To help realize stable droplet manipulation, we present a study on the physical mechanism of interfacial instability and droplet atomization dynamics in acoustic levitation with ultrasonic phased arrays. Acoustic levitation is highly applicable in the fields of analytical chemistry and biology because container-less processing can prevent undesirable wall effects, such as nucleation and contamination resulting from the container walls. Although many studies demonstrated the atomization behavior in single-axis acoustic levitation, the breakup characteristics of levitated droplets in ultrasonic phased array levitation have been less studied. Here, we visualized the atomization behavior of ethanol, ethanol solution, and silicone oil droplets using a high-speed camera. The time evolution of the interfacial velocity of the droplets indicates a threshold for the droplet atomization. To elucidate atomization dynamics, the critical interfacial velocities of the levitated droplet immediately before its atomization are discussed and compared to the theoretical prediction based on the Kelvin–Helmholtz instability. Our experimental findings provide deeper physical insights into the levitation stability of droplets in ultrasonic phased array levitation for futuristic lab-in-a-drop applications.

1.
S.
Santesson
and
S.
Nilsson
, “
Airborne chemistry: Acoustic levitation in chemical analysis
,”
Anal. Bioanal. Chem.
378
,
1704
(
2004
).
2.
R.
Tuckermann
,
L.
Puskar
,
M.
Zavabeti
,
R.
Sekine
, and
D.
McNaughton
, “
Chemical analysis of acoustically levitated drops by Raman spectroscopy
,”
Anal. Bioanal. Chem.
394
,
1433
(
2009
).
3.
D.
Zang
,
J.
Li
,
Z.
Chen
,
Z.
Zhai
,
X.
Geng
, and
B. P.
Binks
, “
Switchable opening and closing of a liquid marble via ultrasonic levitation
,”
Langmuir
31
,
11502
(
2015
).
4.
A.
Scheeline
and
R. L.
Behrens
, “
Potential of levitated drops to serve as microreactors for biophysical measurements
,”
Biophys. Chem.
165-166
,
1
(
2012
).
5.
M.
Sundvik
,
H. J.
Nieminen
,
A.
Salmi
,
P.
Panula
, and
E.
Hæggström
, “
Effects of acoustic levitation on the development of zebrafish, Danio rerio, embryos
,”
Sci. Rep.
5
,
13596
(
2015
).
6.
C.
Bouyer
,
P.
Chen
,
S.
Güven
,
T. T.
Demirtaş
,
T. J. F.
Nieland
,
F.
Padilla
, and
U.
Demirci
, “
A bio-acoustic levitational (BAL) assembly method for engineering of multilayered, 3D brain-like constructs, using human embryonic stem cell derived neuro-progenitors
,”
Adv. Mater.
28
,
161
(
2016
).
7.
W. J.
Xie
,
C. D.
Cao
,
Y. J.
, and
B.
Wei
, “
Eutectic growth under acoustic levitation conditions
,”
Phys. Rev. E
66
,
061601
(
2002
).
8.
Y. J.
,
W. J.
Xie
, and
B.
Wei
, “
Observation of ice nucleation in acoustically levitated water drops
,”
J. Appl. Phys. Lett.
87
,
184107
(
2005
).
9.
D. L.
Geng
,
W. J.
Xie
, and
B.
Wei
, “
Containerless solidification of acoustically levitated Ni-Sn eutectic alloy
,”
Appl. Phys. A
109
,
239
(
2012
).
10.
E. H.
Trinh
and
C. J.
Hsu
, “
Equilibrium shapes of acoustically levitated drops
,”
J. Acoust. Soc. Am.
79
,
1335
(
1986
).
11.
C. P.
Lee
,
A. V.
Anilkumar
, and
T. G.
Wang
, “
Static shape and instability of an acoustically levitated liquid drop
,”
Phys. Fluids A
3
,
2497
(
1991
).
12.
S. D.
Danilov
and
M. A.
Mironov
, “
Breakup of a droplet in a high-intensity sound field
,”
J. Acoust. Soc. Am.
92
,
2747
(
1992
).
13.
Y.
Tian
,
R. G.
Holt
, and
R. E.
Apfel
, “
Deformation and location of an acoustically levitated liquid drop
,”
J. Acoust. Soc. Am.
93
,
3096
(
1993
).
14.
A. V.
Anilkumar
,
C. P.
Lee
, and
T. G.
Wang
, “
Stability of an acoustically levitated and flattened drop: An experimental study
,”
Phys. Fluids A
5
,
2763
(
1993
).
15.
C. P.
Lee
,
A. V.
Anilkumar
, and
T. G.
Wang
, “
Static shape of an acoustically levitated drop with wave-drop interaction
,”
Phys. Fluids
6
,
3554
(
1994
).
16.
B.
Pathak
and
S.
Basu
, “
Phenomenology of break-up modes in contact free externally heated nanoparticle laden fuel droplets
,”
Phys. Fluids
28
,
123302
(
2016
).
