Acoustically induced breakup of levitated droplets

<p>The impact of atmospheric aerosol on the climate remains poorly understood. Organic aerosol makes up a significant fraction of total aerosol and is prevalent throughout the atmosphere. It can exist as a liquid, semi-solid or amorphous solid. The viscosity of organic aerosol will have an impact on transformations that organic aerosol will undergo during its lifetime such as evaporation and growth, heterogeneous and photochemical reactions as well as the ability to act as an ice nucleating particle.&#160; Therefore, it is of key importance to be able to determine aerosol viscosity over a range of atmospherically relevant conditions in order to better understand the impact of organic aerosol on the climate.</p> <p>Here we report proof of concept viscosity measurements of water droplets levitated in an electrodynamic balance over a range of temperatures. Charged droplets are levitated in a temperature and relative humidity-controlled environment allowing properties over a temperature range of 300 to 220 K to be studied. As the droplets evaporate they reach a point where Coulomb instabilities are induced resulting in droplet oscillations. The relaxation of these oscillations can then be probed to determine the droplet viscosity. Future work will involve determination of the viscosity of different types of organic aerosol over a broad temperature range.</p>

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Coalescence Dynamics of Acoustically Levitated Droplets

Micromachines ◽

10.3390/mi11040343 ◽

2020 ◽

Vol 11 (4) ◽

pp. 343 ◽

Cited By ~ 3

Author(s):

Koji Hasegawa ◽

Ayumu Watanabe ◽

Akiko Kaneko ◽

Yutaka Abe

Keyword(s):

Sound Pressure ◽

Phased Array ◽

Phased Arrays ◽

Industrial Applications ◽

Acoustic Levitation ◽

Droplet Dynamics ◽

Levitated Droplets ◽

Ultrasonic Phased Array ◽

Velocity Information ◽

The Impact

The contactless coalescence of a droplet is of paramount importance for physical and industrial applications. This paper describes a coalescence method to be used mid-air via acoustic levitation using an ultrasonic phased array system. Acoustic levitation using ultrasonic phased arrays provides promising lab-on-a-drop applications, such as transportation, coalescence, mixing, separation, evaporation, and extraction in a continuous operation. The mechanism of droplet coalescence in mid-air may be better understood by experimentally and numerically exploring the droplet dynamics immediately before the coalescence. In this study, water droplets were experimentally levitated, transported, and coalesced by controlled acoustic fields. We observed that the edges of droplets deformed and attracted each other immediately before the coalescence. Through image processing, the radii of curvature of the droplets were quantified and the pressure difference between the inside and outside a droplet was simulated to obtain the pressure and velocity information on the droplet’s surface. The results revealed that the sound pressure acting on the droplet clearly decreased before the impact of the droplets. This pressure on the droplets was quantitatively analyzed from the experimental data. Our experimental and numerical results provide deeper physical insights into contactless droplet manipulation for futuristic lab-on-a-drop applications.

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Enhancing Double-Beam Laser Tweezers Raman Spectroscopy (LTRS) for the Photochemical Study of Individual Airborne Microdroplets

Molecules ◽

10.3390/molecules24183325 ◽

2019 ◽

Vol 24 (18) ◽

pp. 3325 ◽

Cited By ~ 1

Author(s):

Jovanny Gómez Castaño ◽

Luc Boussekey ◽

Jean Verwaerde ◽

Myriam Moreau ◽

Yeny Tobón

Keyword(s):

Raman Spectroscopy ◽

Optical Tweezers ◽

Photochemical Reactions ◽

Laser Tweezers ◽

New Device ◽

Spatially Resolved ◽

Beam Laser ◽

Coupling System ◽

Double Beam ◽

Levitated Droplets

A new device and methodology for vertically coupling confocal Raman microscopy with optical tweezers for the in situ physico- and photochemical studies of individual microdroplets (Ø ≤ 10 µm) levitated in air is presented. The coupling expands the spectrum of studies performed with individual particles using laser tweezers Raman spectroscopy (LTRS) to photochemical processes and spatially resolved Raman microspectroscopy on airborne aerosols. This is the first study to demonstrate photochemical studies and Raman mapping on optically levitated droplets. By using this configuration, photochemical reactions in aerosols of atmospheric interest can be studied on a laboratory scale under realistic conditions of gas-phase composition and relative humidity. Likewise, the distribution of photoproducts within the drop can also be observed with this setup. The applicability of the coupling system was tested by studying the photochemical behavior of microdroplets (5 µm < Ø < 8 µm) containing an aqueous solution of sodium nitrate levitated in air and exposed to narrowed UV radiation (254 ± 25 nm). Photolysis of the levitated NaNO3 microdroplets presented photochemical kinetic differences in comparison with larger NaNO3 droplets (40 µm < Ø < 80 µm), previously photolyzed using acoustic traps, and heterogeneity in the distribution of the photoproducts within the drop.

