advanced Environmental, Chemical, and Biological Sensing Technologies XII
Tuan Vo-Dinh; Robert A. Lieberman; Günter G. Gauglitz, Editor(s)