The flexibility of insect wings confers aerodynamic benefits, but can also present a hazard if exposed to fog or dew. Fog can cause water to accumulate on wings, bending them into tight taco shapes and rendering them useless for flight. In this combined experimental and theoretical study, we use high-speed video to film the spontaneous folding of isolated mosquito wings due to the evaporation of a water drop. We predict shapes of the deformed wing using two-dimensional elastica theory, considering both surface tension and Laplace pressure. We also recommend fold-resistant geometries for the wings of flapping micro-aerial vehicles. Our work reveals the mechanism of insect wing folding and provides a framework for further study of capillarity-driven folding in both natural and biomimetic systems at small scales.
REFERENCES
1.
G. S.
Watson
, B. W.
Cribb
, and J. A.
Watson
, “Contrasting micro/nano architecture on termite wings: Two divergent strategies for optimising success of colonisation flights
,” PLoS One
6
, e24368
(2011
).2.
A. K.
Dickerson
and D. L.
Hu
, “Mosquitoes actively remove drops deposited by fog and dew
,” Integr. Comp. Biol.
42
, 1
–6
(2014
).3.
A.
Dickerson
, P.
Shankles
, N.
Madhavan
, and D.
Hu
, “Mosquitoes survive raindrop collisions by virtue of their low mass
,” Proc. Natl. Acad. Sci.
109
, 9822
–9827
(2012
).4.
A. K.
Dickerson
, P. G.
Shankles
, and D. L.
Hu
, “Raindrops push and splash flying insects
,” Phys. Fluids
26
, 027104
(2014
).5.
R.
Wood
, “The first takeoff of a biologically inspired at-scale robotic insect
,” IEEE Trans. Rob.
24
, 341
–347
(2008
).6.
P.
Zdunich
, D.
Bilyk
, M.
MacMaster
, D.
Loewen
, J.
DeLaurier
, R.
Kornbluh
, T.
Low
, S.
Stanford
, and D.
Holeman
, “Development and testing of the mentor flapping-wing micro air vehicle
,” J. Aircr.
44
, 1701
–1711
(2007
).7.
F.
Van Breugel
, Z.
Teoh
, and H.
Lipson
, “A passively stable hovering flapping micro-air vehicle
,” in Flying Insects and Robots
(Springer
, 2009
), pp. 171
–184
.8.
M.
Groen
, B.
Bruggeman
, B.
Remes
, R.
Ruijsink
, B.
Van Oudheusden
, and H.
Bijl
, “Improving flight performance of the flapping wing MAV delfly ii
,” in International Micro Air Vehicle Conference and Flight Competition
(Delft University of Technology, Braunschweig, Germany
, 2010
).9.
G.
De Croon
, K.
De Clercq
, R.
Ruijsink
, B.
Remes
, and C.
De Wagter
, “Design, aerodynamics, and vision-based control of the DelFly
,” Int. J. Micro Air Veh.
1
, 71
–97
(2009
).10.
C.
Py
, P.
Reverdy
, L.
Doppler
, J.
Bico
, B.
Roman
, and C.
Baroud
, “Capillary origami: Spontaneous wrapping of a droplet with an elastic sheet
,” Phys. Rev. Lett.
98
, 156103
(2007
).11.
A.
Fargette
, S.
Neukirch
, and A.
Antkowiak
, “Elastocapillary snapping: Capillarity induces snap-through instabilities in small elastic beams
,” Phys. Rev. Lett.
112
, 137802
(2014
).12.
J.
van Honschoten
, J.
Berenschot
, R.
Sanders
, L.
Abelmann
, N.
Tas
, and M.
Elwenspoek
, “Fabrication of three-dimensional microstructures using capillary forces
,” in Proceedings of the 20th Micromechanics Europe Workshop
, (MME 09
) (Laas-CNRS
, Toulouse, France
, 2009
), pp. 1
–4
.13.
M.
Boncheva
, D. A.
Bruzewicz
, and G. M.
Whitesides
, “Millimeter-scale self-assembly and its applications
,” Pure Appl. Chem.
75
, 621
–630
(2003
).14.
S.
Jung
, P.
Reis
, J.
James
, C.
Clanet
, and J.
Bush
, “Capillary origami in nature
,” Phys. Fluids
21
, 91
–110
(2009
).15.
J.
Braam
, “In touch: Plant responses to mechanical stimuli
,” New Phytol.
165
, 373
–389
(2005
).16.
W. M.
Forbes
, “How a beetle folds its wings
,” Psyche
31
, 254
–258
(1924
).17.
F.
Haas
and R. G.
Beutel
, “Wing folding and the functional morphology of the wing base in coleoptera
,” Zoology
104
, 123
–141
(2001
).18.
Y.
Zheng
, X.
Gao
, and L.
