Optics Breathe New Life into Oxygen Sensing: Sol-Gel Chemistry, Combined with Optical Fibre, Offers a Novel Approach to Measuring Dissolved Oxygen and pH Levels with Many Promising new Applications

Advances in high-performance sensor materials and optoelectronics have enabled novel optical sensors for use in a diverse array of markets including the life sciences, environmental, food and beverage, process control, and aviation. Compared to traditional electrochemical sensing techniques such as galvanic, paramagnetic, and fuel cell sensors, these optical sensors (sometimes called \\"optrodes,\\" as in optical electrodes) can be made in small, customizable form factors. They also have faster response, provide long-term calibration-free stability, are chemically inert, and couple easily to optical fibres for remote measurements. The principle of operation for optrodes is to trap a target-sensitive fluorophore or pH indicator dye in a host matrix that can then be applied to the tip of a fibre, flat substrate, adhesive membrane, or other surface. Optical fibres are particularly versatile because they can be made into probes of many sizes and shapes and can be jacketed for deployment in harsh environments. The sensing portion of the fibre probe is the tip, which can be made in sizes from 50 to more than 1000 μm in diameter.