Finally, we have shown that these multilayers can be effectively fabricated on flexible substrates of transparent, biaxially oriented polyethylene terephthalate (Mylar) sheets (Fig. 4). These sensors were found to maintain their structural integrity and function even after multiple swelling/de-swelling cycles. The ability to prepare these sensors on flexible substrates opens the door to use in a variety of contexts, for example, as wearable patches, or in packaging applications.