=Paper=
{{Paper
|id=Vol-1638/Paper4
|storemode=property
|title=The microturbine rotation by not circular light beam formed by vortex axicon
|pdfUrl=https://ceur-ws.org/Vol-1638/Paper4.pdf
|volume=Vol-1638
|authors=Sofia V. Ganchevskaya,Roman V. Skidanov
}}
==The microturbine rotation by not circular light beam formed by vortex axicon ==
https://ceur-ws.org/Vol-1638/Paper4.pdf
Computer Optics and Nanophotonics
THE MICROTURBINE ROTATION BY NOT
CIRCULAR LIGHT BEAM FORMED BY VORTEX
AXICON
S.V. Ganchevskaya, R.V. Skidanov
Image Processing Systems Institute - Branch of the Federal Scientific Research Centre “Crys-
tallography and Photonics” of Russian Academy of Sciences, Samara, Russia
Samara National Research University, Samara, Russia
Abstract. The using possibility of the vortex light beam with topological
charges 2 and 5 for the rotation of the micromechanical element (microturbine)
was considered. The results of the full-scale experiment on the optical rotation
of the special form microturbine were presented. We evaluated the force mo-
ment, acting the microturbine.
Keywords: microturbine, optical rotation, light beam.
Citation: Ganchevskaya SV, Skidanov RV. The microturbine rotation by not
circular light beam formed by vortex axicon. CEUR Workshop Proceedings,
2016; 1638: 24-31. DOI: 10.18287/1613-0073-2016-1638-24-31
Introduction
The light beam with the orbital angular moment can be formed by the diffractive opti-
cal elements for a defined shape micromechanical component to optimize the process
of the light energy transformation into mechanical energy. Such beams are widely
used to rotate microscopic objects with the size of 0.1-10 microns, which is confirmed
by the numerous publications. For example, the [1] work shows the optically con-
trolled micromechanical system with the Archimedes helix as a mechanical drive in
the form of the central sphere with three blades which were produced by two-photon
polymerization. The laser beam is focused on the micro systems, the microhelical
falls into a trapping site at the point of beam application and rotates simultaneously.
In this article we research the dependence of the micro-rotor rotation speed with
blades and without them, respectively equal to 1.9 min-1/mW and 13.5 min-1/mW.
The dependence of the rotation speed on thickness of the blade and central part of the
helix was considered in the research [2]. However, it should be noted that the primary
mechanism for the increase of the microscopic objects rotation speed is the power
increase of the light beam, but the three-dimensional structures based on polymers do
not have sufficient beam resistance. The metallized, cross-shaped rotors (diameter of
Information Technology and Nanotechnology (ITNT-2016) 24
Computer Optics and Nanophotonics Ganchevskaya SV, Skidanov RV…
40 μm) was developed for the microdrive motors by scanning of the laser low power
beam to solve this problem in the research [3]. The analysis of the light pressure ex-
erted on the blade was carried out, and its results show that the oblique blade can
generate more rotational moment than the horizontal blade due to the reflection of the
incoming Gaussian beam. The metallized microturbine (diameter of 60 μm, height 6
μm) which is effectively used to create the movement of the fluid stream was also
developed in the research [4]. Based on the two-photon polymerization efforts for
miniaturization of the diffractive optical element (DOE) were efforted to form the
light vortex beams [5]. As a result, the DOE for the formation of a vortex beam was
comparable in the scale with the rotated microscopic objects (diameter of 9 μm, at a
resolution of 0.3 μm).
However, the number of the researches on the use of light vortex beams with micro-
scopic objects in a rarefied medium (air or vacuum), is not enough, due to the signifi-
cant technical difficulties during the experiments realization. Therefore, it is im-
portant to develop a system where the light beams and micromechanical elements will
be designed to each other and are optimized for the operation in air or vacuum. But
with the use of the diffractive optical elements we are able to realize the system where
the operating micromechanical element will be illuminated by the light beam with the
orbital angular moment, which will be formed to fit the shape of the microscopic ob-
jects, so that the rotation moment transmission can occur due to the light pressure as a
result of the light reflection from the surface. As the result, it is possible to minimize
the light absorption by the microscopic object, and consequently its thermal effect.
One the way to minimize the thermal effect is the distribution of the light beam inten-
sity by the maximum area. Such vortex beams exist, for example, Bessel beams [6].
However, Bessel beams are not very suitable, because the intensity of rings sharply
decreases with the number increase. It is easy to use the superposition of the vortex
beams that due to the gradual increase of the topological charge will provide the
change of the vortex beam size to realize the estimated distribution of the intensity
[7]. These beams allow different types of the impact on the microscopic object. The
research [7] shows in details the different variations of the topological charge and the
estimated effect of these beams on the microscopic objects. Furthermore, despite the
vortex nature of beams, this effect does not necessarily lead to the rotation of the mi-
croscopic object as the research [8] shows the linear trap with anisotropic behavior on
the basis of these vortex superpositions. However, if the condition contained in the
research [9] is met, any beam obtained by the method described in the research [7],
can be used to rotate microscopic objects. In this case, the configuration of a required
intensity distribution can also be realized automatically [10]. In this research we con-
sider one of the superpositions, which is ideal to rotate the microscopic objects of the
special form, obtained by the method of the research [7, 10].
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Computer Optics and Nanophotonics Ganchevskaya SV, Skidanov RV…
1 Formation of the superposition of light fields by vortex
axicons for the microturbine rotation
To rotate the microturbine, it was decided to use one of the beams represented in the
research [7], which meets the requirements [9]. To select the light beam, we were
guided by the following considerations:
- the tilt of the wavefront at each point of the beam must be perpendicular to the
surface of the microturbine blade;
- the beam must satisfy the requirements of the intension distribution in the polar
angle[8].
The Figure 1 shows the phase function of the DOE (Fig. 1a), and formed intensity
distribution (Fig. 1b) and the beam phase (Fig. 1c).
a) b)
c)
Fig. 1. Phase function of the DOE (a), the intensity distribution in the far field of diffraction
(b), the phase of the beam (c)
Initially, this beam is assumed to rotate the microturbines from an opaque material,
however, this beam enables to rotate the set of the polystyrene micropatricles, and as
will be shown below, the beam successfully rotates the transparent microturbines.
To minimize thermal effect on the microturbine it is necessary to form the light beam
in the way that the intensity of the beam has been distributed over the maximum area
and the beam size was approximately comparable to the size of the microturbine (Fig.
2). Also, for efficient transmission of the rotation moment from the vortex beam to
the microturbine the following requirement should be satisfied: the intension, acting
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Computer Optics and Nanophotonics Ganchevskaya SV, Skidanov RV…
the microturbine blade, is on the same level, according to its position, it is achieved
on the basis of the intension distribution in the polar angle [9].
R
I S ( ) I (r, ) dr const (1)
0
where I (r, φ) is the intensity of the vortex beam in polar coordinates centered on the
beam axis, Is is the total intensity of the beam at the current narrow sector.
а) b)
c)
Fig. 2. The phase function of the DOE (a), the beam intensity distribution in the far field of the
diffraction (b), the phase of the beam in the far field of the diffraction (c).
The requirement is satisfied for the beam shown in the Figure 2b. The Figure 3 shows
the Is distribution according to the polar angle.
Fig. 3. The total intensity distribution of the generated beam
The deviation of the Is from the average value does not exceed 0.05.
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Computer Optics and Nanophotonics Ganchevskaya SV, Skidanov RV…
2 Experiments on the rotation of the microturbine
The microscopic objects of the special form (microturbines) were designed in order to
realize the rotation experiment. The circular laser work station (CLWS-2014) was
used for this purpose. The optical setup, which scheme shown in the Figure 2, was
used to form the complicated vortex beams and to focus them on the microturbines.
The laser with a wavelength of 532 nm and a maximum power of 4 W was used as the
radiation source. The laser beam input is realized from below to reduce the friction
which is increased when the laser beam is focused on the top and presses the particles
to the substrate by the light pressure. The beam was increased to a diameter of about
2.3 mm by the collimator, and then was limited to 2 mm by the iris aperture to match
the size of the beam to the size of the DOE. The microlens 16x were used to focus the
beam and to form the operation area image. The microturbines were placed in a cell
with water and salt was added to increase its density. Because the density of the resist
material whereof the microturbine was produced is 1200 kg/m3, that is much higher
than the water density, the salt addition reduces the microturbine weight and conse-
quently decreases friction.
Fig. 4. The optical scheme of the microturbines rotation setup installation. The optical scheme
uses the keys: 1 - the laser with a wavelength of 532 nm and a maximum power of 4 W; 2 -
collimator; 3, 5, 12 – rotating mirror; 4 - the aperture; 6 - axicon; 7 - a focusing microlens (×
16); 8 - substrate with microturbines; 9 – imaging microlens (× 16); 10 - spotlight; 11 – half-
transmitting rotating mirror; 13 - charge-coupled devices camera (CCD).
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Computer Optics and Nanophotonics Ganchevskaya SV, Skidanov RV…
The operation area was illuminated with white light from a standard illuminator. The
recoding was carried out by the CCD camera and the spectral filter was placed in
front of it. The Figure 3 shows the stages of the microturbine rotation.
a) b) c)
d)
Fig. 5. The stages of the polymer microturbine rotation with the interval of 2 s in the beam with
the topological charges 5, 2, 5
The Figure 5 shows that the rotation of the microturbine with the diameter of 100 μm
was realized by the focused light beam. We calculate the rotating speed of the micro-
turbine and the moment of the friction, acted it, using the first and the last image. We
find the coordinates of the blade in position before and after rotation. To calculate the
friction moment we use the formula for the moment of friction acting the wheel of the
terminating radius[11]:
M 1,94 R4 3 , (1)
where R is a radius of the microturbine, is the water density, - viscosity factor at
20°C, - the rotating speed.
The rotating speed of the microturbine was 0.056 c -1, and the moment of the rotating
intensity acting it is 2.87 fmN m . This enables the evaluation of the total intensity
exerted on the microturbine by the beam – it is about 100 pN.
The weight of the turbine is decreased with adding salt, which is resulted in micro-
turbine rotation. However, there are some difficulties: before each intake of the drop it
is necessary to heat the solution in the water bath for several minutes, but even in this
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Computer Optics and Nanophotonics Ganchevskaya SV, Skidanov RV…
case the salt is not completely dissolved - figures show salt crystals, which are the
obstacle for the microturbine rotation. Therefore, another method based on the high-
frequency vibration was used to minimize the friction. The special device for the crea-
tion of the high-frequency mechanical vibrations was added to the setup. The experi-
ment was realized using light traps, designed for the microturbine rotation (Fig. 2b).
a) b)
c) d)
Fig. 6. Stages of microturbine rotation, taken with an interval of 2 second
The microturbine rotation speed at high-frequency vibrations is that exceeds the speed
of microturbine rotation in salt brine using a beam, shown in the Figure 1 b. It proves
the effectiveness of the proposed method to the experiment realization.
Conclusion
The complex vortex beam with topological charges 2 and 5, in spite of the non-
circular structure that allows the microturbine, that matches in the form with its wave-
front, to be rotated. It is necessary to reduce the weight of the microturbines by in-
creasing the fluid density for the successful experiments with such large objects as the
microturbine (diameter 100 μm). The intensity moment acting the microturbine was
about 3 fmN, which is quite a high value within the parameters of the optical circuit
used in the experiment. We proved the perspective of the vibration use in the rotation
experiments.
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Acknowledgements
The work was funded RSF grant 14-19-00114.
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