1. The George W. Woodruff School of Mechanical Engineering Georgia Institute of Technology Atlanta GA 30332 USA
2. Shenzhen Key Laboratory of Nanobiomechanics Shenzhen Institutes of Advanced Technology Chinese Academy of Sciences Shenzhen 518055 China
3. State Key Laboratory for Strength and Vibration of Mechanical Structures School of Aerospace Engineering Xi'an Jiaotong University Xi'an 710049 China
4. Department of Mechanical Engineering University of Colorado Denver CO 80204 USA