1. State Key Laboratory of Advanced Welding and Joining School of Materials Science and Engineering Harbin Institute of Technology Harbin 150001 P. R. China
2. Innovative Center for Flexible Devices (iFLEX) Max Planck – NTU Joint Lab for Artificial Senses School of Materials Science and Engineering Nanyang Technological University 50 Nanyang Avenue Singapore 639798 Singapore
3. Research Center for Neural Engineering Shenzhen Institutes of Advanced Technology Chinese Academy of Sciences Shenzhen 518055 China
4. Institute of Materials Research and Engineering Agency for Science Technology and Research (A*STAR) 2 Fusionopolis Way Singapore 138634 Singapore