17.
M. A. B.
Andrade
and
A.
Marzo
, “
Numerical and experimental investigation of the stability of a drop in a single-axis acoustic levitator
,”
Phys. Fluids
31
,
117101
(
2019
).
18.
Y.
Wei
,
Y.
Yang
,
J.
Zhang
,
S.
Deng
,
S.
Liu
,
C. K.
Law
, and
A.
Saha
, “
Atomization of acoustically levitated droplet exposed to hot gases
,”
Appl. Phys. Lett.
116
,
044101
(
2020
).
19.
K.
Aoki
and
K.
Hasegawa
, “
Acoustically induced breakup of levitated droplets
,”
AIP Adv.
10
,
055115
(
2020
).
20.
Y.
Yamamoto
,
Y.
Abe
,
A.
Fujiwara
,
K.
Hasegawa
, and
K.
Aoki
, “
Internal flow of acoustically levitated droplet
,”
Microgravity Sci. Technol.
20
,
277
(
2008
).
21.
K.
Hasegawa
,
Y.
Abe
,
A.
Fujiwara
,
Y.
Yamamoto
, and
K.
Aoki
, “
External flow of an acoustically levitated droplet
,”
Microgravity Sci. Technol.
20
,
261
(
2008
).
22.
K.
Hasegawa
,
Y.
Abe
,
A.
Kaneko
,
Y.
Yamamoto
, and
K.
Aoki
, “
Visualization measurement of streaming flows associated with a single-acoustic levitator
,”
Microgravity Sci. Technol.
21
,
9
(
2009
).
23.
K.
Hasegawa
,
Y.
Abe
,
A.
Kaneko
, and
K.
Aoki
, “
PIV measurement of internal and external flow of an acoustically levitated droplet
,”
Int. J. Transp. Phenom.
12
,
151
(
2011
).
24.
A.
Goda
,
K.
Hasegawa
,
A.
Kaneko
,
T.
Kanagawa
, and
Y.
Abe
, “
External flow structure and interfacial transport phenomena of an acoustically levitated droplet
,”
Jpn. J. Multiphase Flow
28
,
539
(
2015
).
25.
K.
Kobayashi
,
A.
Goda
,
K.
Hasegawa
, and
Y.
Abe
, “
Flow structure and evaporation behavior of an acoustically levitated droplet
,”
Phys. Fluids
30
,
082105
(
2018
).
26.
Y.
Sasaki
,
K.
Kobayashi
,
K.
Hasegawa
,
A.
Kaneko
, and
Y.
Abe
, “
Transition of flow field of acoustically levitated droplets with evaporation
,”
Phys. Fluids
31
,
102109
(
2019
).
27.
K.
Hasegawa
,
A.
Watanabe
,
A.
Kaneko
, and
Y.
Abe
, “
Internal flow during mixing induced in acoustically levitated droplets by mode oscillations
,”
Phys. Fluids
31
,
112101
(
2019
).
28.
M.
Kawakami
,
Y.
Abe
,
A.
Kaneko
,
Y.
Yamamoto
, and
K.
Hasegawa
, “
Effect of temperature change on interfacial behavior of an acoustically levitated droplet
,”
Microgravity Sci. Technol.
22
,
145
(
2010
).
29.
M.
Kawakami
,
Y.
Abe
,
A.
Kaneko
, and
K.
Hasegawa
, “
Effect of laser heating on nonlinear surface deformation of acoustically levitated droplet
,”
Microgravity Sci. Technol.
22
,
353
(
2010
).
30.
K.
Hasegawa
,
Y.
Abe
, and
A.
Goda
, “
Microlayered flow structure around an acoustically levitated droplet under a phase-change process
,”
npj Microgravity
2
,
16004
(
2016
).
31.
B.
Al Zaitone
, “
Oblate spheroidal droplet evaporation in an acoustic levitator
,”
Int. J. Heat Mass Transfer
126
,
164
(
2018
).
32.
Y.
Niimura
and
K.
Hasegawa
, “
Evaporation of droplet in mid-air: Pure and binary droplets in single-axis acoustic levitator
,”
PLoS One
14
,
e0212074
(
2019
).
33.
Y.
Maruyama
and
K.
Hasegawa
, “
Evaporation and drying kinetics of water-NaCl droplets via acoustic levitation
,”
RSC Adv.
10
,
1870
(
2020
).
34.
M.
Junk
,
J.
Hinrichs
,
F.
Polt
,
J.
Fechner
, and
W.
Pauer
, “
Quantitative experimental determination of evaporation influencing factors in single droplet levitation
,”
Int. J. Heat Mass Transfer
149
,
119507
(
2020
).
35.
Y.
Sasaki
,
K.
Hasegawa
,
A.
Kaneko
, and
Y.
Abe
, “
Heat and mass transfer characteristics of binary droplets in acoustic levitation
,”
Phys. Fluids
32
,
072102
(
2020
).
