skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Irreversible shear-induced vitrification of droplets into elastic nanoemulsions by extreme rupturing

Abstract

Many materials weaken through fracturing when subjected to extreme stresses. By contrast, we show that breaking down repulsive bits of matter dispersed in a viscous liquid can cause a dramatic and irreversible increase in the dispersion's elasticity. Anionically stabilized microscale emulsions subjected to a history of high-pressure microfluidic flow can develop an unusually large elastic modulus as droplets are ruptured to the nanoscale, yielding 'nanonaise'. As the droplet size approaches the Debye screening length, the nanoemulsion vitrifies. Consequently, the onset of elasticity for disordered uniform nanoemulsions can occur at droplet volume fractions far below maximal random jamming of spheres.

Authors:
 [1];  [1];  [2];  [2]
  1. Department of Chemistry and Biochemistry, University of California-Los Angeles, Los Angeles, California 90095 (United States)
  2. (United States)
Publication Date:
OSTI Identifier:
21072415
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. E, Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics; Journal Volume: 75; Journal Issue: 4; Other Information: DOI: 10.1103/PhysRevE.75.041407; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; DEBYE LENGTH; DROPLETS; ELASTICITY; EMULSIONS; FRACTURES; FRACTURING; LIQUIDS; NANOSTRUCTURES; RANDOMNESS; SHEAR; STRESSES; VITRIFICATION; YOUNG MODULUS

