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DOI: https://doi.org/10.22184/1993-8578.2023.16.5.266.270
A two-stage nanopositioning system has been developed along three coordinates X, Y and Z with an accuracy of 0.1 nm. The nanopositioning system is intended for use in scanning probe microscopy, ultra-high resolution optical microscopy, and microlens microscopy. This paper considers an example of constructing a scanning capillary microscope based on the developed system of precision movements.
A two-stage nanopositioning system has been developed along three coordinates X, Y and Z with an accuracy of 0.1 nm. The nanopositioning system is intended for use in scanning probe microscopy, ultra-high resolution optical microscopy, and microlens microscopy. This paper considers an example of constructing a scanning capillary microscope based on the developed system of precision movements.
Теги: nanocapillary nanodisplacements probe microscopy scanning capillary microscopy зондовая микроскопия нанокапилляр наноперемещения сканирующая капиллярная микроскопия
INTRODUCTION
A compact miniaturised nanodisplacement system is in demand in many applications of physical experiment. The proposed solution can be successfully applied in scanning capillary (ion-conducting capillary [1, 2]) microscopy. In this case, the studied sample is placed at the bottom of a Petrie dish, being immersed in a salt solution. The probe is a nanocapillary with a cone-shaped end and an outlet opening of about 30–50 nm. In a scanning capillary microscope, the ionic current between two silver chloride electrodes is recorded. One of them is located in a nanocapillary filled with electrolyte and the second one is located in a salt solution in a Petrie dish. As the capillary approaches the sample surface, ionic current decreases. The decrease of ionic current in the nanocapillary corresponds to the nanocapillary location above the sample surface at a distance equal to the nanocapillary outlet diameter, i.e. at a distance of 30–50 nm.
The ionic current magnitude through the nanocapillary depends on the following factors:
nanocapillary geometry determined mainly by the outlet diameter rо;
applied electrical voltage U between the electrodes. This voltage is often set equal to 200 mV;
resistivity ρ of the electrolyte used (salt solution).
Let us consider the simplest geometry of a nanocapillary in the form of an upper cylindrical part of length L with inner radius r and a conical part Lo and an outlet of radius rо (Fig.1).
The total resistance R of the inner part of the capillary filled with electrolyte will be equal to:
R = ρL/(πr2) + ρLo/(πrro). (1)
The following values are valid for a good capillary:
r = 0,25 mm; L= 40 mm
ro = 25 nm; Lo = 10 mm.
Due to significant difference between r and ro (r/ro = 10000), the first summand in the resistance value R can be neglected. Hence, we obtain an approximate formula:
R = ρLo/(πrro). (2)
This formula can be converted using the angle between the vertical and the nanocapillary cone formation α, since the ratio r/Lo is almost equal to the tangent of angle α (tgα):
R = ρ/(πrotgα). (3)
Let us consider the case of capillary filling with physiological solution. Physiological solution is an aqueous solution of sodium chloride (NaCl) with mass fraction ω(NaCl) ≈ 0.9 %. The specific resistance of physiological solution is ρ = 120 Ohm∙cm at normal temperature (20 оС). For a capillary with the conical part length of 10 mm, an initial radius of 0.25 mm and the radius of the outlet equal to 25 nm, resistance is R = 300 MOhm.
Thus, the ionic current magnitude at voltage of 200 mV between the electrodes is:
I = U/R = 0,67 nА. (4)
MATERIALS AND METHODS
To prepare a nanocapillary, a glass blank is used with the 100 mm long tube with an outer diameter of 1 mm and an inner diameter of 0.5 mm. Two equivalent nanocapillaries are obtained from one blank. The nanocapillary is fabricated on a Sutter P-1000 or P-2000 puller. Adair Oesterle’s company excellently written guide to pulling nanocapillaries, Pipette Cookbook 2018 P-97 & P-1000 Micropipette Pullers, Ref F, Sutter Instrument Company (108 pages), is publicly available.
In a scanning capillary microscope, a nanocapillary moves vertically up and down in the range of tens of microns. This movement allows observing the living cells, including neuronal networks, whose height difference can be tens of microns. The sample is placed in a Petri dish in the holder of the nanopositioning system.
The nanopositioning system consist of two stages (Fig.2). The first of them is made using linear guides and stepper motors. The movement range in the X and Y axes is 12 mm. The minimum step varies from 0.16 µm to 2.5 µm.
The first mechanical stage has a three-axis piezo-ceramic platform with the following characteristics:
movement range in X and Y axes: 50 × 50 µm;
resolution in X and Y axes: 0.05 nm;
X-axis resonant frequency: 3000 Hz;
resonant frequency in the Y axis: 2000 Hz.
To move the nanocapillary, a linear piezo manipulator with a movement range of 30 μm and accuracy of 0.03 nm, or a Z stage as part of a three-axis XYZ piezo manipulator can be used. For optical control of the sample and nanocapillary position, an optical microscope with automated focusing is implemented in the nanopositioning system.
CONCLUSIONS
The developed system is an effective tool to study the biological objects by probe, optical and microlens microscopy methods without using labels, which is extremely relevant for biology and biomedicine [3, 4].
ACKNOWLEDGMENTS
The study of I.V.Yaminsky on detecting of nanopositioning system technical parameters was carried out with the financial support of the Physical Department of the Lomonosov Moscow State University (Registration subject 122091200048-7). The authors would like to thank T.O.Sovetnikov, Master’s degree student of Physical Department for drawing figures and A.N. Prokhorov, Master of Precision and Special Instruments, Chemistry Faculty, for making the working mock-up of the 1st stage of the nanopositioning system.
PEER REVIEW INFO
Editorial board thanks the anonymous reviewer(s) for their contribution to the peer review of this work. It is also grateful for their consent to publish papers on the journal’s website and SEL eLibrary eLIBRARY.RU.
Declaration of Competing Interest. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
A compact miniaturised nanodisplacement system is in demand in many applications of physical experiment. The proposed solution can be successfully applied in scanning capillary (ion-conducting capillary [1, 2]) microscopy. In this case, the studied sample is placed at the bottom of a Petrie dish, being immersed in a salt solution. The probe is a nanocapillary with a cone-shaped end and an outlet opening of about 30–50 nm. In a scanning capillary microscope, the ionic current between two silver chloride electrodes is recorded. One of them is located in a nanocapillary filled with electrolyte and the second one is located in a salt solution in a Petrie dish. As the capillary approaches the sample surface, ionic current decreases. The decrease of ionic current in the nanocapillary corresponds to the nanocapillary location above the sample surface at a distance equal to the nanocapillary outlet diameter, i.e. at a distance of 30–50 nm.
The ionic current magnitude through the nanocapillary depends on the following factors:
nanocapillary geometry determined mainly by the outlet diameter rо;
applied electrical voltage U between the electrodes. This voltage is often set equal to 200 mV;
resistivity ρ of the electrolyte used (salt solution).
Let us consider the simplest geometry of a nanocapillary in the form of an upper cylindrical part of length L with inner radius r and a conical part Lo and an outlet of radius rо (Fig.1).
The total resistance R of the inner part of the capillary filled with electrolyte will be equal to:
R = ρL/(πr2) + ρLo/(πrro). (1)
The following values are valid for a good capillary:
r = 0,25 mm; L= 40 mm
ro = 25 nm; Lo = 10 mm.
Due to significant difference between r and ro (r/ro = 10000), the first summand in the resistance value R can be neglected. Hence, we obtain an approximate formula:
R = ρLo/(πrro). (2)
This formula can be converted using the angle between the vertical and the nanocapillary cone formation α, since the ratio r/Lo is almost equal to the tangent of angle α (tgα):
R = ρ/(πrotgα). (3)
Let us consider the case of capillary filling with physiological solution. Physiological solution is an aqueous solution of sodium chloride (NaCl) with mass fraction ω(NaCl) ≈ 0.9 %. The specific resistance of physiological solution is ρ = 120 Ohm∙cm at normal temperature (20 оС). For a capillary with the conical part length of 10 mm, an initial radius of 0.25 mm and the radius of the outlet equal to 25 nm, resistance is R = 300 MOhm.
Thus, the ionic current magnitude at voltage of 200 mV between the electrodes is:
I = U/R = 0,67 nА. (4)
MATERIALS AND METHODS
To prepare a nanocapillary, a glass blank is used with the 100 mm long tube with an outer diameter of 1 mm and an inner diameter of 0.5 mm. Two equivalent nanocapillaries are obtained from one blank. The nanocapillary is fabricated on a Sutter P-1000 or P-2000 puller. Adair Oesterle’s company excellently written guide to pulling nanocapillaries, Pipette Cookbook 2018 P-97 & P-1000 Micropipette Pullers, Ref F, Sutter Instrument Company (108 pages), is publicly available.
In a scanning capillary microscope, a nanocapillary moves vertically up and down in the range of tens of microns. This movement allows observing the living cells, including neuronal networks, whose height difference can be tens of microns. The sample is placed in a Petri dish in the holder of the nanopositioning system.
The nanopositioning system consist of two stages (Fig.2). The first of them is made using linear guides and stepper motors. The movement range in the X and Y axes is 12 mm. The minimum step varies from 0.16 µm to 2.5 µm.
The first mechanical stage has a three-axis piezo-ceramic platform with the following characteristics:
movement range in X and Y axes: 50 × 50 µm;
resolution in X and Y axes: 0.05 nm;
X-axis resonant frequency: 3000 Hz;
resonant frequency in the Y axis: 2000 Hz.
To move the nanocapillary, a linear piezo manipulator with a movement range of 30 μm and accuracy of 0.03 nm, or a Z stage as part of a three-axis XYZ piezo manipulator can be used. For optical control of the sample and nanocapillary position, an optical microscope with automated focusing is implemented in the nanopositioning system.
CONCLUSIONS
The developed system is an effective tool to study the biological objects by probe, optical and microlens microscopy methods without using labels, which is extremely relevant for biology and biomedicine [3, 4].
ACKNOWLEDGMENTS
The study of I.V.Yaminsky on detecting of nanopositioning system technical parameters was carried out with the financial support of the Physical Department of the Lomonosov Moscow State University (Registration subject 122091200048-7). The authors would like to thank T.O.Sovetnikov, Master’s degree student of Physical Department for drawing figures and A.N. Prokhorov, Master of Precision and Special Instruments, Chemistry Faculty, for making the working mock-up of the 1st stage of the nanopositioning system.
PEER REVIEW INFO
Editorial board thanks the anonymous reviewer(s) for their contribution to the peer review of this work. It is also grateful for their consent to publish papers on the journal’s website and SEL eLibrary eLIBRARY.RU.
Declaration of Competing Interest. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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