InterLynk scientists from INEGI (M. Vila Pouca, N. Ramiao, M. Parente, RM Natal Jorge) and UAVR (J. Mano, R. Almeida) offer interesting insights in a recent publication "Simulating 3D printing on hydrogel inks: A finite element framework for predicting mechanical properties and scaffold deformation”. Published in "Finite Elements in Analysis and Design," in December 2023, this study delves into the challenges and solutions in 3D printing hydrogel scaffolds.

The research addresses a common issue in biofabrication: the distortion of 3D-printed scaffolds. These deformations, often overlooked, can significantly impact the scaffold's effectiveness in mimicking the target tissue's structure and properties. The team's approach involved developing a numerical framework using finite element analysis, a method that predicts deformations during the printing process. This framework is pivotal in defining optimal printing parameters, thereby reducing material waste and experimental efforts.

Key findings include the influence of printing speed on scaffold deformation. Intriguingly, scaffolds printed at a slower speed (5 mm/s) showed about 6% more deformation than those printed faster (10 mm/s). Despite these deformations, the overall mechanical properties of the scaffolds were similar, underscoring the complexity and nonlinear behavior of these biostructures.

The significance of this study lies in its potential to refine 3D printing techniques for hydrogel scaffolds, ensuring more accurate and reliable outcomes. By minimizing the experimental trial and error, this research marks a significant step forward in efficient and sustainable biofabrication practices.

As InterLynk continues to push the boundaries of medical science, stay tuned for more innovative research outcomes that promise to reshape the future of tissue regeneration and healing.

Reference

Title: Simulating 3D printing on hydrogel inks: A finite element framework for predicting mechanical properties and scaffold deformation

Journal: Finite Elements in Analysis and Design

Authors: M.C.P. Vila Pouca, M.R.G. Cerqueira, J.P.S. Ferreira, R. Darabi, N.A.G. Ramião, R. Sobreiro-Almeida, A.P.G. Castro, P.R. Fernandes, J.F. Mano, RM Natal Jorge, M.P.L. Parente

Date: Online version available since December 6, 2023

DOI: https://doi.org/10.1016/j.finel.2023.104098

Abstract:

Background: Difficulties during the wound healing process may result in scarring, chronic wounds and sepsis. A common tissue engineering strategy to solve these problems rely on the development of 3D hydrogel scaffolds that mimic the structure, stiffness, and biological proprieties of the target tissue. One of the most effective biofabrication techniques to precisely control spatial deposition, architecture and porosity of hydrogels is 3D printing technology. However, final architectures of 3D printed structures can be compromised if the printing properties are not adequately selected.

Purpose: Our main goal was to create a numerical framework able to predict the deformations that arise due to the 3D printing process of hydrogel scaffolds. Our secondary goal was to analyze if the overall mechanical properties of the 3D printed scaffolds were affected by these deformations.

Methods: We applied finite element analysis using ABAQUS finite element software to develop our numerical framework. The finite elements were added in a time sequence, simulating the material deposition. The bulk material was experimentally characterized and represented numerically by the user-defined subroutine UMAT. We tested the simulation by ‘printing’ a 5.0 × 5.0 × 0.8 alginate ink at 5 and 10 mm/s. Afterwards, both the final 3D printed scaffolds and a theoretical non-deformed configuration were subjected to a uniaxial compression of 10 % of the initial height, and differences between their overall mechanical properties were analyzed.

Results: The numerical framework captured the bending between the scaffold filaments and the compression of the bottom layers. On average, the scaffold printed at 5 mm/s deformed ∼6 % more, compared to the scaffold printed at 10 mm/s. However, in terms of overall mechanical properties, both showed similar behavior. This behavior, however, was highly nonlinear and significantly different from the theoretical, non-deformed scaffold, particularly in a small strains’ regime.

Conclusions: A numerical framework that can be used as a preliminary tool to define the printing velocity, sequence and geometry, minimizing the deformations during the 3D printing process was developed. This framework can help to minimize experimentation and consequently, material waste. We also saw that these deformations should not be neglected when predicting the mechanical behavior using finite element analysis, particularly for small strains application.