1. Department of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 e-mail:
2. Department of Mechanical Engineering, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 e-mail:
3. Department of Mechanical Science and Engineering, University of Illinois Urbana-Champaign, 1206 W. Green St., Urbana, IL 61801 e-mail:
4. Robert Frederick Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY 14853 e-mail: