Download PRELIMINARY STUDY ON PHOTONIC CRYSTAL

PRELIMINARY STUDY ON PHOTONIC CRYSTAL-BASED EUPHOLUS
CHEVROLATI BEETLE WING FOR REFRACTIVE INDEX SENSOR
Affi Nur Hidayah and Isnaeni
Research Center for Physics, Indonesian Institute of Sciences
Kawasan Puspiptek Serpong, Tangerang Selatan, Banten, 15310, Indonesia
Email: [email protected], [email protected]
Received:
Accepted:
ABSTRACT
Micro and nanostructures from nature are very interesting for research and applicable
technologies. One of the interesting structures is beetle wing since they have unique optical
properties. In this work, we have investigated morphology of nano and micro structure of beetle
wing from Eupholus Chevrolati species. We found that Eupholus Chevrolati beetle wing species
has perfect arrangement of nanostructure, known as photonic crystal structure. This kind of
structure is very interesting due to its high reflectance at particular wavelength corresponding to
its lattice structure. The result of SEM revealed three dimensional structure of photonic crystal
structure exhibited inside Eupholus Chevrolati beetle wing species. Beetle wing have rigid and
solid texture, so that applicable for optical devices applications. Finally, we have conducted
preliminary experiment to utilize Eupholus Chevrolati beetle wings species for refractive index
sensor. Ambiguos result! What are they????
Keywords: photonic crystal, beetle wing, Eupholus Chevrolati
ABSTRAK
Struktur yang berasal dari alam sangatlah menarik untuk diteliti dan dikembangkan menjadi
sebuah teknologi. Salah satu struktur yang menarik dan memiliki sifat optik yang unik adalah
sayap kumbang. Dalam penelitian ini dilakukan kajian tentang struktur sayap kumbang dari
spesies Eupholus Chevrolati. Hasil SEM menunjukkan bahwa struktur sayap kumbang tersebut
memiliki struktur kristal fotonik. Struktur kristal fotonik sangatlah menarik karena memiliki
tingkat refleksifitas yang khas dan diketahui bahwa sayap kumbang Eupholus Chevrolati
memiliki struktur kristal fotonik tiga dimensi. Sayap kumbang ini memiliki tekstur yang cukup
kuat sehingga dapat diaplikasi dalam aplikasi teknologi. Dan telah dilakukan pengujian indeks
bias air dengan menggunakan sayap kumbang sebagai sensor. Hasil penelitian ini dapat
dikembangkan lebih lanjut agar sayap kumbang ini dapat diterapkan sebagai divais fotonik.
Kata kunci: Kristal fotonik, sayap kumbang, Eupholus Chevrolati
INTRODUCTION
Biodiversities and animals in Indonesia have been recognized internationally. However their use
is very limited, especially in the world of science and technology. Nowadays, the development of
world science and technology begin to shift in the direction of research and utilization of the
natural structure of animals and plants. In the field of optics, there are a lot of structures of
animals and plants that can be used or replicated to be developed into a high-level technologies.
Technology that utilizes the natural structure is usually referred to as bio-inspiring technology
[1]. For example, the structure and shape of honey is hexagonal structure which is the most
efficient and powerful than other structures, so that this structure has been utilized in the field of
technology of building structures [2]. Another example is the wing of butterflies and some
insects interesting color ranging from blue to red color have a distinctive structure called
photonic crystal [3-5].
It is well known that the photonic crystal structure is special structure that can reflect
certain wavelength that corresponds to dimension and spacing crystal lattice [4-5]. Photonic
crystals are material whose structure consists of two types of materials with different refractive
indices arranged regularly. The array of the two materials can be in the form of one, two or three
dimensions [6]. Photonic crystal structures are shown with vivid color in nature and found in
species of birds, butterflies, insects, marine animals and plants. One-dimensional (1D) photonic
crystal structure found in insects, birds, fish, leaves and berries are indicated with multilayer
structures. While the two-dimensional photonic crystal (2D) contained in peacock feathers and
polychatae worms has more complex color structure and shaped diffraction gratings. Threedimensional photonic crystal (3D) found in some types of beetles and butterflies. 3D photonic
crystal capable of reflecting the color with wider angle outreach and shaped like a matrix that
contains layers that are stacked in a hexagonal [7]. In the world of optics, photonic crystal is very
useful, especially for nanophotonics technology. One of the interesting application of photonic
crystal is as a optical sensor [10-12].
One of the hollow photonic crystal useful is photonic crystal from beetle wing on
Eupholus Chevrolati. This beetle belongs to the Family Curculionidae and the color is green
metallic bluish. The beetle can reach a length of 25 mm and mostly found in the tropics,
especially in Indonesia. Previous research showed that the color of beetle wing is not purely
derived from certain pigment [8-9].
