Controlled focusing of silver nanoparticles beam to

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nanoparticles on the substrate focused by using a number of aero-. 61 dynamic lens [8] or coaxial nozzles [9]. In this approach, the source. 62 of nanoparticles is ...
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Microarticle

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Controlled focusing of silver nanoparticles beam to form the microstructures on substrates

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A.A. Efimov a,⇑, G.N. Potapov b, A.V. Nisan b, V.V. Ivanov a

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a b

Moscow Institute of Physics and Technology, Dolgoprudny, Russia Ostec Enterprise Ltd., Moscow, Russia

a r t i c l e

i n f o

Article history: Received 20 November 2016 Received in revised form 30 December 2016 Accepted 31 December 2016 Available online xxxx

a b s t r a c t The aerodynamic focusing in the coaxial nozzle and deposition on substrates of silver nanoparticles beams at the high subsonic speeds has been studied. The multi-spark discharge generator was used as a source of silver nanoparticles. We established that controlling the high-speed sheath flow allows to provide the minimization of the aerosol beam diameter for 4 times and printing of silver lines with width up to 60 lm using a nozzle 100 lm in outlet diameter. It was realized due to usage of high-speed beams of silver nanoparticle agglomerates, with the size of 25–110 nm, consisting of the primary particles with diameter of 5–10 nm. The agglomeration effect of aerosol nanoparticles plays a positive role providing particle deposition onto a substrate and substantially reducing diffusion broadening of an aerosol beam. Ó 2017 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).

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nanoparticles, as well as utilization of the solvent in the printing process. The second approach is based on the dry deposition of aerosol nanoparticles on the substrate focused by using a number of aerodynamic lens [8] or coaxial nozzles [9]. In this approach, the source of nanoparticles is ink as well, and the method of getting the aerosol nanoparticle beams for printing turns out to be a complicated one and has quite a low productivity. It includes the processes of obtaining the microdroplets by spraying, drying, charging and electrical mobility separation for the allotment of nanoparticles fraction and then aerodynamic particles focusing. For the high-yield realization of aerosol jet printing by nanoparticles, the most perspective method would be different, as there would be no ink with solvents for aerosol generation, and a simpler and effective system of aerodynamic focusing would be applied. In the present work, we suggest a new approach based on the usage for the source of solid nanoparticles the process of electrical erosion of electrodes in the pulsed gas discharge [10,11], and for the focusing system a coaxial flow nozzle operating at the high subsonic speed. Relying on the physical effect of agglomeration of aerosol nanoparticles at high-concentration in flow, the focusing and deposition of silver nanoparticle agglomerates is realized, with the size of 25–110 nm, consisting of the primary particles with diameter of 5–10 nm which have a higher sintering activity.

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Experimental

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For obtaining the aerosol nanoparticles we used the multi-spark discharge generator, where in the processes of electrical erosion of

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Introduction

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Along with the wish for miniaturization of the elements of microstructures, an important aim in printed electronics is the realization of printing processes using nanoparticles [1,2]. Due to the high activity of nanoparticles of about 10 nm in size, the formed microstructures may be sintered, compared with the microparticles at considerably lowered temperatures [3], which allows us to maintain printing on more cheap and flexible plastic substrates [4]. Therefore, the development of new printing methods, which would allow us to get the nanoparticles up to the surface of the substrate with the micron precision of positioning, is mostly in demand. The most perspective direction is the deposition of focused beams of aerosol nanoparticles on a substrate [1,5]. The research on focusing and deposition of aerosol nanoparticles faced serious difficulties related to such fundamental properties of nanoparticles as high diffusivity and low inertia [6]. To overcome those main limitations for printing by aerosol nanoparticle beams, two approaches were implemented. The first approach used the aerosol deposition of liquid microdroplets with nanoparticles inside them [7]. The focusing process of liquid microdroplets is maintained in the simple system of coaxial nozzles or constricted Microcapillaries, where the mechanisms of focusing and deposition act as for microparticles [1]. This approach is close to the ink jet printing with microdroplets and has its drawbacks related to the necessity of preparation and keeping inks with

