1. NanoMaterials Group, Laboratory of Physics and Center for New Materials, Helsinki University of Technology, P.O. Box 1000, 02044 VTT, Espoo, Finland, Mechanical Engineering, Yale University, P.O. Box 208286, New Haven, Connecticut 06520-8286, and VTT Biotechnology, P.O. Box 5100, 02150, Espoo, Finland