Assembly and manipulation of responsive and flexible colloidal structures by magnetic and capillary interactions

Basu, Ashoke Kumar; Okello, Lilian B.; Castellanos, Natasha Morales; Roh, Sangchul; Velev, Orlin D.

doi:10.1039/d3sm00090g

Cited by 7 publications

(2 citation statements)

References 211 publications

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“…In addition to the viscosity and surface tension of the evaporating droplets, [ 51,52 ] physicochemical characteristics such as different kinds of particle interactions, [ 53,54 ] especially capillary interaction, [ 55 ] are of great importance when it comes to determining the final deposition pattern. As alginate chains are cross‐linked with Ca 2+ , water‐soluble SA turns into an insoluble gel after CaCl 2 treatment.…”

Section: Resultsmentioning

confidence: 99%

Deposition Patterns of Evaporating Sodium Alginate Sessile Droplets Cross‐Linked by Calcium Chloride

Biglari,

Saberi,

Issakhani

et al. 2023

Macro Materials & Eng

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Controllable patterning of bio‐compatible polymers in the presence of a cross‐linker in evaporating bi‐dispersed colloidal drops is of critical importance in functional coatings, bioprinting, and food packaging. This study investigates the effect of calcium chloride and sodium alginate concentration on the evaporative deposition and elemental distribution of dried‐out patterns. Different concentrations of alginate and salt in aqueous solutions are deposited on clean glass substrates to gain a deeper understanding of the final structures. Overall, the results indicate that changing the concentrations of sodium alginate and calcium chloride can significantly alter the elemental distribution and deposition uniformity of the final patterns. The modifications in relative concentration alter the physicochemical characteristics of the solution, resulting in significant changes in the pinning time and contact angle of the droplets that correspond to the alteration of the colloidal size and concentration, ultimately resulting in significant differences in deposition patterns. The dried‐out patterns are categorized based on their structures and mechanisms (crystallization, sedimentation, and adsorption) controlling the evaporative deposition, and then justified based on the competitive effects of cross‐linking, crystallization, and evaporation‐driven flows. Using scanning electron microscopy and energy‐dispersive X‐ray spectroscopy, the elemental distribution of dried‐out patterns is also mapped to substantiate the discussion made.

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Section: Resultsmentioning

confidence: 99%

Deposition Patterns of Evaporating Sodium Alginate Sessile Droplets Cross‐Linked by Calcium Chloride

Biglari,

Saberi,

Issakhani

et al. 2023

Macro Materials & Eng

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“…The self-assembly of colloidal particles has emerged as a robust method to fabricate highly ordered structures composed of nanoscale building blocks of different sizes, shapes and compositions. − Such assembled superstructures can help in the creation of advanced functional materials with tunable properties. − The assembly of magnetic particles originates and can be controlled by the dipole–dipole interactions between the particles in a magnetic field. − These interactions are directional in nature and lead to the formation of out-of-equilibrium superstructures, which otherwise would not form in nonmagnetic particle systems. − Field-directed assembly has major advantages in that it is robust and contact-free. This allows the assembly to be controlled from outside the system without the manipulation of the experimental conditions such as temperature, pH and solvent composition. − The magnetic dipole–dipole interactions can be attractive or repulsive, based on the angle between the field and the dipoles, imparting significant freedom to the design of experiments.…”

Section: Introductionmentioning

confidence: 99%

Spatially Confined Assembly and Immobilization of Hierarchical Nanoparticle Architectures inside Microdroplets in Magnetic Fields

Basu,

Clary,

Tracy

et al. 2024

ACS Nano

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Magnetic field-directed colloidal interactions offer facile tools for assembly of structures that range from linear chains to multidimensional hierarchical architectures. While the field-driven assembly of colloidal particles has commonly been investigated in unbounded media, a knowledge gap remains concerning such assembly in confined microenvironments. Here, we investigate how confinement of ferromagnetic nanoparticles in microspheres directs their magnetic assembly into hierarchical architectures. Microdroplets from polydimethylsiloxane (PDMS) liquid precursor containing dispersed iron oxide magnetic nanoparticles (MNPs) were placed in a static magnetic field leading to the formation of organized assemblies inside the host droplets. By changing the MNP concentrations, we revealed a sequence of microstructures inside the droplets, ranging from linear chains at a low MNP loading, transitioning to a combination of chains and networked bundles, to solely 3D bundles at high MNP loading. These experimental results were analyzed with the aid of COMSOL simulations where we calculated the potential energy to identify the preferred assembly conformations. The chains at high MNP loading minimized their energy by aggregating laterally to form bundles with their MNP dipoles being out-ofregistry. We cured these PDMS droplets to immobilize the assemblies by forming soft microbeads. These microbeads constitute an "interaction toolbox" with different magnetic macroscale responses, which are governed by the structuring of the MNPs and their magnetic polarizability. We show that thanks to their ability to rotate by field-induced torque under a rotating field, these microbeads can be employed in applications such as optical modulators and microrollers.

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Magnetically Responsive Optical Modulation: from Anisotropic Nanostructures to Emerging Applications

Li,

et al. 2023

Adv Funct Materials

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Magnetically responsive optical modulation has emerged as a promising application in various fields such as smart windows, anti‐counterfeiting, and colorimetric sensors, due to its unique advantages in remote and nondestructive control, as well as precise and high‐contrast response. Compared to isotropic counterparts, anisotropic magnetic nanostructures (AMNs) take advantage of the interplay among magnetic dipoles, magnetocrystalline anisotropy, shape anisotropy, and crystal facets to control diverse dimensions of light propagation. By manipulating frequency, amplitude, polarization, and plasmonic resonance, AMNs can provide a variety of functional applications. A comprehensive overview of recent developments in optical modulation based on AMNs with a focus on their emerging applications and design strategies is presented. It starts with a brief introduction of typical AMN building blocks, highlighting various optical modulation modes, including tunable transmission, diffraction, polarization, and plasmonic resonance. The primary focus is to discuss design strategies for various applications, i.e., smart windows, anti‐counterfeiting labels, colorimetric sensors, and multifunctional‐driven devices. It concludes with the challenges and perspectives for magneto‐optical modulation based on anisotropic structures. Overall, this review provides in‐depth insight into building blocks, magnetic modulation strategies, and optical property modulation of AMNs, thereby accelerating practical applications of these structures in functional devices.

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Assembly and manipulation of responsive and flexible colloidal structures by magnetic and capillary interactions

Abstract: The long-ranged interactions induced by magnetic fields and capillary forces in multiphasic fluid-particle systems facilitate the assembly of a rich variety of colloidal structures and materials. We review here the...

Cited by 7 publications

References 211 publications

Deposition Patterns of Evaporating Sodium Alginate Sessile Droplets Cross‐Linked by Calcium Chloride

Deposition Patterns of Evaporating Sodium Alginate Sessile Droplets Cross‐Linked by Calcium Chloride

Spatially Confined Assembly and Immobilization of Hierarchical Nanoparticle Architectures inside Microdroplets in Magnetic Fields

Magnetically Responsive Optical Modulation: from Anisotropic Nanostructures to Emerging Applications

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