[1] Swiss Fed Inst Technol, Inst Robot & Intelligent Syst, CH-8092 Zurich, Switzerland
[2] Swiss Fed Inst Technol, CH-8092 Zurich, Switzerland
[3] Swiss Fed Inst Technol, Particle Technol Lab, CH-8092 Zurich, Switzerland
[4] Harvard Univ, Sch Publ Hlth, Ctr Nanotechnol & Nanotoxicol, Boston, MA 02115 USA
[5] Harvard Univ, Sch Engn & Appl Sci, Wyss Inst Biologically Inspired Engn, Cambridge, MA 02318 USA