Cross-polarized Near-UV Detector for In-line Quality Control of PEM Materials

Modern fuel cells have been in development since the 1960s and stand on the cusp of commercialization, but are held back by high manufacturing costs and expensive catalysts. Membrane costs can be as much as the 45% of the total cost of a commercial fuel cell system. Manufacturing defects in the membrane can cause cell failures that can cascade and cause complete stack failure, which is expensive and time consuming to resolve. For example, small pin hole leaks in a single cell can limit the current through the whole stack. Similarly, slight gradients in membrane thickness can cause stresses in complete stacks that cause the brittle graphite spacers to fracture once the stack is assembled. These defects are often not discovered until after costly catalyst has been irreversibly applied, leading to wasted materials and downtime of the membrane extrusion process. There is a need for some form of autonomous quality control in the early stages of fuel cell membrane manufacturing. We propose using near-ultraviolet light to infer information on changes to membrane film thickness, composition, and defects with a single detector, light source, and cross polarizing filters. This Cross-Polarized Near-UV CP-NUV) detector will simultaneously measure membrane thickness and determine and quantify membrane defects in real-time on an in-line roll-to-roll polymer manufacturing line. This information will be relayed to a printer to mark defective membranes for exclusion from catalyst coating and facilitate rapid fixes to membrane extrusion, improving line efficiency and reducing waste. This approach allows two measurement principles to be achieved with a single low-cost detector and light source with no moving parts. The CP-NUV detector will help drive down costs of fuel cell membranes which are often still too high to compete with conventional power generation equipment. With early detection of defects, defective material can be removed from the production line before further coating or assembly steps, reducing costs by minimizing waste of platinum catalyst material, labor, and customer returns. The CP-NUV detector is not limited to fuel cell membranes and other membrane manufacturing processes can also benefit from improved quality control devices.