Composite articles having diffusion barriers and devices incorporating them

A composite article (10) comprises two polymeric substrate layers (20, 24), each of which has at least a diffusion-inhibiting barrier (30, 34) on one of the surfaces. The diffusion-inhibiting barriers (30, 34) are disposed such that they face each other within the composite article (10). Electronic devices (110) are disposed on such composite article (10) to reduce the rate of diffusion of chemical species in the environment into the devices (110).