Shape and structural relaxation of colloidal tactoids

Almohammadi, Hamed; Khadem, Sayyed Ahmad; Bagnani, Massimo; Rey, Alejandro D.; Mezzenga, Raffaele

doi:10.1038/s41467-022-30123-y

Cited by 12 publications

(11 citation statements)

References 68 publications

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“…These results show similar relaxation behavior as in our recent work on artificially elongated tactoids (see Ref. 43 for detailed analysis). Furthermore, once formed, all tactoids are oriented in the flow direction, except for cholesteric amyloid fibrils tactoids with four or higher number of bands, which are orientated almost perpendicular to flow direction, a behavior whose underpinning physics is not entirely clear yet, calling for further investigation (see Fig.…”

Section: Resultssupporting

confidence: 88%

Disentangling kinetics from thermodynamics in heterogeneous colloidal systems

et al. 2023

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In Nucleation and Growth, the process by which most heterogeneous systems form, thermodynamics sets the asymptotic boundaries toward which the system must evolve, while kinetics tries to cope with it by imposing the transport rates. In all heterogeneous colloidal systems observed in nature, composition, shape, structure and physical properties result from the trade-off between thermodynamics and kinetics. Here we show, by carefully selecting colloidal systems and controlling phase separation in microfluidic devices, that it becomes possible to disentangle kinetics effects from thermodynamics. Using amyloids and nanocellulose filamentous colloids, we demonstrate that decoupling kinetics from thermodynamics in the phase separation process unveils new physical phenomena, such as orders of magnitude shorter timescales, a wider phase diagram, and structures that are not observable via conventional liquid-liquid phase separation. Our approach enables on-demand fabrication of multicomponent heterogeneous liquid crystals, enhancing their potential, and introducing original fundamental and technological directions in multicomponent structured fluids.

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Section: Resultssupporting

confidence: 88%

Disentangling kinetics from thermodynamics in heterogeneous colloidal systems

et al. 2023

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“…As evaporation proceeds, chiral nematic CNC aggregates with spherical shapes and fingerprint patterns, also called tactoids, form when the concentration is above a critical value. Tactoids’ growth, coalescence, and sediments resulted in a continuous anisotropic phase formed through a nucleation growth mechanism. − Anisotropic phases with planar, fingerprint, and mixed patterns are illustrated and imaged in Figure c,d, respectively. Gravity and interfacial tension at the isotropic–anisotropic interface are the primary driving forces for phase separation.…”

Section: Chirality Of Cnc Particles and Cnc Aggregatesmentioning

confidence: 99%

“…For instance, POM provides a robust system in which direct observation of chiral nematic CNC structures is possible. The existence and fusion of tactoids have been viewed under POM. , Using POM makes it possible to directly observe the ordering kinetics and phase transitions of CNC suspension . POM with a rotation stage was also used to determine the handedness of the liquid chiral CNCs assemblies .…”

Section: Chirality Of Cnc Particles and Cnc Aggregatesmentioning

confidence: 99%

Accelerating Cellulose Nanocrystal Assembly into Chiral Nanostructures

et al. 2023

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Cellulose nanocrystal (CNC) suspensions self-assembled into chiral nematic liquid crystals. This property has enabled the development of versatile optical materials with fascinating properties. Nevertheless, the scale-up production and commercial success of chiral nematic CNC superstructures face significant challenges. Fabrication of chiral nematic CNC nanostructures suffers from a ubiquitous pernicious trade-off between uniform chiral nematic structure and rapid self-assembly. Specifically, the chiral nematic assembly of CNCs is a time-consuming, spontaneous process that involves the organization of particles into ordered nanostructures as the solvent evaporates. This review is driven by the interest in accelerating chiral nematic CNC assembly and promoting a long-range oriented chiral nematic CNC superstructure. To start this review, the chirality origins of CNC and CNC aggregates are analyzed. This is followed by a summary of the recent advances in stimuli-accelerated chiral nematic CNC self-assembly procedures, including evaporation-induced self-assembly, continuous coating, vacuum-assisted self-assembly, and shear-induced CNC assembly under confinement. In particular, stimuli-induced unwinding, alignment, and relaxation of chiral nematic structures were highlighted, offering a significant link between the accelerated assembly approaches and uniform chiral nematic nanostructures. Ultimately, future opportunities and challenges for rapid chiral nematic CNC assembly are discussed for more innovative and exciting applications.

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“…In partial summary, simple extensions of the liquid crystal shape equation that include membrane elasticity generate morphology phase diagrams that include most of the observed cell shapes beyond the usual liquid crystal tactoids (Bagnani et al, 2018;Nyström et al, 2018;Gârlea et al, 2019;Li et al, 2020b; Almohammadi et al, 2022). Some dynamics simulation of selfassembly can be found in (Khayyatzadeh et al, 2015;Han et al, 2017;Fu and Abukhdeir, 2018).…”

Section: D Closed Surface Wrinkling: Droplets and Tactoidsmentioning

confidence: 99%

Pattern formation, structure and functionalities of wrinkled liquid crystal surfaces: A soft matter biomimicry platform

Wang

Servio

Rey

2023

Front. Soft. Matter

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This review presents an integrated theoretical and computational characterization and analysis of surface pattern formation in chiral and achiral liquid crystal self-assembly and the mechanical/optical/tribological/tissue engineering surface functionalities that emerge from various wrinkling processes. Strategies to target surface patterns include linear, non-linear, multidirectional and multiscale wrinkling phenomena. The focus of the review is to show the unique surface structure-functionalities that emerge from anisotropic liquid crystal soft matter, eliminating or reducing the need of aggressive solvents, extreme pressure/temperature conditions, erosion and other surface morphing approaches. The surface pattern formation theoretical-modelling- computational results are then connected and validated with actual biological surfaces that are considered solid liquid crystal analogues, such as exocuticles of insects, fish scales, and flowers. A unique feature of the in silico surface pattern formation platform used throughout this review is the generalized liquid crystal shape equation that includes surface anchoring elasticity, membrane elasticity, and stress loads from liquid crystals orientation gradients. Clear characterization of surface shapes, curvatures, roughness, that are behind surface functionalities are introduced and applied to strengthen validation of predictions with actual nature’s surfaces. Wrinkling scaling laws, and the dependence of material properties on morphing mechanisms are elucidated. The predictions capture very well the two-scale wrinkling patterns in tulips, wrinkling gradients that display water sensor capabilities, egg carton shapes in rose petals and their potential for cell alignment, and the ability to create surface roughness with targeted kurtosis and skewness to control and optimize friction and tribological functionalities. The results are summarized in terms of surface geometry (open or closed) mechanisms and phenomena (anchoring, membrane elasticity), material properties (anchoring coefficients, membrane bending modulus, Frank elasticity), wrinkling scales and scaling laws (amplitude, wave-lengths, skewness, kurtosis) and functionalities (optical iridescence, friction, wettability, structural color, curvature-driven cell alignment and differentiation). Taken together, the range of surface geometries and surface functionalities captured by the liquid crystal biomimetic in silico platform provides a foundation for future experimental green manufacturing pathways based on anisotropic soft matter.

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Shape and structural relaxation of colloidal tactoids

Cited by 12 publications

References 68 publications

Disentangling kinetics from thermodynamics in heterogeneous colloidal systems

Disentangling kinetics from thermodynamics in heterogeneous colloidal systems

Accelerating Cellulose Nanocrystal Assembly into Chiral Nanostructures

Pattern formation, structure and functionalities of wrinkled liquid crystal surfaces: A soft matter biomimicry platform

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