1. Department of Electrical Engineering, Stanford University, Stanford, CA, USA.
2. Department of Materials Science and Engineering, Stanford University, Stanford, CA, USA.
3. Department of Bioengineering, Stanford University, Stanford, CA, USA.
4. Department of Chemistry, Stanford University, Stanford, CA, USA.
5. Department of Chemical Engineering, Stanford University, Stanford, CA, USA.
6. Xerox Palo Alto Research Center, Palo Alto, CA, USA.