OPENSUBJECT AREAS:
NANOWIRESSYNTHESIS AND PROCESSING

Received
25 June 2014
Accepted
17 July 2014
Published
4 August 2014

Correspondence andrequests for materials
should be addressed toT.Y. (yanagi32@
sanken.osaka-u.ac.jp)

Nanoscale Size-Selective Deposition of
Nanowires by Micrometer Scale
Hydrophilic Patterns
Yong He1, Kazuki Nagashima1, Masaki Kanai1, Gang Meng1, Fuwei Zhuge1, Sakon Rahong1, Xiaomin Li2,
Tomoji Kawai1 & Takeshi Yanagida1
1

The Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka Ibaraki, Osaka, 567-0047, Japan, 2Shanghai
Institute of Ceramics, Chinese Academy of Sciences, Shanghai, 200050, China.

Controlling the post-growth assembly of nanowires is an important challenge in the development offunctional bottom-up devices. Although various methods have been developed for the controlled assemblyof nanowires, it is still a challenging issue to align selectively heterogeneous nanowires at desired spatial
positions on the substrate. Here we report a size selective deposition and sequential alignment of nanowires
by utilizing micrometer scale hydrophilic/hydrophobic patterned substrate. Nanowires dispersed within oil
were preferentially deposited only at a water/oil interface onto the hydrophilic patterns. The diameter size ofdeposited nanowires was strongly limited by the width of hydrophilic patterns, exhibiting the nanoscale size
selectivity of nanowires deposited onto micrometer scale hydrophilic patterns. Such size selectivity was dueto the nanoscale height variation of a water layer formed onto the micrometer scale hydrophilic patterns. We
successfully demonstrated the sequential alignment of different sized nanowires on the same substrate by
applying this size selective phenomenon.

Designing the post-growth assembly of nanowires on the substrate offers a fascinating way to explore novel
functional nanoscale devices. In general, such assembling processes of nanowires can be performed atrelatively low temperatures1–26, which are much lower than typical nanowire growth temperatures27–32.
Therefore, this assembling method allows us to integrate single crystalline nanowires, which are grown at
relatively high temperatures, on various substrates via low temperature processes. This is a clear feature of theassembling method, since high temperature processes limit the range of substrate materials employed.
Furthermore, this assembling technique has a potential to integrate heterogeneous single crystalline nanowires
on the same substrate. Such integration of heterogeneous single crystalline objects on the same substrate is rather
difficult to be accomplished via conventional growth and lithography techniques. Previous studies have demonstrated that nanowires dispersed in solution can be aligned on the substrate by electric field1,2, magnetic field3–5,
fluid flow6–8, capillary force9–12,33,34, oil/water interface13,14 and others15–22,35. Among them, methods using lithographically defined patterns are promising for assembling heterogeneous nanowires due to the spatial controllability of patterns10–12,33,35. These methods require nanoscale patterns, which correspond to nanowire sizes. Thisrequirement essentially limits the available size range in the size selectivity due to the size limitation of lithography36,37. Since one of major advantages for nanowires is the size range beyond the limitation of lithography, thepositioning method for nanowires, whose size range is not limited by lithography, is highly desired.
This study proposes a size selective deposition technique and sequential alignment of nanowires by utilizing
micrometer scale hydrophilic/hydrophobic patterned substrate. We utilized nanowires dispersed within oil,which were preferentially deposited only at a water/oil interface onto the hydrophilic patterns. We found thenanoscale size selectivity of nanowires deposited onto micrometer scale hydrophilic patterns. This nanoscale size
selectivity by micrometer scale patterns can be extended to the sequential alignment of different sized nanowires
on the same substrate.

Results
Fig. 1a shows the schematic illustration of proposed method to exhibit the size selectivity of nanowires by utilizing
micrometer scale hydrophilic/hydrophobic patterned substrate. In this method, water is first blade-coated onto
the hydrophilic patterns of substrate. Before the water evaporates, Si nanowires dispersed within oil (1,4-dichlorSCIENTIFIC REPORTS | 4 : 5943 | DOI: 10.1038/srep05943

1www.nature.com/scientificreports

Figure 1 | (a) Schematic illustration of nanoscale size selective deposition of nanowires utilizing micrometer hydrophilic patterns. (b) Effect of height ofwater layer on the nanowire depositions on the hydrophilic patterns. Schematic illustration and calculated free energy data of Si nanowire (100 nm
diameter and 4.5 mm length) at oil/water interface were shown. The solid lines represent the possible free energy difference when the nanowire is adsorbed
from oil to oil/water interface. Z is the distance between the oil/water interface and the nanowire bottom in the water. (c) Normalized free energy gain data
as a function of height of water layer for nanowires with the diameters of 100 nm and 625 nm. The free energy values were normalized by the maximum
value of free energy gain. The inset shows the critical height as a function of nanowire diameter. The critical height is defined as the height of water layer
below which the free energy gain tends to decrease due to the geometrical limitation for the contact between nanowire and water. (d) Measured data of theheight of water layers when varying the hydrophilic pattern width. The data was averaged from each 10 measurements. The inset shows the microscopy
image of water droplets formed on the hydrophilic pattern.

obutane) is blade-coated onto the same substrate. During this coatingprocess, the oil dispersion comes into contact with the water layer on
the hydrophilic patterns, creating the water/oil interface. Nanowires
dispersed within oil are preferentially adsorbed only at such water/oil
interface to minimize Gibbs free energy of system13,38, as shown in thecalculation data of Fig. 1b and Supplementary Information-S1. The
key idea of the present method for the size selectivity of nanowires is
to utilize the nanoscale height variation of water layers formed onto
the micrometer scale hydrophilic patterns. As shown in Fig. 1b and c,
our free energy calculations predict the emergence of size selectivityof deposited nanowires on micrometer scale hydrophilic patterns
when the height of water layer is below around the radius of nanowires. This is due to the geometrical limitation for the contact
between nanowire and water layer. Fig. 1c shows the calculated freeenergy gain data when varying the height of water layer. The freeenergy gain tends to decrease below the critical height of water layer
hc, which is slightly lower than the radius of nanowires, as shown in
the inset of Fig. 1 (c). Thus, the size selective deposition of nanowires
onto the hydrophilic patterns might emerge if we can control theheight of water layer at the size scale of nanowire radius. In general,the height of water layer formed on micrometer scale hydrophilicpatterns is much lower than the width of patterns due to the wetting
nature39–41. Our measurements for the height of water layers demonstrated that the height values can be varied at nanoscale range when
SCIENTIFIC REPORTS | 4 : 5943 | DOI: 10.1038/srep05943

the pattern width is below 10 mm, as shown in Fig. 1d andSupplementary Information-S2. Thus, it might be possible to exhibit
the nanoscale size selectivity of nanowires by utilizing the nanoscaleheight variation of water layers formed onto the micrometer scalehydrophilic patterns.
Fig. 2a and b shows the typical dark field optical microscopy
images of aligned Si nanowires. In this experiment, the nanowire
diameter, the pattern size (width 3 length), the coating speed, thecoating cycles and temperature were 625 nm, 3 mm 3 10 mm,
10 mm/s, 100 and 20uC, respectively. The employed Si nanowires
were fabricated by metal-assisted chemical etching method42–44. In
Fig. 2a, the deposition probability of nanowires for a pattern was
98%. The deposition probability is defined as the number probabilityof patterns where the nanowire exists. Fig. 2c and 2d show the deposition probability of nanowires when varying the pattern width andthe nanowire diameter. For the experiments in Fig. 2c, the nanowires
with the diameter of 100 nm and 625 nm were used. As seen in
Fig. 2c, the deposition probability of nanowires with the diameterof 625 nm decreased from 100% to 2.7% when decreasing the pattern
width from 10 mm to 0.5 mm. On the other hand, the deposition
probability of nanowires with the diameter of 100 nm was kept tobe almost 100% even varying the width of patterns. For the experiments in Fig. 2d, the hydrophilic patterns with the widths of 2 mm
and 10 mm were employed. When increasing the nanowire diameters2www.nature.com/scientificreports

Figure 2 | (a) Typical dark field optical microscopy and (b) magnified images of aligned 625 nm diameter nanowire on 3 mm width of hydrophilicpatterns. (c) Deposition probability data of nanowires when varying hydrophilic pattern width. The data for nanowires with the diameters of 100 nm and625 nm were shown. (d) Deposition probability data of nanowires when varying nanowire diameters. The data for the hydrophilic pattern widths of 2 mm
and 10 mm were shown. The coating cycles are 20 for the experiments in Figure 2 (c) and (d).