Citation Formats

Wilking, James N., Mason, Thomas G., Department of Physics and Astronomy, University of California-Los Angeles, Los Angeles, California 90095, and California NanoSystems Institute, University of California-Los Angeles, Los Angeles, California 90095. Irreversible shear-induced vitrification of droplets into elastic nanoemulsions by extreme rupturing. United States: N. p., 2007. Web. doi:10.1103/PHYSREVE.75.041407.
Wilking, James N., Mason, Thomas G., Department of Physics and Astronomy, University of California-Los Angeles, Los Angeles, California 90095, & California NanoSystems Institute, University of California-Los Angeles, Los Angeles, California 90095. Irreversible shear-induced vitrification of droplets into elastic nanoemulsions by extreme rupturing. United States. doi:10.1103/PHYSREVE.75.041407.
Wilking, James N., Mason, Thomas G., Department of Physics and Astronomy, University of California-Los Angeles, Los Angeles, California 90095, and California NanoSystems Institute, University of California-Los Angeles, Los Angeles, California 90095. Sun . "Irreversible shear-induced vitrification of droplets into elastic nanoemulsions by extreme rupturing". United States. doi:10.1103/PHYSREVE.75.041407.
@article{osti_21072415,
title = {Irreversible shear-induced vitrification of droplets into elastic nanoemulsions by extreme rupturing},
author = {Wilking, James N. and Mason, Thomas G. and Department of Physics and Astronomy, University of California-Los Angeles, Los Angeles, California 90095 and California NanoSystems Institute, University of California-Los Angeles, Los Angeles, California 90095},
abstractNote = {Many materials weaken through fracturing when subjected to extreme stresses. By contrast, we show that breaking down repulsive bits of matter dispersed in a viscous liquid can cause a dramatic and irreversible increase in the dispersion's elasticity. Anionically stabilized microscale emulsions subjected to a history of high-pressure microfluidic flow can develop an unusually large elastic modulus as droplets are ruptured to the nanoscale, yielding 'nanonaise'. As the droplet size approaches the Debye screening length, the nanoemulsion vitrifies. Consequently, the onset of elasticity for disordered uniform nanoemulsions can occur at droplet volume fractions far below maximal random jamming of spheres.},
doi = {10.1103/PHYSREVE.75.041407},
journal = {Physical Review. E, Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics},
number = 4,
volume = 75,
place = {United States},
year = {Sun Apr 15 00:00:00 EDT 2007},
month = {Sun Apr 15 00:00:00 EDT 2007}
}
  • We describe a method for creating discrete femtoliter-scale water-in-oil droplets on demand, based solely on a geometrically induced reduction in oil/water interfacial area at microfabricated junction orifices. This on-demand generation method is driven by self-shear of droplets due to interfacial tension induced forces resulting from a localized transition in microchannel height. The magnitudes of shear stresses involved appear to be significantly less than the shearing instabilities used to split off daughter droplets from aqueous mother plugs at microfabricated junctions in continuous water-in-oil segmented flows, which implies that this method may be better suited for studying biochemical reactions and reaction kineticsmore » in droplets of decreased volume without loss of chemical reactivity due to redistribution of surfactant density used to passivate the oil/water interface. Predictable droplet generation rates under constant pressure conditions or the gated formation of one, two or more droplets at a time with fixed pressure pulses have been demonstrated in a similar manner to active on-demand droplet generation strategies, but with a simpler system not needing actuation and sensing equipment beyond a pressure regulator.« less
  • First-principles calculations are employed to provide a fundamental understanding of the structural features, elastic anisotropy, shear-induced atomistic deformation behaviors, and its electronic origin of the recently proposed superhard t-SiCN. According to the dependences of the elastic modulus on different crystal directions, the t-SiCN exhibits a well-pronounced elastic anisotropy which may impose certain limitations and restrictions on its applications. The further mechanical calculations demonstrated that t-SiCN shows lower elastic moduli and ideal shear strength than those of typical hard substances of TiN and TiC, suggesting that it cannot be intrinsically superhard as claimed in the recent works. We find that themore » failure modes of t-SiCN at the atomic level during shear deformation can be attributed to the breaking of C-C bonds through the bonding evolution and electronic localization analyses.« less
  • We developed a microfluidic platform for splitting well-mixed, femtoliter-volume droplets from larger water-in-oil plugs, where the sizes of the daughter droplets were not limited by channel width. These droplets were separated from mother plugs at a microfabricated T-junction, which enabled the study of how increased confinement affected enzyme kinetics in droplets 4-10 {mu}m in diameter. Initial rates for enzyme catalysis in the mother plugs and the largest daughter drops were close to the average bulk rate, while the rates in smaller droplets decreased linearly with increasing surface to volume ratio. Rates in the smallest droplets decreased by a factor ofmore » 4 compared to the bulk rate. Traditional methods for detecting nonspecific adsorption at the water-oil interface were unable to detect evidence of enzyme adsorption, including pendant drop tensiometry, laser scanning confocal microscopy of drops containing labeled proteins in microemulsions, and epifluorescence microscopy of plugs and drops generated on-chip. We propose the slowing of enzyme reaction kinetics in the smaller droplets was the result of increased adsorption and inactivation of enzymes at the water-oil interface arising from transient interfacial shear stresses imparted on the daughter droplets as they split from the mother plugs and passed through the constricted opening of the T-junction. Such stresses are known to modulate the interfacial area and density of surfactant molecules that can passivate the interface. Bright field images of the splitting processes at the junction indicate that these stresses scaled with increasing surface to volume ratios of the droplets but were relatively insensitive to the average flow rate of plugs upstream of the junction.« less
  • Using multispeckle x-ray photon correlation spectroscopy, we have measured the slow, wave-vector-dependent dynamics of concentrated, disordered nanoemulsions composed of silicone oil droplets in water. The intermediate scattering function possesses a compressed exponential line shape and a relaxation time that varies inversely with wave vector. We interpret this dynamics as strain in response to local stress relaxation. The motion includes a transient component whose characteristic velocity decays exponentially with time following a mechanical perturbation of the nanoemulsions and a second component whose characteristic velocity is essentially independent of time. The steady-state characteristic velocity is surprisingly insensitive to the droplet volume fractionmore » in the concentrated regime, indicating that the strain motion is only weakly dependent on the droplet-droplet interactions.« less