Towards Realizing Melt-electrospun Bone Scaffolds: Theoretical Modeling and Simulation of Melt-Electrospinning as a Multi-body System
Creators: Wubneh, Abiy
Publisher: name: University of Alberta Library
Year: 2023

<p>There has been a growing interest in integrating melt-electrospinning (MES) with three-dimensional (3D) fabrication methods to produce constructs with controlled internal micro-architectures. One application area that could benefit from this integration is bone tissue engineering (TE). Due to the close functional and microarchitectural similarities between the melt-electrospun fiber depositions and the extracellular matrix (ECM) of the natural bone, melt-electrospun constructs have the potential to serve as ideal artificial environments for initial cell attachment and differentiation. The internal micro-structure of the construct, including the spatial distribution of accumulation densities and average fiber diameters, could be customized by controlling the processing parameters.</p>

<p>There are, however, significant technological gaps hindering the realization of this approach. Among them is the need for reliable methods for predicting the behavior of the process under a set of material and processing conditions. Available predictive models lack the necessary features to describe the process in its entirety, and their scope is usually limited to describing only a subset of the process. For example, while some models describe the jet initiation mechanism and Tailor’s cone formations, others focus only on characterizing the stable jet region. There are also existing models that describe the unstable region but are either based on oversimplified assumptions or do not consider some critical dynamical behaviors of the system affecting the fiber morphology.<br>
A theoretical predictive model is proposed in the present study to address these shortcomings. The proposed model aims to simulate the MES process under different material and processing conditions, including its potential use in simulating direct-writing and 3D printing scenarios. By treating the fiber as a serially-connected system, the fiber dynamics are formulated using Kane’s and Udwadia-Kalaba’s methods to take advantage of their suitability for multi-body systems with large numbers of components and complex constraints. The model formulation includes several advanced features, including Maxwell’s generalized standard linear solid (SLS) for improved viscoelastic behavior representation. The anchoring effects of the collector plate and independent motions of the spinneret and the collector plate are also included in the problem formulation to enable the simulation of direct-writing and 3D printing scenarios.</p>

<p>An experimental study is carried out to validate the model. The simulated results and the experimental observations are compared to assess the model’s predictive accuracy. The comparison revealed good agreement between the two, indicating the model’s reliability. In addition, as a byproduct of the investigation, two regression models are extracted from the observation data for predicting the collection and average fiber diameters, respectively. However, these regression models are limited to only stationary and vertical melt-spinning scenarios using polylactic acid (PLA) material.</p>

<p>A separate experimental investigation has been conducted to demonstrate the model’s capability in predicting direct-writing scenarios in which the melt-electrospun fibers are deposited based on predefined patterns. To test this new capability, the predictive model and an MES printer were run using the same toolpath (G-code) data and processing conditions. The results show reliable predictive accuracy, indicating that the model could be used for analyzing fiber behaviors.</p>

<p>Overall, this study presents a new theoretical predictive model for simulating the MES process, which has the potential to overcome the limitations of currently available tools. The model predicts with reasonable accuracy the deposition characteristics of melt-electrospun fibers under different material and processing conditions. It can also be used to simulate direct-writing scenarios. With further marginal improvement, the predictive model could accelerate the application of MES in 3D printing applications.</p>