1. Department of Materials Science and Engineering, Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
2. School of Chemical Engineering, Sungkyunkwan University (SKKU), Suwon 440-746, Korea.
3. Department of Anesthesiology, Division of Basic Research, Washington University School of Medicine, St. Louis, MO 63110, USA.
4. Washington University Pain Center, Washington University School of Medicine, St. Louis, MO 63110, USA.
5. Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, MO 63110, USA.
6. Division of Biological and Biomedical Sciences, Washington University School of Medicine, St. Louis, MO 63110, USA.
7. Department of Civil and Environmental Engineering, Department of Mechanical Engineering, and Institute for Public Health and Medicine, Northwestern University, Evanston, IL 60208, USA.
8. Department of Mechanical and Aerospace Engineering, University of Miami, Coral Gables, FL 33146, USA.
9. Soft Matter Research Center and Department of Civil Engineering, Zhejiang University, 38 Zheda Road, Hangzhou 310027, China.
10. Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61802, USA.
11. Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61802, USA.
12. Department of Biomedical Engineering, Tufts University, Medford, MA 02115, USA.
13. Department of Physics, Tufts University, Medford, MA 02115, USA.
14. Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61802, USA.