For the introduction, It is not clear what is the aim of this paper?
METHODOLOGY
This research uses the beetle wing of Eupholus Chevrolati obtained from Insect Museum and
Butterfly Park, Taman Mini Indonesia Indah, Jakarta, Indonesia. Experiment was done by
observing: (1) micro and nano structures beetle wing, (2) The reflection spectrum, and (3)
changes in the reflection spectrum due to changes in the refractive index. Microstructure
observation beetle wing was done by using microscope that has camera recorder with 100X and
400x magnification, and Scanning Electron Microscope (SEM) to determine the morphology of
the wing structure. Measurement of reflection spectrum is done with magnification 100X
microscope equipped with USB-HR 2000 spectrophotometers from Ocean Optics, as seen
picture 1. ???? The halogen lamp used as a light source, is positioned to form 45o to beetle wing
sample. This angle was chosen to test the reflection spectrum, because this angle gives the
highest intensity and matching settings of sample and easy to use microscope. Reflection
spectrum is recorded by spectrophotometers by comparing the reflection spectrum without beetle
wing (as a reference spectrum) to the reflection spectrum of the beetle wing. Beetle wing
measurement to observe the refractive index is done by soaking beetle wing in water solvent and
test the reflection spectrum.
Figure 1. Set-up test reflection spectrum of the beetle wing of Eupholus Chevrolati
RESULTS AND DISCUSSION
The beetle wing color of Eupholus Chevrolati is metallic bluish green. The color of the beetle is
spread throughout the body, including the legs, arms, head and specially the body as shown in
Figure 2a. The green color punctuated by black color with a distinctive pattern on the body. In
this study, the black part on the beetle does not have photonic crystal structure. Beetle wing
section that has metallic green color is the part of beetle wing that has photonic crystal structure
and the focus of this study. Metallic green bluish color on the surface of the body of the
Eupholus Chevrolati beetle species comes from small pieces that attach to the entire body of the
beetle, as shown in Figure 2b. The green pieces are visible well under a microscope with a
magnification 100X or 400X. Each fragment is flat round shape with a diameter ranging between
30m to 40m. From the observation using microscope, the surface of the each fragment piece is
not smooth. Surface fragment beetle wing consist of segments where the visible color of each
segment is slightly different from the surrounding segments. Some surface-colored segments
tend to be more blue??? than the body that are not covered by colored pieces. Overall, the whole
body is covered by a beetle colored pieces as shown in Figure 2a. It is known that each piece is
coated by a layer of wax which cause metallic colors can be seen. Wax coating also keep the
inside pieces so as not to become brittle and crumble.
Figure 2. The Eupholus Chevrolati beetle species (a) and magnification 100X of fragment of
wing with microscope (b)
To find out more detailed structure contained in each fragment, carried out test on the
body of the beetle with SEM, as shown in Figure 3. In this figure, it appears that the beetle’s
body surface is covered by fragments with a dimeter of between 30m to 40m. The
measurement of size fragment between SEM and microscope is little different. This is due to
enlargement and less precise calibration scale on the microscope. From the SEM images, it was
clear that the surface of each fragment is quite smooth and not bumpy or segmented as
previously predicted from the test results with microscope. This condition makes the question
why the surface of each fragment on microscope testing is segmented and colored little
different?. To answer this question, further measurement of a cross-section SEM on a fragment
of beetle wing as shown in Figure 3b. In the picture, it can be seen clearly that in every fragment
there is a thin layer, which is estimated as a layer of wax, which protects the inside of fragment.
The inside of the fragment neatly arranged to form a hollow structure that is organized and
almost perfect. This structure is very similar to the arrangement in the form woodpile photonic
crystal structure (pyre).
Magnification microscope used is 100X. First, three measurements were done at three
Further measurement of reflection spectra on beetle wing is done with the equipment as
shown in Figure 1. different positions beetle wing as seen in Figure 4. This figure shows that the
reflection spectra for three wings positions. All spectrum have nearly the same shape, and it is
also almost the same spectrum peak at wavelength of 485 nm. There is slight difference in the
peak intensity of reflection spectrum, because the average thickness of the tested beetle wing is
not same. So there was a slight difference in intensity.
Figure 4. Reflection spectrum of beetle wing in three different positions
It is not clear, where the position of wings 1,2 and 3 are taken???? And no scientific
explanation why they are different???
