Determining hydrodynamic forces in bursting bubbles using DNA nanotube mechanics
Quantifying the mechanical forces produced by fluid flows within the ocean is critical to understanding the ocean's environmental phenomena. Such forces may have been instrumental in the origin of life by driving a primitive form of self-replication through fragmentation. Among the intense sources of hydrodynamic shear encountered in the ocean are breaking waves and the bursting bubbles produced by such waves. On a microscopic scale, one expects the surface-tension–driven flows produced during bubble rupture to exhibit particularly high velocity gradients due to the small size scales and masses involved. However, little work has examined the strength of shear flow rates in commonly encountered ocean conditions. By using DNA nanotubes as a novel fluid flow sensor, we investigate the elongational rates generated in bursting films within aqueous bubble foams using both laboratory buffer and ocean water. To characterize the elongational rate distribution associated with a bursting bubble, we introduce the concept of a fragmentation volume and measure its form as a function of elongational flow rate. We find that substantial volumes experience surprisingly large flow rates: during the bursting of a bubble having an air volume of 10 mm^3, elongational rates at least as large as ϵ = 1.0×10^8 s^(−1) are generated in a fragmentation volume of ∼2×10^(−6) μL. The determination of the elongational strain rate distribution is essential for assessing how effectively fluid motion within bursting bubbles at the ocean surface can shear microscopic particles and microorganisms, and could have driven the self-replication of a protobiont.
© 2015 National Academy of Sciences. Freely available online through the PNAS open access option. Edited by Eric D. Siggia, The Rockefeller University, New York, NY, and approved September 4, 2015 (received for review December 24, 2014). Published online before print October 26, 2015. The authors gratefully acknowledge Rebecca Schulman, Damien Woods, Paul Rothemund, Carter Swanson, Manu Prakash, John O. Dabiri, and Sandra Troian for helpful discussions. This work was supported by the National Science Foundation through Grants EMT-0622254, NIRT-0608889, CCF-0832824 (The Molecular Programming Project), and CCF-0855212. Author contributions: R.F.H., E.W., and B.Y. designed research; R.F.H. and B.Y. performed research; R.F.H., E.W., and B.Y. contributed new reagents/analytic tools; R.F.H., E.W., and B.Y. analyzed data; and R.F.H., E.W., and B.Y. wrote the paper. The authors declare no conflict of interest. This article is a PNAS Direct Submission. This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1424673112/-/DCSupplemental.
Published - PNAS-2015-Hariadi-E6086-95.pdf
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Supplemental Material - pnas.201424673SI.pdf
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