from 100 nm to 625 nm for the constant width of pattern-2 mm, thedeposition probability decreased from 100% to 9.3%, as shown in
Fig. 2d. For the pattern width of 10 mm, the deposition probability ofnanowires was almost 100% independent of the nanowire diameter.
Thus these results of Fig. 2c and 2d clearly highlight the occurrence ofthe size selective deposition of nanowires using micrometer scalehydrophilic/hydrophobic patterned substrate.
Next, we examine what really causes the size selective deposition in
Fig. 2. If our present scenario based on the nanoscale height variationof water layer on the micrometer hydrophilic patterns is correct toexplain the present results, the evaporation events of the water layer
should play an important role on the observed nanowire depositions.
To validate the scenario, we intentionally varied the height of waterlayer during deposition processes by varying the temperature and theblade-coating speed for depositions. Fig. 3a and 3b show the effects oftemperatures and the blade-coating speeds on the deposition probability of nanowires. In these deposition experiments, the nanowires
with the diameter of 300 nm and the hydrophilic pattern width of
2 mm were employed. When decreasing the blade-coating speed, theinterval time between the water layer deposition and the oil layer
deposition increases. The longer interval time must promote theevaporation of water layers before depositing oil dispersion withnanowires. As seen in Fig. 3a, decreasing the blade-coating speed
resulted in the decrease of the deposition probability of nanowires.
When increasing the deposition temperature, the deposition probability of nanowires decreased, as shown in Fig. 3b. This is clearly due
to the enhancement of water layer evaporation via the increased
deposition temperature. Thus, these two data demonstrate the critical role of water layer on the deposition probability of nanowires.
Based on above size selective deposition phenomenon using
micrometer hydrophilic patterns, we demonstrate the sequentialalignment of heterogeneous nanowires on the substrate. Fig. 4ashows the schematic illustration how the sequential alignment ofdifferent sized nanowires can be performed. Since relatively large
sized nanowires cannot be deposited onto the shallow water layeron the hydrophilic patterns due to the above principle, sequential
SCIENTIFIC REPORTS | 4 : 5943 | DOI: 10.1038/srep05943

nanowire depositions for two different sized micrometer scale hydrophilic patterns might allow us to align selectively different sizednanowires only at the desired spatial locations. Here, we used
3 mm-width and 500 nm-width hydrophilic patterns. Two different
diameter sized nanowires (625 nm and 100 nm) were sequentiallydeposited onto the patterned substrate. Fig. 4b shows the optical
microscopy images of 1st deposition for nanowires of 625 nm diameter (left) and 2nd deposition for nanowires of 100 nm diameter(right). As clearly seen in the images, the two different sized nanowires were selectively deposited at each desired patterns. The deposition probabilities for the first and second depositions were . 97%
and . 98%, respectively. Interestingly, during the 2nd deposition,
the smaller nanowires were not deposited onto the patterns withpredeposited larger nanowires. The existence of nanowires at thepatterns seems to prevent the subsequent depositions of nanowires
at the water/oil interface. Presumably, the repulsion force between
nanowires and/or the decreased hydrophilicity due to the presence of
nanowires might cause such phenomena. Thus, we successfully
demonstrated the sequential alignment of different sized nanowires
on the substrate by applying the nanoscale size selective phenomenon using micrometer hydrophilic patterns. Since the present size
selective method utilizes the nanoscale height variation of waterlayer, the size range of selectivity could be further decreased bydecreasing and controlling the height of water layer.

Discussion
In summary, we report a size selective deposition and sequentialalignment of nanowires by utilizing micrometer scale hydrophilic/hydrophobic patterned substrate. Nanowires dispersed within oil
were preferentially deposited only at a water/oil interface onto thehydrophilic patterned area. The key idea to produce the nanoscale
size selectivity is to utilize the nanoscale height variation of waterlayer naturally formed onto the micrometer hydrophilic patterns.
We found that the deposited nanowire size was strongly limited by
micrometer width of hydrophilic patterns. Thus it was possible toexhibit the nanoscale size selectivity of nanowires by utilizing micro3

www.nature.com/scientificreports

Figure 3 | (a) Deposition probability data of nanowires when varying the blade coating speed at 20uC. (b) Deposition probability data of nanowires whenvarying the temperature for depositions with the blade-coating speed of 10 mm/s. In these deposition experiments, the nanowire diameter, thepattern size and the coating cycles were 300 nm, 2 mm 3 10 mm and 20, respectively.

meter scale hydrophilic patterns. Furthermore, we successfully
demonstrated the sequential alignment of different sized nanowires
on the same substrate by applying this size selectively phenomena.

