[1] Johns Hopkins Univ, Chem & Biomol Engn, Baltimore, MD 21218 USA
[2] Univ Calif Santa Barbara, Dept Phys, Santa Barbara, CA 93106 USA
[3] Univ Calif Santa Barbara, Biomol Sci & Engn, Santa Barbara, CA 93106 USA
[4] Johns Hopkins Univ, Comp Sci, Baltimore, MD 21218 USA
[5] Nanofabricat Res Grp, Gaithersburg, MD USA