Jiang
, “Directional adhesion of superhydrophobic butterfly wings
,” Soft Matter
3
, 178
–182
(2007
).19.
T.
Wagner
, C.
Neinhuis
, and W.
Barthlott
, “Wettability and contaminability of insect wings as a function of their surface sculptures
,” Acta Zool.
77
, 213
–225
(1996
).20.
S. H. T.
Nguyen
, H. K.
Webb
, J.
Hasan
, M. J.
Tobin
, R. J.
Crawford
, and E. P.
Ivanova
, “Dual role of outer epicuticular lipids in determining the wettability of dragonfly wings
,” Colloids Surf., B
106
, 126
–134
(2013
).21.
D.
Byun
, J.
Hong
, J. H.
Ko
, Y. J.
Lee
, H. C.
Park
, B.-K.
Byun
, and J. R.
Lukes
, “Wetting characteristics of insect wing surfaces
,” J. Bionic Eng.
6
, 63
–70
(2009
).22.
M.
Sun
, G. S.
Watson
, Y.
Zheng
, J. A.
Watson
, and A.
Liang
, “Wetting properties on nanostructured surfaces of cicada wings
,” J. Exp. Biol.
212
, 3148
–3155
(2009
).23.
J.
Jopp
, H.
Grüll
, and R.
Yerushalmi-Rozen
, “Wetting behavior of water droplets on hydrophobic microtextures of comparable size
,” Langmuir
20
, 10015
–10019
(2004
).24.
T.
Yu
, J.
Park
, H.
Lim
, and K.
Breuer
, “Fog deposition and accumulation on smooth and textured hydrophobic surfaces
,” Langmuir
28
, 12771
–12778
(2012
).25.
J. W. M.
Bush
, D. L.
Hu
, and M.
Prakash
, “The integument of water-walking arthropods: Form and function
,” in Insect Mechanics and Control: Advances in Insect Physiology
(Elsevier
, 2007
), Vol. 176
, pp. 117
–192
.26.
A. M.
Mountcastle
and S. A.
Combes
, “Wing flexibility enhances load-lifting capacity in bumblebees
,” Proc. R. Soc. B
280
(2013
).27.
J.
Gosline
, M.
Lillie
, E.
Carrington
, P.
Guerette
, C.
Ortlepp
, and K.
Savage
, “Elastic proteins: Biological roles and mechanical properties
,” Philos. Trans. R. Soc., B
357
, 121
–132
(2002
).28.
F.-O.
Lehmann
, S.
Gorb
, N.
Nasir
, and P.
Schützner
, “Elastic deformation and energy loss of flapping fly wings
,” J. Exp. Biol.
214
, 2949
–2961
(2011
).29.
S. N.
Gorb
, “Serial elastic elements in the damselfly wing: Mobile vein joints contain resilin
,” Naturwissenschaften
86
, 552
–555
(1999
).30.
S.
Combes
and T.
Daniel
, “Flexural stiffness in insect wings ii. Spatial distribution and dynamic wing bending
,” J. Exp. Biol.
206
, 2989
–2997
(2003
).31.
A. B.
Kesel
, U.
Philippi
, and W.
Nachtigall
, “Biomechanical aspects of the insect wing: An analysis using the finite element method
,” Comput. Biol. Med.
28
, 423
–437
(1998
).32.
S.
Combes
and T.
Daniel
, “Flexural stiffness in insect wings I. Scaling and the influence of wing venation
,” J. Exp. Biol.
206
, 2979
–2987
(2003
).33.
See supplementary material at http://dx.doi.org/10.1063/1.4908261 for folding videos. Video S1shows folding sequences of a mosquito, fruit fly, and house fly wings, respectively, upon exposure to a fog stream. Folding generally occurs chordwise, tending to make the wings into hot-dogs.Video S2 show a drop evaporating from the tip of two mosquito wings. Upon evaporation, the first wing closes more tightly, while the second returns to its natural shape.
34.
L.
Johnson
and D.
Scholz
, “On Steffensen’s method
,” SIAM J. Numer. Anal.
5
, 296
–302
(1968
).35.
J.
Shang
, S.
Combes
, B.
Finio
, and R.
Wood
, “Artificial insect wings of diverse morphology for flapping-wing micro air vehicles
,” Bioinspiration Biomimetics
4
, 1
–6
(2009
).36.
S.
Neukirch
, A.
Antkowiak
, and J.-J.
Marigo
, “The bending of an elastic beam by a liquid drop: A variational approach
,” Proc. R. Soc. A
(published online 2013). 37.
A.
Antkowiak
, B.
Audoly
, C.
Josserand
, S.
Neukirch
, and M.
Rivetti
, “Instant fabrication and selection of folded structures using drop impact
,” Proc. Natl. Acad. Sci.
108
, 10400
–10404
(2011
).© 2015 AIP Publishing LLC.
2015
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