Emil Aaltonen Foundation granted him the Young Researcher Award from his doctoral dissertation (Effective Medium Studies of Dislocations and Surfaces in FCC Metal).
After his graduation, Häkkinen worked as a post-doctoral fellow at the Georgia Institute of Technology, Atlanta from November 1992 to August 1994.
University of Jyväskylä is organizing the International Symposium on Small Particles and Inorganic Clusters (ISSPIC) in August 2016.
He has studied electronic, optical, magnetic, chemical and catalytic properties of bare, supported, and ligand-protected metal nanoparticles.
Häkkinen developed a specific method in which he attached a self-made 1 to 3 nanometer sized gold particles onto the surface proteins of enteroviruses.