1. Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
2. Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
3. Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
4. Bernstein Center Freiburg, University of Freiburg, 79104 Freiburg, Germany
5. Biomicrotechnology, Institute for Microsystems Engineering, University of Freiburg, 79110 Freiburg, Germany
6. Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany