=Paper=
{{Paper
|id=Vol-1900/paper10
|storemode=property
|title=Microexplosions polysterene microparticles on substrate covered by aluminum
|pdfUrl=https://ceur-ws.org/Vol-1900/paper10.pdf
|volume=Vol-1900
|authors=Vadim S. Vasilev,Roman V. Skidanov
}}
==Microexplosions polysterene microparticles on substrate covered by aluminum==
https://ceur-ws.org/Vol-1900/paper10.pdf
Microexplosions polysterene microparticles on substrate covered by
aluminum
1,2 1,2
V.S. Vasilev , R.V. Skidanov
1
Samara National Research University, 34 Moskovskoe Shosse, 443086, Samara, Russia
2
Image Processing Systems Institute – Branch of the Federal Scientific Research Centre “Crystallography and Photonics” of Russian Academy of Sciences,
151 Molodogvardeyskaya st., 443001, Samara, Russia
Annotation
Experimental results of microexplosion polysterene microparticles diameter equals 5 micron located on substrate covered by aluminum layer
thickness in 100 nanometers were showed. Produced a comparison results of experiment on quartz substrate and on aluminum substrate. As a
source of radiation was chosen a laser with wavelength equals 355 nanometers.
Keywords: microexplosions; ultraviolet beam, polysterene microbits; velocity of microparticles; quartz substrate; aluminum substrate
1. Introduction
Currently, all manipulation works are now heading for reducing the size of the moving objects. There are plenty of
microparticles manipulation methods using optical traps of different types. However, it is desirable to have a method to move a
relatively large micro-objects. Especially such objects could be found in biological research (sporules, microslides of tissue,
large cells). And it is necessary to prevent an effect even of a minimum quantity of light radiation on the biological micro-object.
It is possible to carry out mechanical micro-manipulation by means of mechanical micro tweezers. This method is invasive for
microparticles manipulating.
Typical sizes of the roaming micro-objects using common optical trap are from fractions of a micrometer to about ten
micrometers. It is necessary to significantly increase the power of the light beam with the increase of the micro-objects size.
Because anyway some fraction of the light beam energy is absorbed by the object, there is a certain limit for the microparticles
size which can be moved by the forces of optical trapping. The precise value of this size depends on many parameters: the
micro-objects absorption coefficient, fluid properties, micro-object surface shape, etc. A rough estimate of this size for
transparent spherical micro-objects gives a value of about 30 µm. It should be noted that the micro-object with a size close to the
limit is experienced strong thermal impact. Things get worse with the movement of opaque micro-objects in the light traps. The
limiting size is reduced by one and a half to two times. At the same time, the micro-objects with sizes up to 100 microns are still
quite small for a mechanical movement. There is another complicate combined method of micro-objects grasping with the usage
of light and ultrasound [5]. But here is another [6] described simpler method of moving micro-objects by means of the
microexplosions of polystyrene microparticles in a beam of an ultraviolet laser with a wavelength of 355 nm.
In this paper we will consider a method of moving micro-objects with explosion of polystyrene microparticles on a substrate
coated with a layer of aluminium. As compared with microexplosions on a quartz substrate, this method significantly reduces
expended energy of microexplosions due to the interference of the beam, which is incident on the substrate and a beam reflected
from the surface of the substrate.Object of study in this research is calculation average velocity polysterene microparticles with
diameter equals 5 micron after microexplosion occurring under the pressure of laser emission with wavelength 355 nanometers.
The subject of the study is the behavior of polystyrene micro-particles in the explosion.
The aim of this work is the experimental test of interference effect between incident and reflected beams in the explosion on a
substrate covered with aluminum. Another aim of this work is the calculation of scattering speed of microparticles after the
explosion and finding the parameters for explosion occurrence.
In accordance with the intended aims following tasks were summarized:
in situ observation of polystyrene microparticles microexplosion on a substrate covered with aluminum under the action of
ultraviolet laser with a wavelength of 355 nm;
the calculation of the average dispersion velocity of polystyrene microparticles after the explosion;
finding the system parameters for the observed microexplosions of polystyrene microspheres.
Scientific and practical novelty and significance of the results:
full-scale experiment with the microexplosion of polystyrene microparticles on a substrate covered with aluminum under the
action of an ultraviolet laser with a wavelength of 355 nm was successfully completed.
the average expansion rate of polystyrene microparticles after microexplosion was calculated.
the system parameters for the observed polystyrene microspheres microexplosions were found.
2. Theoretical description observed effect
In this experiment, there is an effect of interference of incident and reflected waves. As a result of usage a single source of
light radiation the incident and reflected waves are coherent. Thus, the total intensity of incident and reflected waves [7] can be
represented as follows:
3rd International conference “Information Technology and Nanotechnology 2017” 48
Computer Optics and Nanophotonics / V.S. Vasilev, R.V. Skidanov
I I1 I 2 2 I1 I 2 cos (1)
where I1 , I 2 - the intensity of the incident and reflected beams, respectively, δ - the phase difference between these beams.
Considering that quartz glass has a transmittance of 99% and aluminum reflects about 93-94%, it is possible to write the
following:
I 1 > I2 (2)
Then, inserting into the formula above, we get that Imax = 4I1 and Imin = 0. This formula will be tested experimentally — if the
microexplosions will occur on the aluminum substrate at the power level at which microexplosions of polystyrene micro-
particles on a quartz substrate were not observed, so it is possible to draw a conclusion about the strengthening of the two beams
through their interference.
3. Experiment
Consider the installation, which was used in the observation process of the full-scale experiment with microexplosion of
polystyrene microparticles on a substrate coated with aluminium in thickness of 100 nm. The application of the aluminium
substrate was made with the use of plant «Carolina D 12 A» designed for magnetron sputtering on ceramic, silicon and other
substrates with sizes up to 100 mm. The following keys were added to the optical diagram in figure 1: 1 – continuous UV laser
DTL – 375 with wavelength 355 nm and maximal average power equals to 40 mV [4]; 2,3 – rotary mirrors; 4 – semitransparent
cubic; 5 – focused microobjective (20x); 6 – substrate covered by aluminum with polysterene microparticles; 7 – CCD – camera
FastVideo 500 E with resolution 640x480.
Now let’s move to the description of the experiment. The light by means of rotary mirrors and microscope objective is
focused into the required area of the substrate with microparticles. In view of the high reflection coefficient of aluminium (about
93-94%) the process of microexplosions on the aluminium substrate needed to be monitored in the reflected light. For separation
of the incident and the reflected beams it is used a cube with translucent mirrors. Reflected light falls on the camera and the
resulting image is processed on the computer.
Fig.1. Optical setup for microexplosions polysterene microparticles on substrate covered by aluminum.
Let’s turn to the experimental results. The original experiment took place at the maximum value of laser radiation power
obtained with the pulse frequency of 3000 Hz. But with this value there was a destruction of the substrate surface covered with
aluminum. Consequently, the beam power was reduced to a value of 6.17 kW, which stops the observed damage to the surface
of the substrate. Thus, it minimized the influence of melting and destruction of the substrate surface on the movement of
microparticles of polystyrene.
An experiment was carried out with deposition of polystyrene microparticles floating in the water on the substrate covered
with aluminum. As the result, it was obtained a footage of polystyrene microparticles movement after the explosion, which is
achieved by superposition of the incident and reflected beams of laser radiation. Now we will explain how we made these
conclusions.
Firstly, in order to eliminate the influence of melting and destruction of the substrate surface covered with aluminium on the
movement of polystyrene particles, the particles were inputted to the surface in the water. Thus, the water absorbs the portion of
energy that came from breaking the surface of the substrate.
Given that the light almost does not pass through the surface covered with aluminum, then all the power goes into heating the
surface (this effect was eliminated due to the choice of required capacity and the introduction of particles in solution with water),
and the remaining part is reflected (about 93%). We find that in the explosion of polystyrene microparticles affects only the
energy of the incident beam and the energy of the reflected beam.
In order to see whether the incident and reflected beams interact with each other or the main contribution is made only by the
incident beam, another experiment was carried out which eliminates these issues. The substrate covered with aluminium was
replaced by a quartz substrate with the transmittance of about 99%. Thus, if the former power of the laser radiation the
microexplosion of polystyrene microparticles will not occur it turns out that this reflected beam interacts with the incident beam
in a certain way.
3rd International conference “Information Technology and Nanotechnology 2017” 49
Computer Optics and Nanophotonics / V.S. Vasilev, R.V. Skidanov
After conducting full-scale experiments on a substrate covered with aluminum, there was an explosion of polystyrene
microparticles, in which a displacement of nearby microparticles of polystyrene occurred. In case of changing of substrate coated
with aluminium on a quartz substrate and leaving unchanged all the parameters of the scheme the explosion of polystyrene
particles was not observed. As the result, we can conclude that explosion of polystyrene microparticles occurs on a substrate
covered with aluminum due to the interaction of the incident and reflected beams.
It was also calculated the average rate of expansion of the polystyrene particles located on a substrate coated with aluminium
after the explosion of a nearby polystyrene particles. This value is 0.77 mm/s.
Fig.2. Results of the experiment on explosions polysterene microparticles using substrate covered by aluminum. Time interval between frames is equal to 10
ms.
Fig.3. Results of the experiment on explosions polysterene microparticles using quartz substrate. Time interval between frames is equal to 10 ms.
4. Conclusion
In the process of performing this work the following results were obtained:
1) An experiment was conducted, in which we discovered the existence of the interference between incident and reflected
waves using aluminum substrate.
2) The expansion velocity of the particles using a 20x focusing microobjective was experimentally calculated. The speed
value is 0.77 mm/s;
3) The parameters of explosion occurrence were found. The parameter is the average radiation power. The explosion
occurs when values are higher than 6.17 kW.
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Computer Optics and Nanophotonics / V.S. Vasilev, R.V. Skidanov
Acknowledgements
The work was partially funded by the RF Ministry of Science and Education as part of state-assigned task No.
3.3025.2017/PCh and by the Russian Foundation for Basic Research (RFBR) (grants Nos. 16-29-11744 ofi_m and 16-29-09528
ofi_m).
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