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Formation of three-dimensional (3D) Self-Assembled Clusters of Anisotropic Janus Particles in Microgravity

Jongmin Kim

Jongmin Kim

Department of Chemical Engineering and Applied Chemistry, Chungnam National UniversityDaejeon, Republic of Korea
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Kim, Jongmin
, 
Reya Ganguly

Reya Ganguly

Department of Chemical Engineering and Applied Chemistry, Chungnam National UniversityDaejeon, Republic of Korea
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Ganguly, Reya
, 
Jaesung Kim

Jaesung Kim

Department of Chemical Engineering and Applied Chemistry, Chungnam National UniversityDaejeon, Republic of Korea
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Kim, Jaesung
, 
Ronald J. Sicker

Ronald J. Sicker

USRA at NASA Glenn Research CenterCleveland, USA
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Sicker, Ronald J.
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Francis P. Chiaramonte

Francis P. Chiaramonte

USRA at NASA Glenn Research CenterCleveland, USA
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Chiaramonte, Francis P.
, 
William V. Meyer

William V. Meyer

USRA at NASA Glenn Research CenterCleveland, USA
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Meyer, William V.
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Catherine A. Frey

Catherine A. Frey

ZIN TechnologiesCleveland, USA
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Frey, Catherine A.
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John G. Eustace

John G. Eustace

ZIN TechnologiesCleveland, USA
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Eustace, John G.
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Deena M. Dombrosky

Deena M. Dombrosky

ZIN TechnologiesCleveland, USA
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Dombrosky, Deena M.
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Mark W. Pestak

Mark W. Pestak

Cleveland, USA
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Pestak, Mark W.
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Chang-Soo Lee

Chang-Soo Lee

Department of Chemical Engineering and Applied Chemistry, Chungnam National UniversityDaejeon, Republic of Korea
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Lee, Chang-Soo
  
16 ago 2024
Formation of three-dimensional (3D) Self-Assembled Clusters of Anisotropic Janus Particles in Microgravity's Cover Image
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Categoría del artículo: Research Note
Publicado en línea: 16 ago 2024
Páginas: 115 - 129
DOI: https://doi.org/10.2478/gsr-2024-0008
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© 2024 Jongmin Kim et al., published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Figure 1.

Two crucial design principles for Janus particles based on chemical and geometrical anisotropy, and expectation on possible degree of freedom for continuous growth controlled by the ratio between hydrophobic and hydrophilic parts of the Janus particles. (A) Chemical anisotropy of the Janus particle: Precise control of interparticle interaction involving hydrophobic interaction and hydrophilic repulsion. (B) Geometrical anisotropy of the Janus particle: The hydrophobic (red) and hydrophilic (blue) ratio of the Janus particles possibly affects the interaction between initially assembled structures and free Janus particles, allowing different degrees of freedom for continuous growth during the self-assembly. For example, a 3:7 ratio allows interaction with 1 or 2 more Janus particles, 5:5 with 2 or 3 more, and 7:3 with 3 or 4 more. The additional geometrical anisotropy in the form of a convex-top design plays a role by enabling hydrophobic interactions with minimal contact area, thereby supporting continuous growth.
Two crucial design principles for Janus particles based on chemical and geometrical anisotropy, and expectation on possible degree of freedom for continuous growth controlled by the ratio between hydrophobic and hydrophilic parts of the Janus particles. (A) Chemical anisotropy of the Janus particle: Precise control of interparticle interaction involving hydrophobic interaction and hydrophilic repulsion. (B) Geometrical anisotropy of the Janus particle: The hydrophobic (red) and hydrophilic (blue) ratio of the Janus particles possibly affects the interaction between initially assembled structures and free Janus particles, allowing different degrees of freedom for continuous growth during the self-assembly. For example, a 3:7 ratio allows interaction with 1 or 2 more Janus particles, 5:5 with 2 or 3 more, and 7:3 with 3 or 4 more. The additional geometrical anisotropy in the form of a convex-top design plays a role by enabling hydrophobic interactions with minimal contact area, thereby supporting continuous growth.

Figure 2.

Convex-top Janus particles with three different ratios (3:7, 5:5, 7:3) of hydrophobic and hydrophilic parts showing the geometrical anisotropy. (A) Schematic images and brightfield images showing uniformly controlled geometric aspects: the three different ratios (3:7, 5:5, 7:3) and the convex-top. In the inset images of the Janus particles, the hydrophobic parts are notably darker, while the hydrophilic parts appear brighter, highlighting the clear boundary between these distinct parts. (B) Quantitative analysis illustrating the geometrical anisotropy, ratios of the hydrophobic and hydrophilic parts of the convex-top Janus particles as designed (3:7, 5:5 and 7:3). Scale bars in all images are 30 μm.
Convex-top Janus particles with three different ratios (3:7, 5:5, 7:3) of hydrophobic and hydrophilic parts showing the geometrical anisotropy. (A) Schematic images and brightfield images showing uniformly controlled geometric aspects: the three different ratios (3:7, 5:5, 7:3) and the convex-top. In the inset images of the Janus particles, the hydrophobic parts are notably darker, while the hydrophilic parts appear brighter, highlighting the clear boundary between these distinct parts. (B) Quantitative analysis illustrating the geometrical anisotropy, ratios of the hydrophobic and hydrophilic parts of the convex-top Janus particles as designed (3:7, 5:5 and 7:3). Scale bars in all images are 30 μm.

Figure 3.

