Multi-axis alignment of Rod-like cellulose nanocrystals in drying droplets

Pritchard, Cailean Q.; Navarro, Fernando; Roman, Maren; Bortner, Michael J.

doi:10.1016/j.jcis.2021.06.069

Cited by 22 publications

(22 citation statements)

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“…237 The Marangoni effect is the particle transfer along an interface between two phases due to a gradient of the surface tension. In 2009, 238 authors published the first explanation of the coffeering phenomena for cellulose nanocrystal suspensions. Using time-resolved polarized light microscopy, the components that result in the formation of tangential and radial alignments are discovered.…”

Section: Acs Foodmentioning

confidence: 99%

“…While AFM could distinguish the orientations of the particles and the surface of CNC formed films, optics can only see the actual average alignment of the mass. Due to dust grains obscuring particles direction 238 on the coffee-ring surface, slight circumferential realignment was not visible with polarized light microscopy. Particle orientations can also be achieved by vertically dipping a substrate in a suspension and lifting the plate out, 239 as shown in Figure 7c.…”

Section: Surface Modification and Orientation Of Cncsmentioning

confidence: 99%

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Cellulose Nanocrystals Examined by Atomic Force Microscopy: Applications and Fundamentals

Moud

2022

ACS Food Sci. Technol.

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Cellulose nanocrystals (CNCs) are nanoscale particles with huge surface areas, excellent mechanical properties, and the ability to develop tunable surface chemistry, thus allowing them to be mixed into a wide range of matrices. Using atomic force microscopy (AFM), we highlight recent developments in the microstructural characterization of CNC particles in various shapes at both particle and organization scales. Considering new uses for CNC suspensions and gels and given the considerable potential of CNC-based products in medicinal, energy, cosmetics, filtration, and food applications, leveraging existing state-of-the-art characterization technologies such as AFM to improve CNC-produced properties cannot be ruled out. AFM may be used as a probe to disclose more intimate information about CNCs and can show modulus, size, and morphology in comparison to other characterization tools. AFM based on the literature review here was found to be a good assessment tool to verify the state of interaction, the adhesion strength of certain particles or chemicals, and the mechanical properties of CNCs. Thus, in tandem with other technologically advanced characterization tools, knowledge provided here for proper assessment of CNCs is necessary. Based on the AFM application currently widespread on CNCs, it appears that more research efforts are needed to provide additional cues regarding CNC individual states or the organized state (isotropic or liquid crystalline) for future sustainable, ecofriendly product designs based on CNCs.

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Section: Acs Foodmentioning

confidence: 99%

Section: Surface Modification and Orientation Of Cncsmentioning

confidence: 99%

Cellulose Nanocrystals Examined by Atomic Force Microscopy: Applications and Fundamentals

Moud

2022

ACS Food Sci. Technol.

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“…In the absence of a container, a drop of CNC suspension will spread across a hydrophilic substrate to reach an equilibrium shape, which is governed by a combination of surface tension and substrate chemistry. Upon drying, the greater evaporation rate at the edge of the drop generates an outward radial capillary flow that leads to the accumulation and deposition of CNCs near the contact line . This so-called “coffee-ring effect” disrupts self-assembly and causes a significant color-shift across the microfilm profile .…”

Section: Structurally Colored Films Via Colloidal Self-assemblymentioning

confidence: 99%

Bioinspired Photonic Materials from Cellulose: Fabrication, Optical Analysis, and Applications

