TY - JOUR
T1 - Structure-property relationship of a soft colloidal glass in simple and mixed flows
AU - Calabrese, Vincenzo
AU - Varchanis, Stylianos
AU - Haward, Simon J.
AU - Tsamopoulos, John
AU - Shen, Amy Q.
N1 - Funding Information:
The authors gratefully acknowledge the support of Okinawa Institute of Science and Technology Graduate University with subsidy funding from the Cabinet Office, Government of Japan. S.J.H. and A.Q.S. also acknowledge financial support from the Japanese Society for the Promotion of Science (JSPS, Grant Nos. 18K03958, 18H01135, and 21K03884) and the Joint Research Projects (JRPs) supported by the JSPS and the Swiss National Science Foundation (SNSF). J.T. also acknowledge financial support from the Hellenic Foundation of Research and Innovation (HFRI, Grant No. FM17-2309).
Publisher Copyright:
© 2021 The Author(s)
PY - 2021/11
Y1 - 2021/11
N2 - Hypothesis: Under specific conditions, rod-like cellulose nanocrystals (CNC) can assemble into structurally ordered soft glasses (SGs) with anisotropy that can be controlled by applying shear. However, to achieve full structural control of SGs in real industrial processes, their response to mixed shear and extensional kinematics needs to be determined. We hypothesise that by knowing the shear rheology of the CNC-based soft glass and adopting a suitable constitutive model, it is possible to predict the structure-property relationship of the SG under mixed flows. Experiments: We use an aqueous suspension with 2 wt% CNC at 25 mM NaCl to form a structurally ordered SG composed of a CNC network containing nematic domains. We combine rheometry and microfluidic experiments with numerical simulations to study the flow properties of the SG in shear, extension, and mixed flow conditions. Extensional flow is investigated in the Optimised Shape Cross-slot Extensional Rheometer (OSCER), where the SG is exposed to shear-free planar elongation. Mixed flow kinematics are investigated in a benchmark microfluidic cylinder device (MCD) where the SG flows past a confined cylinder in a microchannel. Findings: The SG in the MCD displays a velocity overshoot (negative wake) and a pronounced CNC alignment downstream of the cylinder. Simulations using the thixotropic elasto-visco-plastic (TEVP) model yield near quantitative agreement of the velocity profiles in simple and mixed flows and capture the structural fingerprint of the material. Our results provide a comprehensive link between the structural behaviour of a CNC-based SG and its mechanistic properties, laying foundations for the development of functional, built-to-order soft materials.
AB - Hypothesis: Under specific conditions, rod-like cellulose nanocrystals (CNC) can assemble into structurally ordered soft glasses (SGs) with anisotropy that can be controlled by applying shear. However, to achieve full structural control of SGs in real industrial processes, their response to mixed shear and extensional kinematics needs to be determined. We hypothesise that by knowing the shear rheology of the CNC-based soft glass and adopting a suitable constitutive model, it is possible to predict the structure-property relationship of the SG under mixed flows. Experiments: We use an aqueous suspension with 2 wt% CNC at 25 mM NaCl to form a structurally ordered SG composed of a CNC network containing nematic domains. We combine rheometry and microfluidic experiments with numerical simulations to study the flow properties of the SG in shear, extension, and mixed flow conditions. Extensional flow is investigated in the Optimised Shape Cross-slot Extensional Rheometer (OSCER), where the SG is exposed to shear-free planar elongation. Mixed flow kinematics are investigated in a benchmark microfluidic cylinder device (MCD) where the SG flows past a confined cylinder in a microchannel. Findings: The SG in the MCD displays a velocity overshoot (negative wake) and a pronounced CNC alignment downstream of the cylinder. Simulations using the thixotropic elasto-visco-plastic (TEVP) model yield near quantitative agreement of the velocity profiles in simple and mixed flows and capture the structural fingerprint of the material. Our results provide a comprehensive link between the structural behaviour of a CNC-based SG and its mechanistic properties, laying foundations for the development of functional, built-to-order soft materials.
KW - Anisotropic soft materials
KW - Cellulose nanocrystals
KW - Complex flows
KW - Flow past a cylinder
KW - Liquid crystal
KW - Microfluidics
KW - Negative wake
KW - Plasticity
KW - Shear banding
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U2 - 10.1016/j.jcis.2021.05.103
DO - 10.1016/j.jcis.2021.05.103
M3 - Review article
C2 - 34126412
AN - SCOPUS:85109001576
SN - 0021-9797
VL - 601
SP - 454
EP - 466
JO - Journal of Colloid And Interface Science
JF - Journal of Colloid And Interface Science
ER -