1. Postdoctoral Researcher, Dept. of Mechanical Engineering, Aalto Univ., Espoo 00076, Finland (corresponding author).
2. Associate Professor, Dept. of Mechanical Engineering, Aalto Univ., Espoo 00076, Finland.
3. Research Fellow, Chinese Academy of Sciences Key Laboratory of Microscale Magnetic Resonance and Dept. of Modern Physics, Univ. of Science and Technology of China, Hefei 230026, China.