Since Professor Yu's formal retirement in 2004, he has been engaged in scholarly activity in a limited scope, with no postdoctoral associates or graduate students. He has been writing up his unpublished work, writing a textbook, reviewing manuscripts for journals and proposals for granting agencies, consulting for industrial companies, participating in various advisory boards of research institutes and centers, attending technical conferences and making some contributions to activities of scientific societies. He has also been active in the Korean Studies Initiatives of the Center for East Asian Studies at UW-Madison.
Professor Yu's interest in research, however, remains at the same level as before his retirement. It consists of: 1) transport and dynamics of macromolecules in bulk, solution and gels; 2) interfacial equilibrium and dynamic phenomena of amphiphiles including polymeric amphiphiles ; 3) biomedical applications of surface functionalized polymeric materials; 4) organic-inorganic composites for biocompatible uses.