1. Department of Chemical Engineering University of Michigan Ann Arbor MI 48109 USA
2. Biointerfaces Institute University of Michigan Ann Arbor MI 48109 USA
3. Department of Pharmaceutical Sciences University of Michigan Ann Arbor MI 48109 USA
4. Department of Physics Technische Universitaet Darmstadt Darmstadt 64289 Germany
5. Department of Chemical Engineering University of California Santa Barbara Santa Barbara CA 93106 USA