The structure contained in the fragment beetle wing is hollow photonic crystal structure,
wherein the structure of the cavity is filled by air. If cavities in the structure filled with water or
other solution, then the ratio of the refractive index in the photonic crystal will change, so this
will result in changes in the reflection spectrum. Based on this, the testing has been carried out
when the reflection spectrum beetle wing soaked or put in the water, as shown in Figure 5. The
experimental results show that the intensity of the reflection spectrum shifts from 485 nm when
the photonic crystal cavity containing air, to 505 nm while photonic crystal cavity containing
water.
Figure 5. Reflection spectrum beetle wing in air and water
Which one of the wing’s part that is shown in Fig. 5???
And how abot if it tested in other transparent objects?
Photonic crystal can reflect particular wavelength represent crystal lattice, this is due to
regular structure of two materials produce photonic pass band. Photonic pass band or forbidden
wavelength (gap) make particular wavelength can’t be transmitted. Photonic crystal lattices
affect reflexivity in accordance
with equation [6].
(1)
where n is refractive index, d is thickness of the material and index 1 and 2 is compiler material.
In the picture 5, the value of the wavelength of the reflection spectrum is the forbidden
wavelength (λgap) resulted from photonic pass band in photonic crystal. The photonic pass band
in the photonic crystals hinders wavelength on the refractive index material transmitted. On a
photonic crystal, there are several layers and interfaces of materials. If any wave reflection by all
interfaces have phase (phase) the same wavelength, then the photonic crystal structure reflect
specific wavelengths perfectly. Wave velocity and the phase of the wave is determined by the
type of material, one factor is the refractive index of the material making up the photonic crystal.
By replacing the constituent material photonic crystal with a material which has a refractive
index different then the reflected wavelength will be different.
Photonic crystal can be made with hollow material structure is perfect. In a photonic
crystal cavity can be filled with air (n = 1), water (n = 1,333), or other solutions. Perfect hollow
photonic crystal structure like this is very useful to be applied as the refractive index sensors or
other sensors.
Suppose that in the process of reflection spectrum measurement beetle wings in the air,
then the reflection wavelength of the refractive index of air is not transmitted but reflected, so
that the reflected wavelength captured by spectrophotometers. Likewise at the time of
measurement of the refractive index of water, the reflection spectrum of wavelengths which is
the value of the refractive index of water are only reflected. Reflection wavelength spectrum
resulted from the halogen lamp sources that emit photon, photon falling on 3D photonic crystal
cavity having a forbidden photonic band pass, the photonic crystal cavity filled with air or water
or other materials, then the photon is reflected and transmitted, only photons with a wavelength
corresponding to the value of the refractive index of the crystal cavity fillers (eg, air, water) are
reflected and read by spectrophotometer.
With the acquisition value of the wavelength of the reflection spectrum intensity (λgap)
from beetle wing in the air and in the water, the value of the refractive index of air or water (n)
can be obtained by using equation 1 (𝑔𝑎𝑝 = 2 (𝑛1 𝑑1 + 𝑛2 𝑑2 )). For further, fragments of the
beetle wing can be tried to test other solvent refractive index with the same principles that is put
fragments of beetle wing into the solvent researching and seek wavelength intensity value of the
reflection spectrum of beetle wing on the solvent.
In Figure 5, a wavelength shift of approximately 20 nm as far as this is an excellent
starting clue for the application of beetle wings into biological sensors, in this case the refractive
index sensors. From the pictures it is shown that the intensity of the reflection spectrum of beetle
wings in water is lower than the intensity of the reflection spectrum beetle wing in the air. This
difference is an indication that the beetle wing capable of being a candidate of refractive index
sensor based on optical sensor.
CONCLUSION
Optical characterization has been done to the Eupholus Chevrolati beetle wing. From testing
microscope and SEM seen that almost the entire surface of the beetle's body is covered by small
fragments measuring under 40m. Each fragment produces a metallic green color which is a
bluish light reflection due to hollow photonic crystal structure contained in each fragment.
Photonic crystal structure in every fragment of very regular and almost perfect, but not homogen
crystal structure, so there is a slight difference in color on every fragments. Further, the reflection
spectra have been measured and beetle wing produce a distinctive spectrum. There are
differences in the peak wavelength of the reflection spectrum between beetle wing in the air and
beetle wing in water far more than 20m.( this sentence should be included in the abstract!!)
This difference is very beneficial for the beetle wing as it can be used as bio-sensors, particularly
sensors of refractive index.
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Gerneral Cooments: In general ok to be accepted to be published after some additional
correction, such as:
1.English should be improved, grammatical errors throughout the manuscript
2.Need deeper analysis on the results.
3.Pay attention to the comments on the text.