1. CAS Center for Excellence in NanoscienceBeijing Key Laboratory of Micro‐nano Energy and SensorBeijing Institute of Nanoenergy and NanosystemsChinese Academy of Sciences Beijing 100083 P. R. China
2. Beijing Advanced Innovation Centre for Biomedical EngineeringBeihang UniversityKey Laboratory for Biomechanics and Mechanobiology of Ministry of EducationSchool of Biological Science and Medical EngineeringBeihang University Beijing 100083 P. R. China
3. National Research Center for Rehabilitation Technical Aids Beijing 100176 P. R. China
4. School of Nanoscience and TechnologyUniversity of Chinese Academy of Sciences Beijing 100049 P. R. China
5. School of Materials Science and EngineeringGeorgia Institute of Technology Atlanta GA 30332‐0245 USA
6. Center on Nanoenergy ResearchSchool of Physical Science and TechnologyGuangxi University Nanning 530004 P. R. China