Revisiting lowest possible surface energy of a solid

The solid–vapor surface energy cannot be determined directly from the contact angle data because the Young equation includes three unknown interfacial energies. While the liquid–vapor energy is usually known, different theories can be used to exclude the solid–liquid energy, such as Antonoff, Zisman, Fowkes, and Owens and Wendt theories. These theories yield significantly different results for the solid–vapor surface energy. We revisit the claim that the lowest surface energy is 6.7 mJ m −2 of C 20 F 42 , while polytetrafluoroethylene’s surface energy is 22 mJ m −2 . These numbers can change significantly if a different theory is used.