Daniel Therriault

Three-Dimensional Printing of Multifunctional Nanocomposites: Manufacturing Techniques and Applications.

The integration of nanotechnology into three-dimensional printing (3DP) offers huge potential and opportunities for the manufacturing of 3D engineered materials exhibiting optimized properties and multifunctionality. The literature relating to different 3DP techniques used to fabricate 3D structures at the macro- and microscale made of nanocomposite materials is reviewed here. The current state-of-the-art fabrication methods, their main characteristics (e.g., resolutions, advantages, limitations), the process parameters, and materials requirements are discussed. A comprehensive review is carried out on the use of metal- and carbon-based nanomaterials incorporated into polymers or hydrogels for the manufacturing of 3D structures, mostly at the microscale, using different 3D-printing techniques. Several methods, including but not limited to micro-stereolithography, extrusion-based direct-write technologies, inkjet-printing techniques, and popular powder-bed technology, are discussed. Various examples of 3D nanocomposite macro- and microstructures manufactured using different 3D-printing technologies for a wide range of domains such as microelectromechanical systems (MEMS), lab-on-a-chip, microfluidics, engineered materials and composites, microelectronics, tissue engineering, and biosystems are reviewed. Parallel advances on materials and techniques are still required in order to employ the full potential of 3D printing of multifunctional nanocomposites.

Ultraviolet‐Assisted Direct‐Write Fabrication of Carbon Nanotube/Polymer Nanocomposite Microcoils

[*] Prof. D. Therriault, L. L. Lebel Laboratory of Multi-scale Mechanics, Center for Applied Research on Polymers (CREPEC) École Polytechnique of Montreal C.P. 6079, succ. Centre-Ville, Montreal, QC H3C 3A7 (Canada) E-mail: daniel.therriault@polymtl.ca B. Aissa, Prof. M. A. E. Khakani Institut National de la Recherche Scientifique, INRS-Énergie, Matériaux et Télécommunications 1650 Blvd. Lionel-Boulet, Varennes, QC J3X 1S2 (Canada)

Solvent‐Cast Three‐Dimensional Printing of Multifunctional Microsystems

The solvent-cast direct-write fabrication of microstructures is shown using a thermoplastic polymer solution ink. The method employs the robotically controlled microextrusion of a filament combined with a rapid solvent evaporation. Upon drying, the increased rigidity of the extruded filament enables the creation of complex freeform 3D shapes.

Self-Healing Materials Systems: Overview of Major Approaches and Recent Developed Technologies

The development of self-healing materials is now being considered for real engineering applications. Over the past few decades, there has been a huge interest in materials that can self-heal, as this property can increase materials lifetime, reduce replacement costs, and improve product safety. Self-healing systems can be made from a variety of polymers and metallic materials. This paper reviews the main technologies currently being developed, particularly on the thermosetting composite polymeric systems. An overview of various self-healing concepts over the past decade is then presented. Finally, a perspective on future self-healing approaches using this biomimetic technique is offered. The intention is to stimulate debate and reinforce the importance of a multidisciplinary approach in this exciting field.

Properties of polylactide inks for solvent-cast printing of three-dimensional freeform microstructures.

Solvent-cast printing is a highly versatile microfabrication technique that can be used to construct various geometries such as filaments, towers, scaffolds, and freeform circular spirals by the robotic deposition of a polymer solution ink onto a moving stage. In this work, we have performed a comprehensive characterization of the solvent-cast printing process using polylactide (PLA) solutions by analyzing the flow behavior of the solutions, the solvent evaporation kinetics, and the effect of process-related parameters on the crystallization of the extruded filaments. Rotational rheometry at low to moderate shear rates showed a nearly Newtonian behavior of the PLA solutions, while capillary flow analysis based on process-related data indicated shear thinning at high shear rates. Solvent vaporization tests suggested that the internal diffusion of the solvent through the filaments controlled the solvent removal of the extrudates. Different kinds of three-dimensional (3D) structures including a layer-by-layer tower, nine-layer scaffold, and freeform spiral were fabricated, and a processing map was given to show the proper ranges of process-related parameters (i.e., polymer content, applied pressure, nozzle diameter, and robot velocity) for the different geometries. The results of differential scanning calorimetry revealed that slow solvent evaporation could increase the ability of PLA to complete its crystallization process during the filament drying stage. The method developed here offers a new perspective for manufacturing complex structures from polymer solutions and provides guidelines to optimize the various parameters for 3D geometry fabrication.

