[HWgeek]

hfc99: you are right the PDN has a glass in it, however in the construction there are typically four layers;Top polyester layer coated with a transparent metallic conductive coating on the bottomAdhesive spacerGlass layer coated with a transparent metallic conductive coating on the topAdhesive layer on the backside of the glass for mounting.Since the top layer needs some flex to create the resistor divider network (ie find your finger press) its generally not made of glass.