Page 391 - IJB-9-4

International Journal of Bioprinting

RESEARCH ARTICLE
Wall shear stress during impingement at the

building platform can exceed nozzle wall shear
stress in microvalve-based bioprinting

Ramin Nasehi, Sanja Aveic, Horst Fischer*

Department of Dental Materials and Biomaterials Research, RWTH Aachen University Hospital,
Aachen, Germany

Abstract

It is well known that in microvalve-based bioprinting, the cells are subjected to
wall shear stress, which can negatively affect their viability rate. We hypothesized
that the wall shear stress during impingement at the building platform, hitherto
not considered in microvalve-based bioprinting, can be even more critical for the
processed cells than the wall shear stress inside the nozzle. To test our hypothesis,
we used fluid mechanics numerical simulation based on finite volume method.
In addition, viability of two functionally different cell types, HaCaT cell line and
primary human umbilical vein endothelial cells (HUVECs), embedded in the cell-
laden hydrogel was assessed after bioprinting. Simulation results revealed that
at low upstream pressure the kinetic energy was not sufficient to overcome the
interfacial force for droplet formation and detachment. Oppositely, at relatively
mid upstream pressure, a droplet and a ligament were formed, whereas at higher
upstream pressure, a jet was formed between nozzle and platform. In the case of
*Corresponding author: jet formation, the shear stress during impingement can exceed the wall shear stress
Horst Fischer
(hfischer@ukaachen.de) in the nozzle. The amplitude of impingement shear stress depended on nozzle-to-
platform distance. This was confirmed by evaluating cell viability which revealed
Citation: Nasehi R, Aveic S, an increase of up to 10% when increasing the nozzle-to-platform distance from 0.3
Fischer H, 2023, Wall shear stress
during impingement at the building to 3 mm. In conclusion, the impingement-related shear stress can exceed the wall
platform can exceed nozzle wall shear stress in the nozzle in microvalve-based bioprinting. However, this critical issue
shear stress in microvalve-based can be successfully addressed by adapting the distance between the nozzle and
bioprinting. Int J Bioprint, 9(4): 743.
https://doi.org/10.18063/ijb.743 the building platform. Altogether, our results highlight impingement-related shear
stress as another essential parameter to consider in devising bioprinting strategies.
Received: January 19, 2023
Accepted: March 21, 2023
Published Online: May 3, 2023
Keywords: Bioprinting; Wall shear stress; Cell viability; Fluid mechanics; Numerical
Copyright: © 2023 Author(s). simulation
This is an Open Access article
distributed under the terms of the
Creative Commons Attribution
License, permitting distribution,
and reproduction in any medium, 1. Introduction
provided the original work is
properly cited. Several bioprinting methods have become established, including microextrusion ,
[1]
[3]
[2]
[7]
[4]
Publisher’s Note: Whioce inkjet , microvalve-based , vat polymerization-based , laser-based [5,6] , and acoustic
Publishing remains neutral with bioprinting. These methods vary in physical principle, printing resolution, and
regard to jurisdictional claims in [8,9]
published maps and institutional mechanical stimulation, all of which affect the processed cells . The choice of both
[10]
affiliations. bioink and method is usually made based on application . In the view of standardization
Volume 9 Issue 4 (2023) 383 https://doi.org/10.18063/ijb.743