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⇑ Corresponding author. E-mail address: [email protected] (A.A. Efimov).

http://dx.doi.org/10.1016/j.rinp.2016.12.052 2211-3797/Ó 2017 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Please cite this article in press as: Efimov AA et al. Controlled focusing of silver nanoparticles beam to form the microstructures on substrates. Results Phys (2017), http://dx.doi.org/10.1016/j.rinp.2016.12.052

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silver electrodes in the atmosphere of pure air silver nanoparticles are synthesized with the primary diameter about 5–10 nm. Detailed information about the used spark discharge generator can be found in studies [10] and [11]. It is found from [12] that the median diameter and total number concentration of nanoparticles produced by spark discharge generator remained constant to within about ±15 and ±20%, respectively. In the gas flow nanoparticles united into agglomerates, the size of which depends on the particle concentration and the residence time of aerosol. Uniformity generation of aerosol nanoparticles was controlled by measuring the particle size distribution by the aerosol spectrometer SMPS 3936 (TSI Inc.). From the generator the aerosol nanoparticles moved for focusing into the coaxial aerodynamic nozzle with the outlet diameter Dn = 100 lm (Fig. 1a). In the experiments we used a commercial nozzle type from Optomec Inc. without additional optimizations of the geometry. Then the focused aerosol beam was directed to the glass substrate for deposition. The distance between the nozzle and substrate S, as well as the speed of motion of the substrate u were fixed in the experiment as 0.5 mm and 10 mm/s, respectively. This mode of deposition was optimized to obtain narrow lines and the applicability of a simplified model of inertial particle deposition from the nozzle to substrate according to a theory from [13]. The aerosol flow Qa entered the coaxial nozzle through the inner cylindrical channel, while the sheath flow of nitrogen gas Qsh was inserted through the outer conically converging axisymmetrical channel. Thus the particle movement from the central line of the flow was prevented, and the hydrodynamic focusing of the aerosol beam was provided. The inner channel of the nozzle is characterized by its smooth inner wall and gradual reduction of the channel diameter from inlet to outlet from 0.7 mm to 100 lm at the length L = 30 mm. The jet-exit diameter of aerosol beam Db was calculated from the aspect ratio of the aerosol flow rate Qa and sheath flow rate Qsh, neglecting the diffusion broadening taken from [9]:

sffiffiffiffiffiffiffi Qa ; Db ¼ Dn QR

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where QR = (Qa + Qsh)  total flow rate. In the experiments on focusing at the fixed value of the aerosol flow rate Qa the sheath flow rate Qsh was regulated in the range from 36 to 110 cm3/min. Aerosol nanoparticles before their entering the nozzle were characterized by the aerosol spectrometer and transmission electron microscope (TEM), JEM-2100 (JEOL), selecting the fraction of aerosol and nanoparticles on the mesh grid from the flow Fig. 1b demonstrates the particle size distribution at the

stage of entering the nozzle from electrical mobility measurements in the aerosol and TEM-image of such nanoparticles (in the insertion). Fig. 1b shows the mass particle size distribution which was obtained by transforming number particle size distribution. It has been found that while entering the nozzle the size of agglomerates is in the range from 25 to 110 nm, and their average mass size is about 60 nm. TEM-image proves the ability of nanoparticles for agglomeration and states the typical sizes of agglomerates. It is worth mentioning that the electrical mobility measurements provide the equivalent diffusion size of agglomerates, typical in the estimation of the diffusion broadening of the aerosol beam in the sheath gas. In the process of moving the substrate relatively to the focused aerosol beam, we formed the line of deposited silver nanoparticles on the substrate. The substrate is moved in one direction automatically by using the XY coordinate table. The lines had a length of about 15 mm. The width of formed lines was measured by using the optical microscope, and the microstructure of nanoparticles in lines was studied by the scanning electron microscope (SEM), JSM-7001F (JEOL). Additionally, the nanoparticles in lines were also characterized by TEM. The samples for TEM were prepared on the copper grid with carbon amorphous film by the contact transition from the surface of the formed line.