36.
L. V.
King
, “
On the acoustic radiation pressure on spheres
,”
Proc. R. Soc. London, Ser. A
147
,
212
(
1934
).
37.
G.
Barrios
and
R.
Rechtman
, “
Dynamics of an acoustically levitated particle using the lattice Boltzmann method
,”
J. Fluid Mech.
596
,
191
(
2008
).
38.
D.
Foresti
,
M.
Nabavi
, and
D.
Poulikakos
, “
On the acoustic levitation stability behaviour of spherical and ellipsoidal particles
,”
J. Fluid. Mech.
709
,
581
(
2012
).
39.
Y.
Wada
,
K.
Yuge
,
R.
Nakamura
,
H.
Tanaka
, and
K.
Nakamura
, “
Dynamic analysis of ultrasonically levitated droplet with moving particle semi-implicit and distributed point source method
,”
Jpn. J. Appl. Phys.
54
,
07HE04
(
2015
).
40.
K.
Hasegawa
and
K.
Kono
, “
Oscillation characteristics of levitated sample in resonant acoustic field
,”
AIP Adv.
9
,
035313
(
2019
).
41.
D.
Zang
,
L.
Li
,
W.
Di
,
Z.
Zhang
,
C.
Ding
,
Z.
Chen
,
W.
Shen
,
B. P.
Binks
, and
X.
Geng
, “
Inducing drop to bubble transformation via resonance in ultrasound
,”
Nat. Commun.
9
,
3546
(
2018
).
42.
W.
Di
,
Z.
Zhang
,
L.
Li
,
K.
Lin
,
J.
Li
,
X.
Li
,
B. P.
Binks
,
X.
Chen
, and
D.
Zang
, “
Shape evolution and bubble formation of acoustically levitated drops
,”
Phys. Rev. Fluids
3
,
103606
(
2018
).
43.
A.
Marzo
,
S. A.
Seah
,
B. W.
Drinkwater
,
D. R.
Sahoo
,
B.
Long
, and
S.
Subramanian
, “
Holographic acoustic elements for manipulation of levitated objects
,”
Nat. Commun.
6
,
8661
(
2015
).
44.
T.
Hoshi
,
Y.
Ochiai
, and
J.
Rekimoto
, “
Three-dimensional noncontact manipulation by opposite ultrasonic phased arrays
,”
Jpn. J. Appl. Phys.
53
,
07KE07
(
2014
).
45.
A.
Watanabe
,
K.
Hasegawa
, and
Y.
Abe
, “
Contactless fluid manipulation in air: Droplet coalescence and active mixing by acoustic levitation
,”
Sci. Rep.
8
,
10221
(
2018
).
46.
K.
Hasegawa
,
A.
Watanabe
, and
Y.
Abe
, “
Acoustic manipulation of droplets under reduced gravity
,”
Sci. Rep.
9
,
16603
(
2019
).
47.
M. A. B.
Andrade
,
T. S. A.
Camargo
, and
A.
Marzo
, “
Automatic contactless injection, transportation, merging, and ejection of droplets with a multifocal point acoustic levitator
,”
Rev. Sci. Instrum.
89
,
125105
(
2018
).
48.
K.
Hasegawa
,
A.
Watanabe
,
A.
Kaneko
, and
Y.
Abe
, “
Coalescence dynamics of acoustically levitated droplets
,”
Micromachine
11
,
343
(
2020
).
49.
K.
Hasegawa
,
A.
Watanabe
,
A.
Kaneko
, and
Y.
Abe
, “
Feasibility study of droplet transportation via ultrasonic phased array system
,”
Int. J. Microgravity Sci. Appl.
37
,
370203
(
2020
).
50.
A.
Marzo
,
A.
Barnes
,
B. W.
Drinkwater
, and
TinyLev
, “
TinyLev: A multi-emitter single-axis acoustic levitator
,”
Rev. Sci. Instrum.
88
,
085105
(
2017
).
51.
The Japan Society of Mechanical Engineers (JSME)
,
JSME Data Book: Thermophysical Properties of Fluids
(
JSME
,
1983
).
52.
S.
Basu
,
A.
Saha
, and
R.
Kumar
, “
Thermally induced secondary atomization of droplet in an acoustic field
,”
Appl. Phys. Lett.
100
,
054101
(
2012
).
53.
S.
Basu
,
A.
Saha
, and
R.
Kumar
, “
Criteria for thermally induced atomization and catastrophic breakup of acoustically levitated droplet
,”
Int. J. Heat Mass Transfer
59
,
316
(
2013
).
54.
Q.
Shi
,
W.
Di
,
D.
Dong
,
L. W.
Yap
,
L.
Li
,
D.
Zang
, and
W.
Cheng
, “
A general approach to free-standing nanoassemblies via acoustic levitation self-assembly
,”
ACS Nano
13
,
5243
(
2019
).
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