World Journal of Engineering
MULTIPLE LEVELS, SCALES AND FUNCTIONS IN
MICRO/NANO STRUCTURES OF DRAGONFLY WING
VEINS
ZHAO Hongxiao 1, YIN YaJun 2, ZHONG Zheng 1
1 School of Aerospace Engineering and Applied Mechanics, Tongji University, 1239 Siping
Road, Shanghai 200092, China Email: zhongk@tongji.edu.cn
2 Department of Engineering Mechanics, School of Aerospace, Tsinghua University, Beijing
100084, China
Introduction
Many
researchers
have
studied
systematically the structures and
functions of dragonfly wings [1-2]. We
have also made some progresses in this
research field. We focused on the outer
surfaces of dragonfly wing veins [3] and
displayed randomly distributed micro/
nano wavelike ripples. We explored the
cross-section
of
pterostigma
of
dragonfly [4] and disclosed the
vessel-like structure with curved walls
and
revealed
the
composite
constructions of nano-fiber reinforced
multiple layers. We focused on the
conjunctive sites of the vein/ membrane/
spike [5] and found the smooth
transition mode and global package
assembly mode in the dragonfly wings.
In this paper, we will concentrate on the
internal micro/nano structures of
dragonfly wing veins.
Fig.1. The "map" for measured cross-section
of the veins
Results and Discussion
Fig.1 shows the detailed “map” for
observed locations and the photos of
cross sections, respectively.
The generalities and particularities in
the vein structures
In Fig.1, all veins are of tube-like
structures. But there are very large
differences between them. a) Their
geometric shapes are different: there are
curved-triangle cross-section, dumbbellshaped cross-section, etc; b) Different
structures: In the back-edge district and
the tip district at where loads are small,
the veins are thin bilayer tubes with
simpler structure (Fig.2). At the root
district and the front-edge district at
where loads are high, the veins are thick
multi-layer tubes with complicated
structures (Fig.3 (a), (b)).
The multiple levels and scales in the
structures of the Subcosta
From Fig.3b, we find that the upper
fractured section is a multi-layer
structure. There are four layers:
Materials and methods
The sample is the right forewing of a
Pantala flavescens Fabricius (Fig.1)
caught in the suburbs of Shanghai. First,
the sample is embedded by epoxy and
cured at room temperature for 24 hours
after fixed by 2.5% glutaraldehyde and
1% Osmium tetroxide. Second, it is
immersed in liquid nitrogen for 1~2 min,
taken out and broken to obtain brittle
fracture cross-sections of dragonflies
wings. Third, it is coated with gold
about 6nm thick. Finally it is observed
by using FEG-ESEM.
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World Journal of Engineering
condensed compaction of parallel nano
fibers. The thickness of the middle layer
is about 11μm. In Fig.3b, the cleavage
surfaces of the middle layer are of
fanwise morphologies. Inside the
fanwise morphologies there are fine
nano structures: condensed nano fibers
are compacted into nano layers, and the
nano layers are stacked into radiated
fanwise morphologies.
Fig.2. The cross-section of the longitudinal
vein at the back-edge marked 0.7L
Conclusion
The following conclusions may be made:
(a) Different cross-sections have
different micro/nano structures; (b) At
large scale, the structures of the veins
are of diversities and disorders. At small
scale, the structures of the veins are of
unifications and orders, which may be
termed the unified assembling mode, i.e.
the “nano fibers → nano layers” mode;
(c) The mechanical functions of the
micro/nano structures of the veins are
optimized synthetically. (d) The
profound mysteries in the dragonfly
wing veins provide valuable references
for bionics of aircrafts with small size
scales.
(a)
(b)
Fig.3 The brittle fracture sections of the
Subcosta marked 0.1L and the locally
magnified photo
References
1. WOOTTON, R. J., The functional
morphology of the wings of dragonflies. J.
Adv. Odonatol. 5(1991) 153–169.
2. WOOTTON, R. J., Herbert, R. C., Young,
P. G.and Evans, K. E. Approaches to the
structural modeling of insect wings. J. Phil.
Trans. R. Soc. Lond., B.358 (2003)1577–1587.
3. ZHAO, H.X., Yin, Y.J. and Zhong, Z.,
2010.Micro and nano structures and
morphologies on the wing veins of dragonflies.
Chinese Sci. Bull., 55(2010)1993−1995.
4. ZHAO, H.X., Yin, Y.J. and Zhong, Z. Nano
Fibrous
Multilayered
Composites
in
Pterostigma of Dragonfly. Chinese Sci. Bull.,
55(2010)1856-1858 (in Chinese)
5. ZHAO, H. X., Yin, Y.J. and Zhong, Z., 2011.
Assembly modes of dragonfly wings. Microsc.
Res. Tech., Accepted. (2011)
which are the inner layer, the middle
layer, the transition layer and the outer
layer. The outer layer is part of the
membranes. As for the transition layer,
its thickness is about 6μm. Its fracture
surface
shows
honeycomb-like
morphology. The inner layer is an
elliptical laminate composite shell
(Fig.3b) with 6 sub-layers and looks like
6 coaxial tubes connected closely
together. The thin shell is formed by the
continuous stacking of extremely thin
nano layers, and every nano layer is the
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