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Results and discussion

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In the series of experiments by varying the sheath flow rate Qsh, we controlled the diameter of the aerosol beam and formed the lines of nanoparticles with the controlled width W on the substrate. The total flow rate QR, was increased only at the expense of the increasing the sheath flow rate Qsh at the aerosol flow rate Qa to be constant. The given dependences of the line width W and the diameter of aerosol beam Db, calculated by the Eq. (1) from the total flow rate QR and the flow velocity at the outlet from the nozzle V are given in Fig. 2. The insertion in Fig. 2 shows a typical image of the line obtained in the optical microscope. In Fig. 2 we can see that the increasing of the total flow QR from 78 to 152 cm3/min leads to the decreasing diameter of aerosol beam Db by more than 4 times from 100 to 23 lm, respectively. Given that the width of the line W printed on the substrate also decreases by nearly 2.5 times, from 160 to 60 lm. This result demonstrates the realization of the aerodynamic focusing of the nanoparticles beam in the coaxial nozzle. It should be noted that the width of the printed line W is much more than the diameter of the aerosol beam Db, which is logically explained by the lateral spreading of the gas flow at the interaction with the substrate. The

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Fig. 1. Schematic diagram of the focusing and deposition of aerosol nanoparticles (a); Particle size distribution of aerosol nanoparticles measured before their entering the nozzle by the aerosol spectrometer and corresponding TEM-images on the inset (b).

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16]. In the performed experiments the main mechanism of deposition of nanoparticles on the substrate was inertial deposition. Inertial deposition of nanoparticles can be realized at high velocity gas flow, large particle size and high density particle. With the aim of evaluating an effective depositing of nanoparticles on the substrate in the given geometry of focusing the aerosol beam at varying the flow velocity in the nozzle the cutoff diameter of the particles dp50 was calculated by the Eq. (2) taken from [13]:

pffiffiffiffiffi dp50 C c ¼

sffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 9gDn ðStk50 Þ ; qp V

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ratio of these sizes W/Db is increasing from 1.6 to 2.8 at the increasing velocity of flow at the outlet of the nozzle V from 165 to 322 mm/s, respectively. This increase can be accounted for by a diffusion broadening of the aerosol beam, which has a greater influence at its less diameter. The analysis of the microstructure of formed lines in SEM has shown that the typical sized of the deposited agglomerates of nanoparticles are in the range of 50–100 nm (Fig 3a). About the same sizes of agglomerates were observed taking measurements at the inlet of the nozzle by the aerosol spectrometer, which testifies to the insignificant additional agglomeration of nanoparticles at the aerosol flow motion in the nozzle (Fig. 1b). The investigation of the fine structure of agglomerates by TEM (Fig. 3b) has proved that the deposited nanoparticles are agglomerates which consist of the primary nanoparticles with the diameter of 5–10 nm. This evidence proves the maintaining of the high-activity nanoparticles in the process of aerosol depositing on the substrate, which should help the sintering of the formed lines at lowered temperatures. Fig. 3c shows a typical SEM image of the cross-sectional profile of a sintered line. The cross-section profile of the line has a bellshaped form with maximum thickness and width equal to 15 ± 2 and 89 ± 4 lm, respectively. The line width 89 ± 4 lm measured by analyzing SEM images coincides with the data of optical microscopy 86 ± 4 lm within the range of uncertainty, see Fig. 2 (insert) and Fig. 3c. It is known that inertial deposition of nanoparticles is possibly used for the collection and measurement of nanoparticles [14–

Fig. 3. SEM-image (a) of agglomerates of silver nanoparticles deposited on the glass substrate (b) corresponding TEM-image (c) and the cross-sectional profile of the line.

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ð2Þ

h  i 0:39dp50 k – slip factor; k – where C c ¼ 1 þ dp50 2:34 þ 1:05 exp k

Fig. 2. The dependences of the beam diameter Db and width of the line W from the total flow rate QR and gas velocity at the exit of the nozzle V. The image of the printed line in the optical microscope is on the inset.

