Droplets of cellulose nanocrystal suspensions on drying give iridescent 3-D “coffee-stain” rings

Mu, Xiaoyue; Gray, Derek G.

doi:10.1007/s10570-015-0569-3

Cited by 107 publications

(93 citation statements)

References 11 publications

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“…The heights of steps and cracks are shown in the X and Y profiles across the film (Figure 17) are of the order of 2 μm, which is much smaller than the >50 μm height difference previously observed at the edge of droplets with pinned contact lines [16]. However, the profilometry shows that the outer edge of each step is also raised, suggesting that a minor “coffee-stain effect” is also occurring during evaporation.…”

Section: Resultsmentioning

confidence: 73%

Chiral Nematic Structure of Cellulose Nanocrystal Suspensions and Films; Polarized Light and Atomic Force Microscopy

Gray

2015

Materials

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101

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Cellulosic liquid crystalline solutions and suspensions form chiral nematic phases that show a rich variety of optical textures in the liquid crystalline state. These ordered structures may be preserved in solid films prepared by evaporation of solvent or suspending medium. Film formation from aqueous suspensions of cellulose nanocrystals (CNC) was investigated by polarized light microscopy, optical profilometry and atomic force microscopy (AFM). An attempt is made to interpret qualitatively the observed textures in terms of the orientation of the cellulose nanocrystals in the suspensions and films, and the changes in orientation caused by the evaporative process. Mass transfer within the evaporating droplet resulted in the formation of raised rings whose magnitude depended on the degree of pinning of the receding contact line. AFM of dry films at short length scales showed a radial orientation of the CNC at the free surface of the film, along with a radial height variation with a period of approximately P/2, ascribed to the anisotropic shrinkage of the chiral nematic structure.

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Section: Resultsmentioning

confidence: 73%

Chiral Nematic Structure of Cellulose Nanocrystal Suspensions and Films; Polarized Light and Atomic Force Microscopy

Gray

2015

Materials

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101

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“…The coffee‐ring effect can be suppressed by addition of a nonvolatile additive, e.g., glucose, as shown in the right‐hand photograph and profile. Reproduced with permission . Copyright 2015, Springer Netherlands.…”

Section: The Role Of Geometrymentioning

confidence: 99%

“…On untreated glass or acrylic substrates, the higher evaporation rate near the edge generates an outward radial capillary flow inside the drop. This causes accumulation of nanorods at the edge and pinning of the contact line, resulting in a ring‐shaped deposit often referred to as a coffee ring stain (Figure b) . This radial flow also induces shear alignment that can disrupt the cholesteric order and cause linear birefringence.…”

Section: The Role Of Geometrymentioning

confidence: 99%

The Self‐Assembly of Cellulose Nanocrystals: Hierarchical Design of Visual Appearance

et al. 2017

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By controlling the interaction of biological building blocks at the nanoscale, natural photonic nanostructures have been optimized to produce intense coloration. Inspired by such biological nanostructures, the possibility to design the visual appearance of a material by guiding the hierarchical self‐assembly of its constituent components, ideally using natural materials, is an attractive route for rationally designed, sustainable manufacturing. Within the large variety of biological building blocks, cellulose nanocrystals are one of the most promising biosourced materials, primarily for their abundance, biocompatibility, and ability to readily organize into photonic structures. Here, the mechanisms underlying the formation of iridescent, vividly colored materials from colloidal liquid crystal suspensions of cellulose nanocrystals are reviewed and recent advances in structural control over the hierarchical assembly process are reported as a toolbox for the design of sophisticated optical materials.

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“…The formation of the chiral nematic phase of the CNCs can also be affected by the presence of organic molecules, such as glucose and polymers. More recently, Yao et al[34a] observed the influence of poly(ethylene glycol) (PEG) on the structural color of CNCs films.…”

Section: Cellulose‐based Systems Mimicking the Cuticle Photonic Strucmentioning

confidence: 99%

Cellulose‐Based Biomimetics and Their Applications

et al. 2018

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Nature has been producing cellulose since long before man walked the surface of the earth. Millions of years of natural design and testing have resulted in cellulose-based structures that are an inspiration for the production of synthetic materials based on cellulose with properties that can mimic natural designs, functions, and properties. Here, five sections describe cellulose-based materials with characteristics that are inspired by gratings that exist on the petals of the plants, structurally colored materials, helical filaments produced by plants, water-responsive materials in plants, and environmental stimuli-responsive tissues found in insects and plants. The synthetic cellulose-based materials described herein are in the form of fibers and films. Fascinating multifunctional materials are prepared from cellulose-based liquid crystals and from composite cellulosic materials that combine functionality with structural performance. Future and recent applications are outlined.

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Droplets of cellulose nanocrystal suspensions on drying give iridescent 3-D “coffee-stain” rings

Cited by 107 publications

References 11 publications

Chiral Nematic Structure of Cellulose Nanocrystal Suspensions and Films; Polarized Light and Atomic Force Microscopy

Chiral Nematic Structure of Cellulose Nanocrystal Suspensions and Films; Polarized Light and Atomic Force Microscopy

The Self‐Assembly of Cellulose Nanocrystals: Hierarchical Design of Visual Appearance

Cellulose‐Based Biomimetics and Their Applications

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