Methods
Si Nanowires Fabrication. Si nanowires with the diameter ranged from 100 nm to625 nm were fabricated by metal-assisted chemical etching method using Au meshpatterns on Si substrate. See the fabrication details in Supplementary Information-S3.
The length of Si nanowires was controlled to be 4.5 mm.
Si Nanowires Surface Modification. Si nanowire surfaces were chemically modified
by 1% chloromethyl(trichloro)silane in a chloroform and hexadecane (154) solution
for 2 hours at room temperature. These chemically modified Si nanowires weredispersed into 1,4-dichlorobutane by sonication. The concentration of nanowires wasestimated to be 5.68 3 106/ml.
Hydrophilic/Hydrophobic Patterned Substrate Fabrication. The hydrophilic/hydrophobic patterns on the Si3N4/Si substrate were fabricated by conventional
photolithography. The patterned substrates were immersed into 1% 1H,1H,2H,2Hperfluorooctyl(trichloro)silane (FOTS) in perfluorooctane for 2 hours at room
temperature. After forming FOTS self-assemble layer on the substrate, the photoresist
patterns were removed by ultra-sonication in acetone, N,N-dimethylformamide andisopropanol. The widths of patterns were ranged from 0.5 to 10 mm. 4 3 4 cm
patterned substrate was used for blade-coating process.
Blade Coating Alignment Process. The blade coating was performed by using two
blades for Milli-Q water and 1,4-dichlorobutane with nanowires, sequentially. The

Figure 4 | (a) Schematic illustration of sequential alignment of different sized nanowires. (b) Dark field optical microscopy images of nanowirealignment. Left image shows the data for 1st blade-coating by nanowires with the diameter of 625 nm, and the right image shows the data for 2nd bladecoating by nanowires with the diameter of 100 nm. The sizes (width 3 length) of large and small patterns were 3 mm 3 8 mm and 500 nm 3 8 mm,
respectively. The coating cycles for 1st and 2nd blade-coatings were 100 and 10, respectively.
SCIENTIFIC REPORTS | 4 : 5943 | DOI: 10.1038/srep05943