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mean free path of the gas; g – viscosity of the gas; Stk50 – Stokes number is 0.24 for 50% collection efficiency; qp – particle density; V – flow velocity. Eq. (2) is a simplified model for calculating the cut-off diameter of the nanoparticles dp50 that come from the nozzle and deposited on the substrate. According to a study [13] the Eq. (2) is valid at Reynolds numbers Re from 500 to 3000 and a ratio of S/Dn from 1 to 5. In the presented experiments Re and S/Dn is equal to 1000–2100 and 5, respectively. For the experiment conditions, the monotonously decreasing dependence of the cutoff diameter from the flow velocity V at the outlet from the nozzle is obtained (Fig. 4a), which demonstrates the decreasing the cutoff diameter dp50 from 10 to 5 nm at the increasing of the flow velocity at the range from 165 to 322 m/s. The possibility of inertial deposition of nanoparticles on a substrate is achieved by using high-velocity gas flow up to 322 m/s and Ag particles with a high density 10.5 g/cm3. It should be noted that the real cutoff particle size can be more than calculated cutoff diameter dp50 due to the effective density of the aggregates and the difference between velocities of gas and nanoparticles [15,17]. Because the deposited nanoparticles are the agglomerates with the sizes more than 25 nm, the main part

Fig. 4. The dependences of the cutoff diameter dp50 (a), and the root mean squared diffusion displacement xrms for particles of the following sizes: 5, 25, 60 and 110 nm (b) from the gas velocity V at the exit of the nozzle.

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of focused nanoparticles should reach the surface of the substrate and deposit on it. On the surface of the substrate a certain broadening of the aerosol beam as a result of the lateral spreading of gas flow on its surface should be observed. The diameter of the focused beam is affected by Brownian motion of nanoparticles leading to the broadening of the beam by the value of the typical root mean squared diffusion displacement xrms, defined by the equation [13]:

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pffiffiffiffiffiffiffiffi 2Dt;

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xrms ¼

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D – particle diffusion coefficient; t – particle residence time. For the ranges of flow velocity, realized in the experiments, the diffusion displacements xrms of particles with sizes 5, 25, 60 b 110 nm were calculated. The findings were demonstrated in Fig. 4b in depend of the flow velocity at the nozzle outlet. If there were any primary nanoparticles of the diameter 5 nm, the diffusion broadening of the aerosol beam would be quite high and comprise from 31 to 44 lm by the radius of the flow. At such a significant displacement of nanoparticles for the residence time of flow along the nozzle they should reach an inner wall and deposit on it. Fig. 4b shows that for agglomerates of the size ranges 25–110 nm, which comprise the main part of the aerosol used in printing, the diffusion displacement is from 2 to 9 lm, which has low influence on the broadening of the aerosol beam in comparison to the calculated value (1). At the higher velocity, when the minimal value of aerosol beam diameter is reached, the diffusion displacement is less than 7 lm.

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Conclusion

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The combination of experimental data and theoretical evaluations testify to the realization of possibility of aerodynamic focusing of silver aerosol nanoparticles for forming the microstructures on substrates and the potential for the further decreasing of the diameter of focused beam and patterned lines with the use of high-speed flows of agglomerated nanoparticles.

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Acknowledgements

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This work was supported by the Russian Science Foundation (project # 15-19-00190).

