This article recounts a scientific investigation that started from the observation of an ordinary everyday phenomenon. In a cup of tea, dipping buttered toast produces on the surface of the tea beautifully evolving lenses, which are pierced repeatedly by moving holes. To unravel this dynamic observation, we show here how we simplified the system into its basic ingredients, and how we excluded several hypotheses such as thermal convection. We reproduce the phenomenon with an inverse emulsion of surfactant-laden water droplets. Depending on the spreading of the lens, we also observe and explain the formation of an oil lacework and “swimming” lenses.
REFERENCES
1.
L.
Leger
and
J. F.
Joanny
, “
Liquid spreading
,” Rep. Prog. Phys.
55
, 431
–486
(1992
).2.
Daniel
Bonn
,
Jens
Eggers
,
Joseph
Indekeu
,
Jacques
Meunier
, and
Etienne
Rolley
, “
Wetting and spreading
,” Rev. Mod. Phys.
81
, 739
–805
(2009
).3.
Jacco H.
Snoeijer
and
Bruno
Andreotti
, “
Moving contact lines: Scales, regimes, and dynamical transitions
,” Ann. Rev. Fluid Mech.
45
, 269
–292
(2013
).4.
G.
Bobe
,
S.
Zimmerman
,
E. G.
Hammond
,
A. E.
Freeman
,
P. A.
Porter
,
C. M.
Luhman
, and
D. C.
Beitz
, “
Butter composition and texture from cows with different milk fatty acid compositions fed fish oil or roasted soybeans
,” J. Dairy Sci.
90
, 2596
– 2603
(2007
).5.
A. C.
Juriaanse
and
I.
Heertje
, “
Microstructure of shortenings, margarine and butter-a review
,” Food Struct.
7
, 181
–188
(1988
), see https://digitalcommons.usu.edu/foodmicrostructure/vol7/iss2/8.6.
Rodrigo Leite
Pinto
,
Sébastien
Le Roux
,
Isabelle
Cantat
, and
Arnaud
Saint-Jalmes
, “
Enhanced interfacial deformation in a Marangoni flow: A measure of the dynamical surface tension
,” Phys. Rev. Fluids
3
, 024003
(2018
).7.
M. C.
Wilkinson
, “
Extended use of, and comments on, the drop-weight (drop-volume) technique for the determination of surface and interfacial tensions
,” J. Colloid Interface Sci.
40
, 14
–26
(1972
).8.
Matthieu
Roché
,
Zhenzhen
Li
,
Ian M.
Griffiths
,
Sébastien Le
Roux
,
Isabelle
Cantat
,
Arnaud
Saint-Jalmes
, and
Howard A.
Stone
, “
Marangoni flow of soluble amphiphiles
,” Phys. Rev. Lett.
112
, 208302
(2014
).9.
Sébastien
Le Roux
, “
Marangoni effect at fluid interfaces
,” Ph.D. thesis, Université Rennes 1 (2015
).10.
Roman
Stocker
and
John W. M.
Bush
, “
Spontaneous oscillations of a sessile lens
,” J. Fluid Mech.
583
, 465
–475
(2007
).11.
L.
Keiser
,
H.
Bense
,
P.
Colinet
,
J.
Bico
, and
E.
Reyssat
, “
Marangoni bursting: Evaporation-induced emulsification of binary mixtures on a liquid layer
,” Phys. Rev. Lett.
118
, 074504
(2017
).12.
F.
Wodlei
,
J.
Sebilleau
,
J.
Magnaudet
, and
V.
Pimienta
, “
Marangoni-driven flower-like patterning of an evaporating drop spreading on a liquid substrate
,” Nat. Commun.
9
, 820
(2018
).13.
Yong-Jun
Chen
,
Yuko
Nagamine
, and
Kenichi
Yoshikawa
, “
Self-propelled motion of a droplet induced by Marangoni-driven spreading
,” Phys. Rev. E
80
, 016303
(2009
).14.
Ziane
Izri
,
Marjolein N.
van der Linden
,
Sébastien
Michelin
, and
Olivier
Dauchot
, “
Self-propulsion of pure water droplets by spontaneous Marangoni-stress-driven motion
,” Phys. Rev. Lett.
113
, 248302
(2014
).15.
A.
Girot
,
N.
Danné
,
A.
Würger
,
T.
Bickel
,
F.
Ren
,
J. C.
Loudet
, and
B.
Pouligny
, “
Motion of optically heated spheres at the water–air interface
,” Langmuir
32
, 2687
–2697
(2016
).16.
Charles
Tomlinson
and
Allen
Miller
, “
On the motions of camphor on the surface of water
,” Proc. R. Soc. London
11
, 575
–577
(1862
).17.
Satoshi
Nakata
,
Masaharu
Nagayama
,
Hiroyuki
Kitahata
,
Nobuhiko J.
Suematsu
, and
Takeshi
Hasegawa
, “
Physicochemical design and analysis of self-propelled objects that are characteristically sensitive to environments
,” Phys. Chem. Chem. Phys.
17
, 10326
–10338
(2015
).18.
Ronan
Kervil
, “
Active matter and flows: Bacterial jets and interfacial swimmers
,” Ph.D. thesis, Université de Lyon (2018
).19.
See Supplementary Material at https://doi.org/10.1119/10.0000025 for Supplementary Movies 1–5.
© 2019 American Association of Physics Teachers.
2019
American Association of Physics Teachers
AAPT members receive access to the American Journal of Physics and The Physics Teacher as a member benefit. To learn more about this member benefit and becoming an AAPT member, visit the Joining AAPT page.
