1. Laboratory for Soft Machines & Electronics School of Packaging Michigan State University East Lansing MI 48824 USA
2. Department of Mechanical Engineering Michigan State University East Lansing MI 48824 USA
3. Department of Electrical and Computer Engineering Michigan State University East Lansing MI 48824 USA
4. Department of Mechanical Engineering and Materials Science Duke University Durham NC 27708 USA
5. Beijing Institute of Nanoenergy and Nanosystems Chinese Academy of Sciences Beijing 100083 China
6. Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province Department of Engineering Mechanics Zhejiang University Hangzhou 310027 China