From 1971 to 1974, ARPA supported research on "glassy" carbon, a unique foam material composed of pure carbon and that combined low weight, high strength, and chemical inertness. The program led to techniques for producing the material with an exceptionally porous, high surface area combined with high rigidity, low resistance to fluid flow, and resistance to very high temperatures in a non-oxidizing environment.
Eyed originally for roles in electro-chemistry because of its high surface area, the material proved suitable for surgical implants, especially heart valves. Development of the valves began about three years after the end of the ARPA program, with production commencing in 1985. In 1990, the U.S. Food and Drug Administration (FDA) gave its approval for using glassy carbon in implants in a valve market that grew within the decade to 100,000 units and a market value of $200 million. A related form, pyrolytic carbon, remains common in the inner orifice and leaflets of artificial valves.