1. Laboratory for Biomaterials, Institute for Biotechnology and Helmholtz-Institute for Biomedical Engineering, RWTH Aachen University, Pauwelsstraße 20, D-52074 Aachen, Germany
2. Chair of Micro- and Nanosystems and Institute of Materials in Electrical Engineering 1, RWTH Aachen University, Sommerfeldstraße 24, D-52074 Aachen, Germany