The only company of which I am aware is Somark, which manufactures RF inks for animals (see RFID Tattoos to Make a Mark on Cattle Tagging). The permanent animal-identification system works by tattooing each animal with dielectric ink. Data is encoded in the tattoo, and can be read remotely using a Somark interrogator.
If any of our readers know of other businesses that produce RF ink, please post information below.
—Mark Roberti, Founder and Editor, RFID Journal
Can an RFID Reader Be Programmed to Open Car Doors? »