His major research contributions are in the areas of surface engineering, multifunctional thin films, small-scale materials and material-environment interactions. He has invented novel intensified plasma treatments for surface hardening and producing functionally gradient surface layers. In the area of nanomaterials, his group was the first to achieve self-assembling of perovskite-type oxides and metal/ceramic nanocomposite thin films with high aspect ratio. He has more than 300 publications (>7,000 research citations, h-index=44) and a large number of plenary, keynote and invited talks. His recent work focuses on scale effects on material properties, surface engineering by plasma processes and high temperature oxidation resistant coatings. His research program has attracted more than $18M from federal, state and industrial sources. Dr. Meletis has been a recipient of the William Fulbright Scholar Award and is the Editor-in-Chief of the Journal of Nano Research.