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

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

Gravitational and Space Research
Volume 12 (2024): Issue 1 (January 2024)
By: Jongmin Kim,  Reya Ganguly,  Jaesung Kim,  Ronald J. Sicker,  Francis P. Chiaramonte,  William V. Meyer,  Catherine A. Frey,  John G. Eustace,  Deena M. Dombrosky,  Mark W. Pestak and  Chang-Soo Lee  
Open Access
|Aug 2024

Figures & Tables

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_

ConditionsTemperatureThermal energy (kBT)Viscosity (η)Translational diffusion coefficient (Dt)Collision frequency (J)
°CKN·μmcPμm2/ssec−1
Gravity23.5296.654.097×10−150.8993.773×10−20.054
Microgravity≈20≈293.154.048×10−151.0029.378×10−20.133
60333.154.601×10−150.46621.415×10−20.304

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

Polymeric surfacesContact angle [°]Surface free energy components [mJ/m2]
WaterDIMEGγsγsLWγs+γs−
DDDMA (hydrophobic part)108.3346.6056.4236.1536.151.11a0
PEGDA-CEA-PETA (hydrophilic part)35.9541.2545.4438.9838.98a060.73
Water---b72.8b21.8b25.5b25.5
Janus particles (Hydrophobic/Hydrophilic)Thermodynamic free energy of adhesion (ΔGad) [mJ/m2]
Hydrophilic-Hydrophilic partHydrophobic-Hydrophobic part
DDDMA/PEGDA-CEA-PETA50.46−84.37
DOI: https://doi.org/10.2478/gsr-2024-0008 | Journal eISSN: 2332-7774
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Language: English
Page range: 115 - 129
Published on: Aug 16, 2024
Published by: American Society for Gravitational and Space Research
In partnership with: Paradigm Publishing Services
Publication frequency: 2 issues per year
Keywords:
Anisotropic particles,
Microgravity,
Self-assembly,
Janus particles,
directional interaction
Related subjects:
Life sciences,
Life sciences, other,
Materials sciences,
Materials sciences, other,
Physics,
Physics, other

© 2024 Jongmin Kim, Reya Ganguly, Jaesung Kim, Ronald J. Sicker, Francis P. Chiaramonte, William V. Meyer, Catherine A. Frey, John G. Eustace, Deena M. Dombrosky, Mark W. Pestak, Chang-Soo Lee, published by American Society for Gravitational and Space Research
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

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