1. Applied Mechanics Laboratory Department of Engineering Mechanics Center for Flexible Electronics Technology Tsinghua University Beijing 100084 P. R. China
2. Departments of Mechanical Engineering Northwestern University Evanston IL 60208 USA
3. The State Key Laboratory for Manufacturing and Systems Engineering School of Mechanical Engineering Xi'an Jiaotong University Xi'an 710049 P. R. China
4. Center for Bio‐Integrated Electronics Northwestern University Evanston IL 60208 USA
5. Department of Physics Tsinghua University Beijing 100084 P. R. China
6. Departments of Civil and Environmental Engineering Mechanical Engineering, and Materials Science and Engineering Center for Bio‐Integrated Electronics Northwestern University Evanston IL 60208 USA
7. Department of Materials Science and Engineering Biomedical Engineering Neurological Surgery Chemistry Mechanical Engineering Electrical Engineering and Computer Science Simpson Querrey Institute and Feinberg Medical School Center for Bio‐Integrated Electronics Northwestern University Evanston IL 60208 USA