1. Department of Biology, Lewis & Clark College, Portland, OR, USA
2. Department of Integrative Biology, University of California, Berkeley, CA, USA
3. Department of Mechanical Engineering, Stanford University, Stanford, CA, USA
4. Department of Applied Physics, Stanford University, Stanford, CA, USA
5. Laboratoire PPMD, ESPCI-CNRS-UPMC, Paris, France
6. Department of Physics, Lewis & Clark College, Portland, OR, USA