1. Macromolecules Innovation Institute, Virginia Tech, Blacksburg, Virginia 24061, United States
2. Department of Mechanical Engineering, Soft Materials and Structures Lab, Virginia Tech, Blacksburg, Virginia 24061, United States
3. Department of Materials Science and Engineering, Iowa State University, Ames, Iowa 50011, United States
4. Sensors and Electron Devices Directorate, U.S. Army Research Laboratory, Adelphi, Maryland 20783, United States