1. Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign 1 , Urbana, Illinois 61801
2. Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign 2 , Urbana, Illinois 61801
3. Department of Chemical and Petroleum Engineering, University of Pittsburgh 3 , Pittsburgh, Pennsylvania 15260
4. Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign 4 , Urbana, Illinois 61801
5. Department of Materials Science and Engineering 5 , , Urbana, Illinois 61801
6. University of Illinois at Urbana-Champaign 5 , , Urbana, Illinois 61801
7. Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign 6 , Urbana, Illinois 61801