2D assembly of convex-top Janus particles under gravity. (A) The representative self-assembled 2D clusters and their type of pair configurations formed via self-assembly of each Janus particles (3:7, 5:5, 7:3). (B) Sequential time-lapse images showing the formation of the limited small dimer (N=2) staying at a similar position with a slight orientation change over time. This result demonstrates gravitational sedimentation severely interferes with the movement of particles as well as their self-assembly. (C) 2D mean squared displacement (MSD) of each of the convex-top Janus particles (3:7, 5:5, 7:3) in gravity. A slope (yellow) of the solid line divided by 4 yields the 2D translational diffusion coefficient of each convex-top Janus particle. Scale bars in the image showing the 7:3 Janus particle is 5 μm.
2D assembly of convex-top Janus particles under gravity. (A) The representative self-assembled 2D clusters and their type of pair configurations formed via self-assembly of each Janus particles (3:7, 5:5, 7:3). (B) Sequential time-lapse images showing the formation of the limited small dimer (N=2) staying at a similar position with a slight orientation change over time. This result demonstrates gravitational sedimentation severely interferes with the movement of particles as well as their self-assembly. (C) 2D mean squared displacement (MSD) of each of the convex-top Janus particles (3:7, 5:5, 7:3) in gravity. A slope (yellow) of the solid line divided by 4 yields the 2D translational diffusion coefficient of each convex-top Janus particle. Scale bars in the image showing the 7:3 Janus particle is 5 μm.

Figure 4.

3D assembly of convex-top Janus particles in microgravity. (A) The representative self-assembled 3D dimers (N=2) and their various multiaxial orientation pair configurations formed via self-assembly of each of the Janus particles (3:7, 5:5, 7:3). (B) Various forms of self-assembled 3D clusters such as spherical-like, densely packed, and linearly grown clusters that are thermodynamically favorable and considered an equilibrium state. (C) Sequential time-lapse images showing an initially assembled dimer (N=2) of the convex-top Janus particle and its continuous growth over time to tetramer (N=4). (D) 2D MSD of each convex-top Janus particle (3:7, 5:5, 7:3) in microgravity. A slope (yellow) of the solid line divided by 4 yields a 2D translational diffusion coefficient (Dt) of each convex-top Janus particle.
3D assembly of convex-top Janus particles in microgravity. (A) The representative self-assembled 3D dimers (N=2) and their various multiaxial orientation pair configurations formed via self-assembly of each of the Janus particles (3:7, 5:5, 7:3). (B) Various forms of self-assembled 3D clusters such as spherical-like, densely packed, and linearly grown clusters that are thermodynamically favorable and considered an equilibrium state. (C) Sequential time-lapse images showing an initially assembled dimer (N=2) of the convex-top Janus particle and its continuous growth over time to tetramer (N=4). (D) 2D MSD of each convex-top Janus particle (3:7, 5:5, 7:3) in microgravity. A slope (yellow) of the solid line divided by 4 yields a 2D translational diffusion coefficient (Dt) of each convex-top Janus particle.

Figure 5.

Temperature-dependent particle kinetics and their self-assembly. (A) The MSD of the Janus particles at each temperature (T≈20°C and T=60°C). A slope (red or blue) of the solid line divided by 4 yields the 2D translational diffusion coefficient of the 7:3 convex-top Janus particle at each temperature. The inset images show distinct 3D structures formed via self-assembly at each temperature: complex 3D clusters with smaller contact areas at 60°C and less complex 3D clusters with larger contact areas at 20°C. (B) Suggested behavior, interaction of the Janus particles, and 3D complex cluster formation at each temperature.
Temperature-dependent particle kinetics and their self-assembly. (A) The MSD of the Janus particles at each temperature (T≈20°C and T=60°C). A slope (red or blue) of the solid line divided by 4 yields the 2D translational diffusion coefficient of the 7:3 convex-top Janus particle at each temperature. The inset images show distinct 3D structures formed via self-assembly at each temperature: complex 3D clusters with smaller contact areas at 60°C and less complex 3D clusters with larger contact areas at 20°C. (B) Suggested behavior, interaction of the Janus particles, and 3D complex cluster formation at each temperature.

2D Translational diffusion coefficient (Dt) and collision frequency of the 7:3 convex-top Janus particle_

Conditions Temperature Thermal energy (kBT) Viscosity (η) Translational diffusion coefficient (Dt) Collision frequency (J)
°C K N·μm cP μm2/s sec−1
Gravity 23.5 296.65 4.097×10−15 0.899 3.773×10−2 0.054
Microgravity ≈20 ≈293.15 4.048×10−15 1.002 9.378×10−2 0.133
60 333.15 4.601×10−15 0.466 21.415×10−2 0.304

Theoretically estimated surface free energy of the Janus particles and their free energy of adhesion in water_

Polymeric surfaces Contact angle [°] Surface free energy components [mJ/m2]
Water DIM EG γs γsLW γs+ γs−
DDDMA (hydrophobic part) 108.33 46.60 56.42 36.15 36.15 1.11 a0
PEGDA-CEA-PETA (hydrophilic part) 35.95 41.25 45.44 38.98 38.98 a0 60.73
Water - - - b72.8 b21.8 b25.5 b25.5
Janus particles (Hydrophobic/Hydrophilic) Thermodynamic free energy of adhesion (ΔGad) [mJ/m2]
Hydrophilic-Hydrophilic part Hydrophobic-Hydrophobic part
DDDMA/PEGDA-CEA-PETA 50.46 −84.37
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