Publications

2018
Dynamics of spreading microbial swarms and films
Srinivasan, S., Kaplan, C.N. & Mahadevan, L., 2018. Dynamics of spreading microbial swarms and films. bioRxiv. Publisher's VersionAbstract
Bacterial swarming and biofilm formation are collective multicellular phenomena through which diverse microbial species colonize and spread over water-permeable tissue. During both modes of surface translocation, fluid uptake and transport play a key role in shaping the overall morphology and spreading dynamics. Here, using Bacillus subtilis as our model experimental system, we develop a generalized two-phase thin-film model that couples hydrodynamics, mechanics, osmotic flux and nutrient transport to describe the expansion of both highly motile bacterial swarms, and sessile bacterial biofilms. We show that swarm expansion corresponds to steady-state solutions in a nutrient-rich, capillarity dominated regime. In contrast, biofilm colony growth is described by transient solutions associated with a nutrient-limited, extracellular polymer stress driven limit. We apply our unified framework to explain a range of recent experimental observations associated with the shape, form and dynamics of Escherichia coli and Bacillus subtilis swarms and biofilms. Our results demonstrate how hydrodynamics and transport serve as key physical constraints in regulating biological organization and function in microbial communities.
Matrix Production and Sporulation in Bacillus subtilis Biofilms Localize to Propagating Wave Fronts
Srinivasan, S., et al., 2018. Matrix Production and Sporulation in Bacillus subtilis Biofilms Localize to Propagating Wave Fronts. Biophysical Journal , 114 (6) , pp. 1490–1498. Publisher's Version
2017
Wrinkling instability of an inhomogeneously stretched viscous sheet
Srinivasan, S., Wei, Z. & Mahadevan, L., 2017. Wrinkling instability of an inhomogeneously stretched viscous sheet. Physical Review Fluids , 2 (7) , pp. 074103. Abstract Article (pdf)
2016
Saranadhi, D., et al., 2016. Sustained drag reduction in a turbulent flow using a low-temperature Leidenfrost surface. Science Advances , 2 (10). Publisher's VersionAbstract
Skin friction drag contributes a major portion of the total drag for small and large water vehicles at high Reynolds number (Re). One emerging approach to reducing drag is to use superhydrophobic surfaces to promote slip boundary conditions. However, the air layer or “plastron” trapped on submerged superhydrophobic surfaces often diminishes quickly under hydrostatic pressure and/or turbulent pressure fluctuations. We use active heating on a superhydrophobic surface to establish a stable vapor layer or “Leidenfrost” state at a relatively low superheat temperature. The continuous film of water vapor lubricates the interface, and the resulting slip boundary condition leads to skin friction drag reduction on the inner rotor of a custom Taylor-Couette apparatus. We find that skin friction can be reduced by 80 to 90% relative to an unheated superhydrophobic surface for Re in the range 26,100 <= Re <= 52,000. We derive a boundary layer and slip theory to describe the hydrodynamics in the system and show that the plastron thickness is h = 44 ± 11 μm, in agreement with expectations for a Leidenfrost surface.
Ling, H., et al., 2016. High-resolution velocity measurement in the inner part of turbulent boundary layers over super-hydrophobic surfaces. Journal of Fluid Mechanics , 801 , pp. 670–703. Publisher's Version
2015
Designing Robust Hierarchically Textured Oleophobic Fabrics
Kleingartner, J.A., et al., 2015. Designing Robust Hierarchically Textured Oleophobic Fabrics. Langmuir , 31 (48) , pp. 13201–13213.
Srinivasan, S., et al., 2015. Sustainable drag reduction in turbulent Taylor-Couette flows by depositing sprayable superhydrophobic surfaces. Physical Review Letters , 114 , pp. 014501.
2014
Quantification of feather structure, wettability and resistance to liquid penetration (featured on MIT news)
Srinivasan, S., et al., 2014. Quantification of feather structure, wettability and resistance to liquid penetration (featured on MIT news). Journal of The Royal Society Interface , 11 (96).
Palangetic, L., et al., 2014. Dispersity and spinnability: Why highly polydisperse polymer solutions are desirable for electrospinning. Polymer , 55 , pp. 4920 - 4931.
Rykaczewski, K., et al., 2014. Dropwise condensation of low surface tension fluids on omniphobic surfaces. Scientific reports , 4.
2013
Drag reduction for viscous laminar flow on spray-coated non-wetting surfaces
Srinivasan, S., et al., 2013. Drag reduction for viscous laminar flow on spray-coated non-wetting surfaces. Soft Matter , 9 , pp. 5691. Article (pdf)
Park, K.-C., et al., 2013. Optimal Design of Permeable Fiber Network Structures for Fog Harvesting. Langmuir , 29 (43) , pp. 13269-13277.
Kleingartner, J.A., et al., 2013. Utilizing Dynamic Tensiometry to Quantify Contact Angle Hysteresis and Wetting State Transitions on Nonwetting Surfaces. Langmuir , 29 , pp. 13396-13406.
2011
Srinivasan, S., McKinley, G.H. & Cohen, R.E., 2011. Assessing the Accuracy of Contact Angle Measurements for Sessile Drops on Liquid-Repellent Surfaces. Langmuir , 27 , pp. 13582–13589.
Srinivasan, S., et al., 2011. Solution spraying of poly(methyl methacrylate) blends to fabricate microtextured, superoleophobic surfaces. Polymer , 52 , pp. 3209–3218.