et al. 2023

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Metrics & MoreArticle RecommendationsCONSPECTUS: Polysaccharides are a class of biopolymers that are widely exploited in living organisms for a diversity of applications, ranging from structural reinforcement to energy storage. Among the numerous types of polysaccharides found in the natural world, cellulose is the most abundant and widespread, as it is found in virtually all plants. Cellulose is typically organized into nanoscale crystalline fibrils within the cell wall to give structural integrity to plant tissue. However, in several species, such fibrils are organized into helicoidal nanostructures with a periodicity comparable to visible light (i.e., in the range 250−450 nm), resulting in structural coloration. As such, when taking bioinspiration as a design principle, it is clear that helicoidal cellulose architectures are a promising approach to developing sustainable photonic materials. Different forms of cellulose-derived materials have been shown to produce structural color by exploiting self-assembly processes. For example, crystalline nanoparticles of cellulose can be extracted from natural sources, such as cotton or wood, by strong acid hydrolysis. Such "cellulose nanocrystals" (CNCs) have been shown to form colloidal suspensions in water that can spontaneously self-organize into a cholesteric liquid crystal phase, mimicking the natural helicoidal architecture. Upon drying, this nanoscale ordering can be retained into the solid state, enabling the specific reflection of visible light. Using this approach, colors from across the entire visible spectrum can be produced, alongside striking visual effects such as iridescence or a metallic shine. Similarly, polymeric cellulose derivatives can also organize into a cholesteric liquid crystal. In particular, edible hydroxypropyl cellulose (HPC) is known to produce colorful mesophases at high concentrations in water (ca. 60−70 wt %). This solution state behavior allows for interesting visual effects such as mechanochromism (enabling its use in low-cost colorimetric pressure or strain sensors), while trapping the structure into the solid state enables the production of structurally colored films, particles and 3D printed objects.In this article, we summarize the state-of-the-art for CNC and HPC-based photonic materials, encompassing the underlying selfassembly processes, strategies to design their photonic response, and current approaches to translate this burgeoning green technology toward commercial application in a wide range of sectors, from packaging to cosmetics and food. This overview is supported by a summary of the analytical techniques required to characterize these photonic materials and approaches to model their optical response. Finally, we present several unresolved scientific questions and outstanding technical challenges that the wider community should seek to address to develop these sustainable photonic materials.

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“…Despite extensive literature on the drying dynamics and evaporative self-assembly in droplets of colloids with particle aspect ratios on the order of 10 0 –10 1 (refs and − ), little is currently known about droplets containing rod-like colloids with aspect ratios as high as 10 2 or more. Such filamentous colloids exhibit liquid crystalline phases if the solution is up-concentrated above Onsager binodal branches .…”

Section: Introductionmentioning

confidence: 99%

Evaporation-Driven Liquid–Liquid Crystalline Phase Separation in Droplets of Anisotropic Colloids

Almohammadi

Mezzenga

2023

ACS Nano

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Drying a colloidal droplet involves complex physics that is often accompanied by evaporation-induced concentration gradients inside of the droplet, offering a platform for fundamental and technological opportunities, including self-assembly, thin film deposition, microfabrication, and DNA stretching. Here, we investigate the drying, liquid crystalline structures, and deposit patterns of colloidal liquid crystalline droplets undergoing liquid–liquid crystalline phase separation (LLCPS) during evaporation. We show that evaporation-induced progressive up-concentration inside the drying droplets makes it possible to cross, at different speeds, various thermodynamic stability states in solutions of amyloid fibril rigid filamentous colloids, thus allowing access to both metastable states, where phase separation occurs via nucleation and growth, as well as to unstable states, where phase separation occurs via the more elusive spinodal decomposition, leading to the formation of liquid crystalline microdroplets (or tactoids) of different shapes. We present the tactoids “phase diagram” as a function of the position within the droplet and elucidate their hydrodynamics. Furthermore, we demonstrate that the presence of the amyloid fibrils not only does not enhance the pinning behavior during droplet evaporation but also slightly suppresses it, thus minimizing the coffee-ring effect. We observed that microsize domains with cholesteric structure emerge in the drying droplet close to the droplet’s initial edge, yet such domains are not connected to form a uniform cholesteric dried film. Finally, we demonstrate that a fully cholesteric dried layer can be generated from the drying droplets by regulating the kinetics of the evaporation process.

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Multi-axis alignment of Rod-like cellulose nanocrystals in drying droplets

Cited by 22 publications

References 44 publications

Cellulose Nanocrystals Examined by Atomic Force Microscopy: Applications and Fundamentals

Cellulose Nanocrystals Examined by Atomic Force Microscopy: Applications and Fundamentals

Bioinspired Photonic Materials from Cellulose: Fabrication, Optical Analysis, and Applications

Evaporation-Driven Liquid–Liquid Crystalline Phase Separation in Droplets of Anisotropic Colloids

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