1. The idea
The patch would contain bacteria able to recognize compound that are precursor of diseases and give directly the result by a colored signal at the surface of the patch.
2. How to
Some new patches are selective membranes that permit diffusion only from one direction, here from blood to patch, it could prevent infection from our bacteria containing in the patch. Then, we would need to express on the outer membrane of the bacteria antibodies that could enabled the transduction of a specific signal.
Promising ! In fact it was our project until Ariel told us that Outer membrane vesicles and their applications could be as interesting as this project.
result : sadly to the trash :(