Preparation of Highly Exfoliated Polyester–Clay Nanocomposites: Process–Property Correlations

A large number of polyester nanocomposite batches featuring different kinds of nanoclay surface modifiers and up to 6 wt % nanoclay were manufactured using a solvent-based technique. Montmorillonite platelets modified with ammonium ions of different chemical architectures were examined to study the effect of ammonium ions on the extent of surface reactions with long-chain fatty acids. The ammonium montmorillonite was first dispersed and suspended in acetone. This suspension was further esterificated with dotriacontanoic (lacceroic) acid to form high density brushes on the clay surface. This led to achieving higher basal plane spacing of the montmorillonite platelets due to the reduction of electrostatic interactions holding them. The outcome of the surface esterification was analyzed by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The esterificated ammonium-modified clays were then mixed by five different mixing strategies based on the use of a three-roll mill mixer (TRM) and/or ultrasonication (US) to obtain the desired polyester-nanoclay dispersion, intercalation, and exfoliation. The dispersion states of the modified nanoclay in polymer were characterized from XRD, scanning electron microscopy (SEM), and low and high magnification transmission electron microscopy (TEM). Mechanical, thermal, and barrier properties of the resulting composites were experimentally characterized. The Mori-Tanaka method along with an orientation distribution function was used to verify the experimental effective stiffness of the polyester nanocomposite systems. The aspect ratio of nanoclays and their level of intercalation and/or exfoliation after mixing were also confirmed by the comparison of the experimental diffusivity results with those of Ficks diffusion model. Systems having 4 and 6 wt % esterificated ammonium nanoclay and prepared according to a combined TRM/US mixing procedure showed optimal performance with balanced properties and processing ease, thereby showing potential for use in the automotive, transportation, and packaging industries.

Micro-extrusion of organic inks for direct-write assembly

Direct-write assembly is a highly versatile microfabrication technique used to create microfluidic networks by the robotic deposition of a fugitive ink onto a moving stage. To optimize the resulting shape of the microchannel, the translational speed of the moving stage has to closely match the linear velocity of the fugitive ink at the micro-nozzle exit. In this work, we have performed a comprehensive characterization of the micro-extrusion process of organic fugitive inks through a nozzle and characterized the rheological properties of petroleum jelly-based organic inks with various microcrystalline wax contents (10 to 40 wt%). The local microcrystal concentration has been probed using polarized optical microscopy and Raman spectroscopy. Small amplitude oscillatory shear tests in a vane geometry have revealed a solid-like structure of the organic inks, and a strong shear-thinning behavior of the complex viscosity. Particle tracking velocimetry (PTV) experiments performed in a glass microchannel have suggested the occurrence of apparent slip, showing a microcrystal depletion layer near the nozzle wall and a plug flow in the remainder of the micro-nozzle. From Raman spectroscopy and polarized microscopy performed on extruded samples, a crystal free layer was observed and estimated to be approximately 10–20 µm thick (or 2–4% of the microcapillary diameter), explaining the strong apparent wall slip behavior.

A Microfluidic Packaging Technique for Lab-on-Chip Applications

In this paper, we address the often-neglected challenges of microfluidic packaging for biochemical sensors by proposing an efficient direct-write microfluidic packaging procedure. This low-cost procedure is performed through a programmable dispensing system right after a routine electronic packaging process. In order to prove the concept, the simulation, fabrication and chemical testing results of implemented hybrid system incorporating microelectronics and microfluidics are also presented and discussed.

PCB-Integrated Heat Exchanger for Cooling Electronics Using Microchannels Fabricated With the Direct-Write Method

The electronic industry has a growing need for efficient heat dissipation mechanisms such as micro heat exchanger systems. This active cooling approach requires the integration of microfluidic components near the main heat sources of the electronic devices. Despite the investigation of several micro-cooling configurations, their commercial utilization by the electronic industry is rather limited due to complex fabrication and integration methods. Here, we present the integration of cylindrical microchannels fabricated by direct-write assembly in printed circuit board layouts for a micro heat exchanger application. The thermal performance of the manufactured prototype was characterized with respect to the fluid flow rate. The original fabrication and integration approaches presented here show high potential for efficient, compact, and low-cost micro heat exchangers for the electronic industry.

Fluidic patch antenna based on liquid metal alloy/single-wall carbon-nanotubes operating at the S-band frequency

This letter describes the fabrication and characterization of a fluidic patch antenna operating at the S-band frequency (4 GHz). The antenna prototype is composed of a nanocomposite material made by a liquid metal alloy (eutectic gallium indium) blended with single-wall carbon-nanotube (SWNTs). The nanocomposite is then enclosed in a polymeric substrate by employing the UV-assisted direct-writing technology. The fluidic antennas specimens feature excellent performances, in perfect agreement with simulations, showing an increase in the electrical conductivity and reflection coefficient with respect to the SWNTs concentration. The effect of the SWNTs on the long-term stability of antennas mechanical properties is also demonstrated.