1. Departments of Materials Science and Engineering, Mechanical Science and Engineering, and Electrical and Computer Engineering and Chemistry, University of Illinois at Urbana-Champaign, 1304 West Green Street, Urbana, IL 61801, USA.
2. Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, 405 North Mathews Avenue, Urbana, IL 61801, USA.
3. Materials Research Laboratory, University of Illinois at Urbana-Champaign, 104 South Goodwin Avenue, Urbana, IL 61801, USA.
4. Department of Electrical and Electronic Engineering and Information Systems, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
5. Departments of Civil and Environmental Engineering and Mechanical Engineering, Northwestern University, Evanston, IL 60208, USA.