Superposed shear and compression of strong colloidal gels

Islam, M. M.; Lester, Daniel

doi:10.1122/8.0000258

Cited by 3 publications

(1 citation statement)

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“…These highly stressed regions can lead to localized yielding and plastic deformation of the material [44]. Load-bearing particulate aggregates undergo nonaffine deformation that induces buckling and accelerates material failure [45]. The brittle characteristic of mixed gelatin/Laponite gels under compression is expected to affect its performance in EBB as well.…”

Section: Macrorheological Characterization: Slip Shear-induced Fractu...mentioning

confidence: 99%

Targeted micro-heterogeneity in bioinks allows for 3D printing of complex constructs with improved resolution and cell viability

et al. 2023

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3D bioprinting is an evolving versatile technique for biomedical applications. Ideal bioinks have complex micro-environment that mimic human tissue, allow for good printing quality and provide high cell viability after printing. Here we present two strategies for enhancing gelatin-based bioinks heterogeneity on a 1-100µm length scale resulting in superior printing quality and high cell viability. A thorough spatial and micro-mechanical characterization of swollen hydrogel heterogeneity was done using Multiple Particle Tracking microrheology. When poly(vinyl alcohol) is added to homogeneous gelatin gels, viscous inclusions are formed due to micro-phase separation. This phenomenon leads to pronounced slip and superior printing quality of complex 3D constructs as well as high HepG2 and NHDF cell viability due to reduced shear damage during extrusion. Similar printability and cell viability results are obtained with gelatin/nanoclay composites. The formation of polymer/nanoclay clusters reduces the critical stress of gel fracture, which facilitates extrusion, thus enhancing printing quality and cell viability. Targeted introduction of micro-heterogeneities in bioinks through micro-phase separation is an effective technique for high resolution 3D printing of complex constructs with high cell viability. The size of the heterogeneities, however, has to be substantially smaller than the desired feature size in order to achieve good printing quality.

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Section: Macrorheological Characterization: Slip Shear-induced Fractu...mentioning

confidence: 99%

Targeted micro-heterogeneity in bioinks allows for 3D printing of complex constructs with improved resolution and cell viability

et al. 2023

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Micro-mechanical insights into the stress transmission in strongly aggregating colloidal gel

Man

Dagur

Roy

2023

The Journal of Chemical Physics

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Predicting the mechanical response of the soft gel materials under external deformation is of paramount importance in many areas, such as foods, pharmaceuticals, solid-liquid separations, cosmetics, aerogels and drug delivery.Most ofthe understanding of the elasticity of gel materials is based on the concept of fractal scaling with very little microscopicinsights.Previous experimental observations strongly suggest that the gel material loses the fractal correlations upondeformation and the range of packing fraction up to which the fractal scaling can be applied is very limited.So far, there is no clear understanding of the gel elasticity at high packing fraction and the correct length scale that governsits mechanical response. In this work, we undertake extensive numerical simulations to elucidate the different aspectsof stress transmission in the gel materials. We observe the existence of two percolating networks of compressive andtensile normal forces close to the gel point. We also find that the probability distribution for the compressive andtensile part normalized by their respective mean shows universal behavior irrespective of varied interaction potential,thermal energy and particle size distribution. We alsoidentify the critical internal state parameters such as mean normal force, force anisotropies and the average coordinationnumber and propose simple constitutive relations that relate the different components of the stress to the internal stateparameters.Our resultsstrongly demonstrate that the mechanical response of the gel system is governed mainly by the particle length scalephenomena with a complex interplay between compressive and tensile forces at the particle contact.

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