4www.nature.com/scientificreports
distance between two blades was set to be 2 mm. During the blade-coating process,water was selectively deposited onto the hydrophilic patterns. 1,4-dichlorobutane
with nanowires was subsequently deposited onto the water layer formed on thehydrophilic patterns.
1. Duan, X. F., Huang, Y., Cui, Y., Wang, J. F. & Lieber, C. M. Indium phosphidenanowires as building blocks for nanoscale electronic and optoelectronic devices.
Nature 409, 66–69 (2001).
2. Freer, E. M., Grachev, O., Duan, X. F., Martin, S. & Stumbo, D. P. High-yield selflimiting single-nanowire assembly with dielectrophoresis. Nat. Nanotechnol. 5,
525–530 (2010).
3. Tanase, M. et al. Magnetic trapping and self-assembly of multicomponent
nanowires. J. Appl. Phys. 91, 8549–8551 (2002).
4. Hangarter, C. M. & Myung, N. V. Magnetic alignment of nanowires. Chem. Mater.
17, 1320–1324 (2005).
5. Hangarter, C. M., Rheem, Y., Yoo, B., Yang, E. H. & Myung, N. V. Hierarchicalmagnetic assembly of nanowires. Nanotechnology 18, 205305 (2007).
6. Huang, Y. et al. Logic gates and computation from assembled nanowire building
blocks. Science 294, 1313–1317 (2001).
7. Huang, Y., Duan, X. F., Wei, Q. Q. & Lieber, C. M. Directed assembly of onedimensional nanostructures into functional networks. Science 291, 630–633(2001).
8. Huang, Y., Duan, X. F. & Lieber, C. M. Nanowires for integrated multicolor
nanophotonics. Small 1, 142–147 (2005).
9. Huang, J. X., Fan, R., Connor, S. & Yang, P. D. One-step patterning of aligned
nanowire arrays by programmed dip coating. Angew. Chem. Int. Ed. 46,
2414–2417 (2007).
10. Kuemin, C., Nowack, L., Bozano, L., Spencer, N. D. & Wolf, H. Oriented Assemblyof Gold Nanorods on the Single-Particle Level. Adv. Funct. Mater. 22, 702–708(2012).
11. Zhou, X. Z., Zhou, Y., Ku, J. C., Zhang, C. & Mirkin, C. A. Capillary Force-Driven,
Large-Area Alignment of Multi-segmented Nanowires. ACS Nano 8, 1511–1516(2014).
12. Zhou, Y. et al. Shape-Selective Deposition and Assembly of Anisotropic
Nanoparticles. Nano Lett. 14, 2157–2161 (2014).
13. Nakagawa, T., Torii, H., Kawashima, T. & Saitoh, T. Controlled deposition ofsilicon nanowires on chemically patterned substrate by capillary force using a
blade-coating method. J. Phys. Chem. C 112, 5390–5396 (2008).
14. Arase, H. & Nakagawa, T. Interfacial-Energy-Controlled Deposition Technique ofMicrostructures Using Blade-Coating. J. Phys. Chem. B 113, 15278–15283 (2009).
15. Rao, S. G., Huang, L., Setyawan, W. & Hong, S. H. Large-scale assembly of carbon
nanotubes. Nature 425, 36–37 (2003).
16. Sharma, R., Lee, C. Y., Choi, J. H., Chen, K. & Strano, M. S. Nanometer
positioning, parallel alignment, and placement of single anisotropic nanoparticles
using hydrodynamic forces in cylindrical droplets. Nano Lett. 7, 2693–2700(2007).
17. Yu, G., Cao, A. & Lieber, C. M. Large-area blown bubble films of aligned
nanowires and carbon nanotubes. Nat. Nanotechnol. 2, 372–377 (2007).
18. Fan, Z. et al. Wafer-scale assembly of highly ordered semiconductor nanowire
arrays by contact printing. Nano Lett. 8, 20–25 (2008).
19. Sharma, R. & Strano, M. S. Centerline Placement and Alignment of Anisotropic
Nanotubes in High Aspect Ratio Cylindrical Droplets of Nanometer Diameter.
Adv. Mater. 21, 60–65 (2009).
20. Takahashi, T. et al. Monolayer Resist for Patterned Contact Printing of Aligned
Nanowire Arrays. J. Am. Chem. Soc. 131, 2102–2013 (2009).
21. Park, H. et al. High-density integration of carbon nanotubes via chemical selfassembly. Nat. Nanotechnol. 7, 787–791 (2012).
22. Yao, J., Yan, H. & Lieber, C. M. A nanoscale combing technique for the large-scaleassembly of highly aligned nanowires. Nat. Nanotechnol. 8, 329–335 (2013).
23. Kwiat, M., Cohen, S., Pevzner, A. & Patolsky, F. Large-scale ordered 1Dnanomaterials arrays: Assembly or not? Nano Today 8, 677–694 (2013).
24. Wang, M. C. P. & Gates, B. D. Directed assembly of nanowires. Mater. Today 12,
34–43 (2009).
25. Liu, X., Long, Y. Z., Liao, L., Duan, X. F. & Fan, Z. Y. Large-Scale Integration of
Semiconductor Nanowires for High-Performance Flexible Electronics. ACS Nano
6, 1888–1900 (2012).
26. Long, Y. Z., Yu, M., Sun, B., Gu, C. Z. & Fan, Z. Y. Recent advances in large-scaleassembly of semiconducting inorganic nanowires and nanofibers for electronics,
sensors and photovoltaics. Chem. Soc. Rev. 41, 4560–4580 (2012).
27. Morales, A. M. & Lieber, C. M. A laser ablation method for the synthesis of
crystalline semiconductor nanowires. Science 279, 208–211 (1998).

