Year: 2014
Type: dissertation
Abstract: RESUMELes progres faits en termes de microstructuration tridimensionnelle (3D) permettent la configuration d’architectures complexes, qu’elles soient faites de polymere seul ou renforce. Ces architectures peuvent participer a l'essor de nouvelles applications technologiques ou ameliorer des applications existantes.
Plusieurs strategies et technologies ont recemment emerge pour la fabrication rapide et peu couteuse de micro-appareils 3D faits a base de polymeres thermoplastiques. La deposition par fusion ou fused deposition est la methode la plus populaire pour la fabrication de produits 3D a base de thermoplastiques. Par contre, la degradation thermomecanique causee par les hautes temperatures du procede de deposition et par la haute viscosite de la plupart des polymeres fondus peut rendre difficile l'application de cette methode aux nanocomposites. En effet, les nanoparticules augmentent de facon significative la viscosite du materiau. Bien que le procede d'electro-filage ou ait ete utilise pour produire des structures polymetriques diverses, la complexite des structures 3D obtenues est relativement limitee. L'objectif general de cette these est le developpement d'une technique de fabrication permettant d'elaborer des structures 3D a base de materiaux nanocomposites constitues d'un polymere thermoplastique, le polylactide (PLA), et de nanotubes de carbone multi-parois.
Cette these presente le developpement d'une methode de fabrication par ecriture directe qui etend significativement les possibilites offertes par la microfabrication de structures 3D en nanocomposites thermoplastiques. Cette methode commence par la deposition robotisee d'un filament de polymere dissout dans un solvant par micro-extrusion. L'evaporation rapide du solvant permet la solidification directe du filament extrude. On peut donc donner a celui-ci des formes complexer en 3D comme par exemple des filaments, des tours, des echafaudages ou des spirales a forme libre. De plus, cette technique par evaporation de solvant a ete demontree comme etant abordable, hautement flexible et robuste pour la fabrication du microsystemes dont des fibres microstructurees a haute tenacite, des canaux microfluidiques ou des micro-antennes.----------ABSTRACT
Three-dimensional (3D) structures fabricated from polymers and their nanocomposites may find widespread technological applications which either require, or could benefit from, the ability to pattern micro-sized features in complex 3D architectures. Several strategies and technologies have recently emerged to rapidly and cost-effectively fabricate thermoplastic polymer-based 3D microdevices. Fused deposition modeling (FDM) stands out as the most popular procedure to manufacture 3D products. However, the thermal degradation caused by high processing temperatures and the high viscosity of most polymer melts may prevent the application of this technique to functional nanocomposite devices, since nanoparticles can significantly increase material viscosity. Also, electrospinning has been used to produce fiber-based polymer structures but is limited in terms of 3D structure complexity. The overall objective of this thesis is the development of a manufacturing technique allowing the fabrication of 3D structures of thermoplastic polymers and their nanocomposites.
This thesis reports the development of a direct-write fabrication technique that greatly extends the fabrication space for 3D thermoplastic nanocomposite structures. The solvent-cast 3D printing of microstructures uses a thermoplastic polymer or its nanocomposite solution as the ink. The method employs the robotically-controlled micro-extrusion of a filament combined with a rapid solvent evaporation. Upon drying, the increased rigidity of the extruded filament enables the creation of complex 3D shapes such as filaments, towers, scaffolds and freeform spirals. For a typical circular spiral, the average coil diameter was 966 ± 6 μm and the average pitch was 530 ± 25 μm. Both values were very close to the programmed deposition path (i.e., coil diameter of 1.0 mm, pitch of 500 μm). The layer-by-layer scaffold and the micro-cup were almost identical to their respective programmed deposition paths because the printing layer was supported by the underlying layer. The main limitation remains the freeform deposition of sharp turns which lead to some geometric discrepancies. Furthermore, the solvent-cast printing technique has been demonstrated to be a low-cost, highly flexible and powerful fabrication route of microsystems
Author: Shuang‐Zhuang Guo
Language: English
Subfield: Industrial and Manufacturing Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W1871339829