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Dynamics of Cellulose Nanocrystal Alignment during 3D Printing.
Journal article

Dynamics of Cellulose Nanocrystal Alignment during 3D Printing.

  • Hausmann MK Complex Materials, Department of Materials , ETH Zürich , 8093 Zürich , Switzerland.
  • Rühs PA Complex Materials, Department of Materials , ETH Zürich , 8093 Zürich , Switzerland.
  • Siqueira G Complex Materials, Department of Materials , ETH Zürich , 8093 Zürich , Switzerland.
  • Läuger J Anton Paar Germany GmbH , Helmuth-Hirth-Strasse 6 , D-73760 Ostfildern , Germany.
  • Libanori R Complex Materials, Department of Materials , ETH Zürich , 8093 Zürich , Switzerland.
  • Zimmermann T Applied Wood Materials Laboratory , Empa, Swiss Federal Laboratories for Materials Science and Technology , 8600 Dübendorf , Switzerland.
  • Studart AR Complex Materials, Department of Materials , ETH Zürich , 8093 Zürich , Switzerland.
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  • 2018-07-06
Published in:
  • ACS nano. - 2018
3D printing
alignment
birefringence
cellulose nanocrystals
direct ink writing
polarized light
rheology
shear stress
English The alignment of anisotropic particles during ink deposition directly affects the microstructure and properties of materials manufactured by extrusion-based 3D printing. Although particle alignment in diluted suspensions is well described by analytical and numerical models, the dynamics of particle orientation in the highly concentrated inks typically used for printing via direct ink writing (DIW) remains poorly understood. Using cellulose nanocrystals (CNCs) as model building blocks of increasing technological relevance, we study the dynamics of particle alignment under the shear stresses applied to concentrated inks during DIW. With the help of in situ polarization rheology, we find that the time period needed for particle alignment scales inversely with the applied shear rate and directly with the particle concentration. Such dependences can be quantitatively described by a simple scaling relation and qualitatively interpreted in terms of steric and hydrodynamic interactions between particles at high shear rates and particle concentrations. Our understanding of the alignment dynamics is then utilized to estimate the effect of shear stresses on the orientation of particles during the printing process. Finally, proof-of-concept experiments show that the combination of shear and extensional flow in 3D printing nozzles of different geometries provides an effective means to tune the orientation of CNCs from fully aligned to core-shell architectures. These findings offer powerful quantitative guidelines for the digital manufacturing of composite materials with programmed particle orientations and properties.
Language
  • English
Open access status
closed
Identifiers
Persistent URL
https://sonar.ch/global/documents/66546
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