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References

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[1] Hoey JM, Lutfurakhmanov A, Schulz DL, Akhatov IS. A review on aerosol-based direct-write and its applications for microelectronics. J Nanotechnol 2012;2012:e324380. http://dx.doi.org/10.1155/2012/324380. [2] Kim N-S, Han KN. Future direction of direct writing. J Appl Phys 2010;108:102801. http://dx.doi.org/10.1063/1.3510359. [3] Peng P, Hu A, Gerlich AP, Zou G, Liu L, Zhou YN. Joining of silver nanomaterials at low temperatures: processes, properties, and applications. ACS Appl Mater Interfaces 2015;7:12597–618. http://dx.doi.org/10.1021/acsami.5b02134. [4] Vaillancourt J, Zhang H, Vasinajindakaw P, Xia H, Lu X, Han X, et al. All ink-jetprinted carbon nanotube thin-film transistor on a polyimide substrate with an ultrahigh operating frequency of over 5 GHz. Appl Phys Lett 2008;93:243301. http://dx.doi.org/10.1063/1.3043682. [5] Seifert T, Sowade E, Roscher F, Wiemer M, Gessner T, Baumann RR. Additive manufacturing technologies compared: morphology of deposits of silver ink using inkjet and aerosol jet printing. Ind Eng Chem Res 2015;54:769–79. http://dx.doi.org/10.1021/ie503636c. [6] Wang X, Kruis FE, McMurry PH. Aerodynamic focusing of nanoparticles: I. guidelines for designing aerodynamic lenses for nanoparticles. Aerosol Sci Technol 2005;39:611–23. http://dx.doi.org/10.1080/02786820500181901. [7] Mahajan A, Frisbie CD, Francis LF. Optimization of aerosol jet printing for highresolution, high-aspect ratio silver lines. ACS Appl Mater Interfaces 2013;5:4856–64. http://dx.doi.org/10.1021/am400606y. [8] Wang X, McMurry PH. An experimental study of nanoparticle focusing with aerodynamic lenses. Int J Mass Spectrom 2006;258:30–6. http://dx.doi.org/ 10.1016/j.ijms.2006.06.008. [9] Park J, Jeong J, Kim C, Hwang J. Deposition of charged aerosol particles on a substrate by collimating through an electric field assisted coaxial flow nozzle. Aerosol Sci Technol 2013;47:512–9. http://dx.doi.org/10.1080/ 02786826.2013.767981. [10] Efimov AA, Ivanov VV, Bagazeev AV, Beketov IV, Volkov IA, Shcherbinin SV. Generation of aerosol nanoparticles by the multi-spark discharge generator. Tech Phys Lett 2013;39:1053–6. http://dx.doi.org/10.1134/ S1063785013120067. [11] Efimov A, Lizunova A, Sukharev V, Ivanov V. Synthesis and characterization of TiO2, Cu2O and Al2O3 aerosol nanoparticles produced by the multi-spark discharge generator. Korean J Mater Res 2016;26:123–9. http://dx.doi.org/ 10.3740/MRSK.2016.26.3.123. [12] Kreyling WG, Biswas P, Messing ME, Gibson N, Geiser M, Wenk A, et al. Generation and characterization of stable, highly concentrated titanium dioxide nanoparticle aerosols for rodent inhalation studies. J Nanoparticle Res 2011;13:511–24. http://dx.doi.org/10.1007/s11051-010-0081-5. [13] Hinds WC. Aerosol technology: properties, behavior, and measurement of airborne particles. 2 edition. New York: Wiley-Interscience; 1999. [14] Yli-Ojanperä J. Improving the nanoparticle resolution of the ELPI. Aerosol Air Qual Res 2010. http://dx.doi.org/10.4209/aaqr.2009.10.0060. [15] Barone TL, Lall AA, Zhu Y, Yu R-C, Friedlander SK. Inertial deposition of nanoparticle chain aggregates: theory and comparison with impactor data for ultrafine atmospheric aerosols. J Nanoparticle Res 2006;8:669–80. http://dx. doi.org/10.1007/s11051-006-9128-z. [16] Tsai C-J, Liu C-N, Hung S-M, Chen S-C, Uang S-N, Cheng Y-S, et al. Novel active personal nanoparticle sampler for the exposure assessment of nanoparticles in workplaces. Environ Sci Technol 2012;46:4546–52. http://dx.doi.org/10.1021/ es204580f. [17] Huang C, Nichols WT, O’Brien DT, Becker MF, Kovar D, Keto JW. Supersonic jet deposition of silver nanoparticle aerosols: correlations of impact conditions and film morphologies. J Appl Phys 2007;101:64902. http://dx.doi.org/ 10.1063/1.2710304.

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Please cite this article in press as: Efimov AA et al. Controlled focusing of silver nanoparticles beam to form the microstructures on substrates. Results Phys (2017), http://dx.doi.org/10.1016/j.rinp.2016.12.052