1. Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA.
2. School of Mechanical and Aerospace Engineering, Nanyang Technological University, 639798 Singapore, Republic of Singapore.
3. School of Chemical and Biomedical Engineering, Nanyang Technological University, 639798 Singapore, Republic of Singapore.
4. Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana-Champaign, IL 61801, USA.
5. Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA.