1. Department of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109–2136, USA.
2. Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109–2125, USA.
3. Program in Macromolecular Science and Engineering, University of Michigan, Ann Arbor, MI 48109–2140, USA.
4. Department of Aerospace Engineering, University of Michigan, Ann Arbor, MI 48109–2140, USA.
5. Biophysics Research Division and Department of Chemistry, University of Michigan, Ann Arbor, MI 48109–1055, USA.