SCIENTIFIC REPORTS | 4 : 5943 | DOI: 10.1038/srep05943

28. Cui, Y., Wei, Q. Q., Park, H. K. & Lieber, C. M. Nanowire nanosensors for highly
sensitive and selective detection of biological and chemical species. Science 293,
1289–1292 (2001).
29. Wang, Y. W., Schmidt, V., Senz, S. & Gosele, U. Epitaxial growth of silicon
nanowires using an aluminium catalyst. Nat. Nanotechnol. 1, 186–189 (2006).
30. Nagashima, K. et al. Intrinsic Mechanisms of Memristive Switching. Nano Lett.
11, 2114–2118 (2011).
31. Zhuge, F. et al. Fundamental Strategy for Creating VLS Grown TiO2 Single
Crystalline Nanowires. J. Phys. Chem. C 116, 24367–24372 (2012).
32. Meng, G. et al. Impact of Preferential Indium Nucleation on Electrical
Conductivity of Vapor-Liquid-Solid Grown Indium-Tin Oxide Nanowires. J. Am.
Chem. Soc. 135, 7033–7038 (2013).
33. Lim, J. K. et al. Alignment Strategies for the Assembly of Nanowires with
Submicron Diameters. Small 6, 1736–1740 (2010).
34. Wang, Z. L. et al. One-Step Self-Assembly, Alignment, and Patterning of Organic
Semiconductor Nanowires by Controlled Evaporation of Confined Microfluids.
Angew. Chem. Int. Ed. 50, 2811–2815 (2011).
35. Nepal, D. et al. Control over Position, Orientation, and Spacing of Arrays of Gold
Nanorods Using Chemically Nanopatterned Surfaces and Tailored ParticleParticle-Surface Interactions. ACS Nano 6, 5693–5701 (2012).
36. Harriott, L. R. Limits of lithography. Proc. IEEE 89, 366–374 (2001).
37. Pease, R. F. & Chou, S. Y. Lithography and other patterning techniques for future
electronics. Proc. IEEE 96, 248–270 (2008).
38. Hu, L. F., Chen, M., Fang, X. S. & Wu, L. M. Oil-water interfacial self-assembly: anovel strategy for nanofilm and nanodevice fabrication. Chem. Soc. Rev. 41,
1350–1362 (2012).
39. Sundberg, M., Mansson, A. & Tagerud, S. Contact angle measurements byconfocal microscopy for non-destructive microscale surface characterization.
J. Colloid and Interf. Sci. 313, 454–460 (2007).
40. Checco, A., Cai, Y. G., Gang, O. & Ocko, B. M. High resolution non-contact AFM
imaging of liquids condensed onto chemically nanopatterned surfaces.
Ultramicroscopy 106, 703–708 (2006).
41. Soolaman, D. M. & Yu, H. Z. Water microdroplets on molecularly tailoredsurfaces: Correlation between wetting hysteresis and evaporation mode switching.
J. Phys. Chem. B 109, 17967–17973 (2005).
42. Huang, Z., Geyer, N., Werner, P., de Boor, J. & Goesele, U. Metal-Assisted
Chemical Etching of Silicon: A Review. Adv. Mater. 23, 285–308 (2011).
43. He, Y. et al. Crystal-Plane Dependence of Critical Concentration for Nucleation
on Hydrothermal ZnO Nanowires. J. Phys. Chem. C 117, 1197–1203 (2013).
44. Geyer, N. et al. Model for the Mass Transport during Metal-Assisted Chemical
Etching with Contiguous Metal Films As Catalysts. J. Phys. Chem. C 116,
13446–13451 (2012).

Acknowledgments
This study was supported by NEXT.

Author contributions
Y.H., K.N., M.K. and T.Y. designed this work and prepared the manuscript. The
experiments were carried out by Y.H., K.N., G.M., F.Z. and Y.H., K.N., M.K. G.M., F.Z., S.R.
X.L., T.K., T.Y. have analyzed the results and discussed the manuscript during the
preparation. All authors discussed the results and implications and commented on the
manuscript at all stages.

Additional information
Supplementary information accompanies this paper at http://www.nature.com/
scientificreports
Competing financial interests: The authors declare no competing financial interests.
How to cite this article: He, Y. et al. Nanoscale Size-Selective Deposition of Nanowires byMicrometer Scale Hydrophilic Patterns. Sci. Rep. 4, 5943; DOI:10.1038/srep05943 (2014).
This work is licensed under a Creative Commons Attribution 4.0 International
License. The images or other third party material in this article are included in thearticle’s Creative Commons license, unless indicated otherwise in the credit line; if
the material is not included under the Creative Commons license, users will need
to obtain permission from the license holder in order to reproduce the material. To
view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/

5