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Laser ionization ion mobility spectrometric interrogation of acoustically levitated droplets

Analytical and Bioanalytical Chemistry ◽

10.1007/s00216-019-02167-5 ◽

2019 ◽

Vol 411 (30) ◽

pp. 8053-8061 ◽

Cited By ~ 2

Author(s):

Aleksandra Michalik-Onichimowska ◽

Toralf Beitz ◽

Ulrich Panne ◽

Hans-Gerd Löhmannsröben ◽

Jens Riedel

Keyword(s):

Ion Mobility ◽

Laser Ionization ◽

Levitated Droplets

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New technique for investigating phase transition processes of optically levitated droplets consisting of water and sulfuric acid

Journal of Geophysical Research Atmospheres ◽

10.1029/95jd03227 ◽

1996 ◽

Vol 101 (D14) ◽

pp. 19223-19229 ◽

Cited By ~ 11

Author(s):

Klaus Anders ◽

Norbert Roth ◽

Arnold Frohn

Keyword(s):

Phase Transition ◽

Sulfuric Acid ◽

New Technique ◽

Transition Processes ◽

Levitated Droplets

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Phase Diagram and Electrostatic Levitation Undercooling Studies of Polytetrahedral Phases in Ti-Fe-Si-O and Ti-Zr-Ni Alloys

MRS Proceedings ◽

10.1557/proc-643-k1.3 ◽

2000 ◽

Vol 643 ◽

Author(s):

T.K. Croat ◽

J.P. Davis ◽

A.K. Gangopadhyay ◽

K.F. Kelton ◽

G.W. Lee ◽

...

Keyword(s):

Undercooled Liquid ◽

Electrostatic Levitation ◽

State Transformation ◽

Solid State Transformation ◽

Ni Alloys ◽

New Information ◽

Long Duration ◽

Phase Fields ◽

Levitated Droplets ◽

Transformation Processes

AbstractNew information on the phase diagrams of Ti-Fe-Si-O and Ti-Zr-Ni alloys near the quasicrystal and rational approximant compositions is presented. α(TiFeSiO), the 1/1 rational approximant, is shown to form in a peritectic mode from the liquid, indicating the possibility to produce single-crystal samples. Very long duration annealing studies demonstrate unambiguously that the TiZrNi i-phase and 1/1 approximant form at low temperatures by a solid-state transformation; their phase fields do not extend to the liquidus temperatures. The first undercooling measurements of electrostatically-levitated droplets of the Ti-Zr-Ni alloys are presented. These nucleation studies provide new information on the structural relations between polytetrahedral phases and the undercooled liquid, and on the phase transformation processes. The reduced undercooling for the polytetrahedral phases in these alloys is less than for crystal phases of a similar composition, demonstrating a low interfacial energy between the polytetrahedral phase and the liquid.

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The use of an acoustic levitator to follow crystallization in small droplets by energy-dispersive X-ray diffraction

Journal of Applied Crystallography ◽

10.1107/s0021889806024915 ◽

2006 ◽

Vol 39 (5) ◽

pp. 771-773 ◽

Cited By ~ 22

Author(s):

Jork Leiterer ◽

Wolfram Leitenberger ◽

Franziska Emmerling ◽

Andreas F. Thünemann ◽

Ulrich Panne

Keyword(s):

Small Sample ◽

Sample Holder ◽

X Ray Diffraction ◽

Small Droplet ◽

X Ray ◽

Synchrotron Beam ◽

Levitated Droplets ◽

Diffraction Peaks ◽

Icsd Database ◽

Acoustic Levitator

For the investigation of small sample volumes, the use of an acoustic levitator was tested as a `sample holder' for hovering droplets in a synchrotron beam. It might be advantageous to use levitated droplets instead of samples confined in solid holders, especially for the study of crystallization processes where the influence of containing walls has to be minimized. In a first experiment, the crystallization of sodium chloride in a small droplet of aqueous solution has been followed with a time resolution of 30 s. The collected diffraction peaks are compared with data in the ICSD database.

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