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Title: Dynamic measurements and simulations of airborne picolitre-droplet coalescence in holographic optical tweezers

Abstract

We report studies of the coalescence of pairs of picolitre aerosol droplets manipulated with holographic optical tweezers, probing the shape relaxation dynamics following coalescence by simultaneously monitoring the intensity of elastic backscattered light (EBL) from the trapping laser beam (time resolution on the order of 100 ns) while recording high frame rate camera images (time resolution <10 μs). The goals of this work are to: resolve the dynamics of droplet coalescence in holographic optical traps; assign the origin of key features in the time-dependent EBL intensity; and validate the use of the EBL alone to precisely determine droplet surface tension and viscosity. For low viscosity droplets, two sequential processes are evident: binary coalescence first results from the overlap of the optical traps on the time scale of microseconds followed by the recapture of the composite droplet in an optical trap on the time scale of milliseconds. As droplet viscosity increases, the relaxation in droplet shape eventually occurs on the same time scale as recapture, resulting in a convoluted evolution of the EBL intensity that inhibits quantitative determination of the relaxation time scale. Droplet coalescence was simulated using a computational framework to validate both experimental approaches. The results indicate that time-dependentmore » monitoring of droplet shape from the EBL intensity allows for robust determination of properties such as surface tension and viscosity. Finally, the potential of high frame rate imaging to examine the coalescence of dissimilar viscosity droplets is discussed.« less

Authors:
;  [1];  [2];  [3];  [4]
  1. School of Chemistry, University of Bristol, Bristol BS8 1TS (United Kingdom)
  2. Department of Mathematics, University of Leicester, Leicester LE1 7RH (United Kingdom)
  3. Mathematics Institute, University of Warwick, Coventry CV4 7AL (United Kingdom)
  4. Department of Chemistry, University of Leicester, Leicester LE1 7RH (United Kingdom)
Publication Date:
OSTI Identifier:
22679028
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 145; Journal Issue: 5; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; COALESCENCE; DROPLETS; EXPERIMENTAL DATA; HOLOGRAPHY; RELAXATION TIME; SIMULATION; SURFACE TENSION; TIME DEPENDENCE; TIME RESOLUTION; VISCOSITY

Citation Formats

Bzdek, Bryan R., Reid, Jonathan P., E-mail: j.p.reid@bristol.ac.uk, Collard, Liam, Sprittles, James E., and Hudson, Andrew J. Dynamic measurements and simulations of airborne picolitre-droplet coalescence in holographic optical tweezers. United States: N. p., 2016. Web. doi:10.1063/1.4959901.
Bzdek, Bryan R., Reid, Jonathan P., E-mail: j.p.reid@bristol.ac.uk, Collard, Liam, Sprittles, James E., & Hudson, Andrew J. Dynamic measurements and simulations of airborne picolitre-droplet coalescence in holographic optical tweezers. United States. doi:10.1063/1.4959901.
Bzdek, Bryan R., Reid, Jonathan P., E-mail: j.p.reid@bristol.ac.uk, Collard, Liam, Sprittles, James E., and Hudson, Andrew J. Sun . "Dynamic measurements and simulations of airborne picolitre-droplet coalescence in holographic optical tweezers". United States. doi:10.1063/1.4959901.
@article{osti_22679028,
title = {Dynamic measurements and simulations of airborne picolitre-droplet coalescence in holographic optical tweezers},
author = {Bzdek, Bryan R. and Reid, Jonathan P., E-mail: j.p.reid@bristol.ac.uk and Collard, Liam and Sprittles, James E. and Hudson, Andrew J.},
abstractNote = {We report studies of the coalescence of pairs of picolitre aerosol droplets manipulated with holographic optical tweezers, probing the shape relaxation dynamics following coalescence by simultaneously monitoring the intensity of elastic backscattered light (EBL) from the trapping laser beam (time resolution on the order of 100 ns) while recording high frame rate camera images (time resolution <10 μs). The goals of this work are to: resolve the dynamics of droplet coalescence in holographic optical traps; assign the origin of key features in the time-dependent EBL intensity; and validate the use of the EBL alone to precisely determine droplet surface tension and viscosity. For low viscosity droplets, two sequential processes are evident: binary coalescence first results from the overlap of the optical traps on the time scale of microseconds followed by the recapture of the composite droplet in an optical trap on the time scale of milliseconds. As droplet viscosity increases, the relaxation in droplet shape eventually occurs on the same time scale as recapture, resulting in a convoluted evolution of the EBL intensity that inhibits quantitative determination of the relaxation time scale. Droplet coalescence was simulated using a computational framework to validate both experimental approaches. The results indicate that time-dependent monitoring of droplet shape from the EBL intensity allows for robust determination of properties such as surface tension and viscosity. Finally, the potential of high frame rate imaging to examine the coalescence of dissimilar viscosity droplets is discussed.},
doi = {10.1063/1.4959901},
journal = {Journal of Chemical Physics},
number = 5,
volume = 145,
place = {United States},
year = {Sun Aug 07 00:00:00 EDT 2016},
month = {Sun Aug 07 00:00:00 EDT 2016}
}