1. Department of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla, CA 92093, USA.
2. Van der Waals-Zeeman Institute, Institute of Physics, University of Amsterdam, Science Park 904, Amsterdam 1098XH, Netherlands.
3. Materials Science and Engineering Program, University of California, San Diego, La Jolla, CA 92093, USA.
4. Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093, USA.