Continuous Liquid Interface Production (CLIP) for the Fabrication of Porous Architected Structures

Porous structures have long been investigated for advanced material properties however conventional fabrication methods do not have the necessary specificity to dictate void volume size, shape and distribution. Additive manufacturing (AM), or more commonly 3D printing, is a rapidly growing field in which material is selectively deposited in a layer wise manner as instructed by a computer-aided design (CAD). Therefore, AM has been seen as an attractive route for fabrication of porous structures. While many AM platforms have been investigated, the overall disadvantage with these processes has been the layer wise assembly method, which yields mechanically weak parts. Additionally, many methods impart an unintentional porosity on the resulting structure that deviates from CAD and aids in the mechanical failure mechanisms. This work sought to investigate and apply a novel AM platform, continuous liquid interface production (CLIP), to the fabrication of porous architected structures. The platform utilizes photopolymerization to reconstruct the CAD in a continuous manner. The platform was investigated for porous structure compatibility through assessment of the fabrication mechanism. It was found that CLIP structures fabricated continuously were layerless, addressing one of the key disadvantages with other platforms. The resolution of CLIP was preliminaryily explored and several contributing factors were identified. The resolution of the CLIP platform was investigated for the fabrication of porous architected structures. Void volumes in the hundreds of microns regime was explored through the fabrication of microlattices. Structures were systematically varied by unit cell type, size, orientation, resin formulation, and CLIP fabrication parameters. The resulting mechanical and physical property space was investigated. The lessons of the importance of low viscosity resin and exposure were carried forward. The tens of micron size range was explored through the fabrication of chromatography columns containg ordered internal architectures with CLIP. Functional resins to enable different separation mechanisms were developed and optimized for CLIP. The pore size of the internal architecture of the column was systematically reduced. The computational limit for CAD generation of complex structures was found and an angular hexagonally packed unit cell designed to facilitate computation as well as mimic monolithic column flow profiles was developed. Columns assembled with CLIP fabricated external housings were assessed for stability. Methods to circumvent computational constraints were developed to allow direct exposure of the light source which enabled the fabrication of smaller pore sizes approaching the theoretical limit of resolution.Doctor of Philosoph

Layerless fabrication with continuous liquid interface production

Despite the increasing popularity of 3D printing, also known as additive manufacturing (AM), the technique has not developed beyond the realm of rapid prototyping. This confinement of the field can be attributed to the inherent flaws of layer-by-layer printing and, in particular, anisotropic mechanical properties that depend on print direction, visible by the staircasing surface finish effect. Continuous liquid interface production (CLIP) is an alternative approach to AM that capitalizes on the fundamental principle of oxygen-inhibited photopolymerization to generate a continual liquid interface of uncured resin between the growing part and the exposure window. This interface eliminates the necessity of an iterative layer-by-layer process, allowing for continuous production. Herein we report the advantages of continuous production, specifically the fabrication of layerless parts. These advantages enable the fabrication of large overhangs without the use of supports, reduction of the staircasing effect without compromising fabrication time, and isotropic mechanical properties. Combined, these advantages result in multiple indicators of layerless and monolithic fabrication using CLIP technology

Layerless fabrication with continuous liquid interface production

Despite the increasing popularity of 3D printing, also known as additive manufacturing (AM), the technique has not developed beyond the realm of rapid prototyping. This confinement of the field can be attributed to the inherent flaws of layer-by-layer printing and, in particular, anisotropic mechanical properties that depend on print direction, visible by the staircasing surface finish effect. Continuous liquid interface production (CLIP) is an alternative approach to AM that capitalizes on the fundamental principle of oxygen-inhibited photopolymerization to generate a continual liquid interface of uncured resin between the growing part and the exposure window. This interface eliminates the necessity of an iterative layer-by-layer process, allowing for continuous production. Herein we report the advantages of continuous production, specifically the fabrication of layerless parts. These advantages enable the fabrication of large overhangs without the use of supports, reduction of the staircasing effect without compromising fabrication time, and isotropic mechanical properties. Combined, these advantages result in multiple indicators of layerless and monolithic fabrication using CLIP technology

Liquid perfluoropolyether electrolytes with enhanced ionic conductivity for lithium battery applications

We prepared nonflammable liquid polymer electrolytes for lithium-ion batteries by mixing ethoxylated perfluoropolyethers (PFPEs) with LiN(SO2CF3)2 salt. Interestingly, we identified the presence of chain coupling in the PFPE polymers and their functionalized derivatives, resulting in a mixture of PFPEs with varying molecular weights. The distribution of molecular weights, along with PFPE's multiple functionalities, allows systematic manipulation of structure to enhance electrochemical and physical properties. Furthermore, the electrolytes exhibited a wide thermal stability window (5% degradation temperature >180 °C). Despite substantial increases in viscosity upon loading the PFPEs with lithium salt, the conductivity (σ ≈ 5 × 10−5 S cm−1 at 28 °C) of the novel electrolytes was about an order of magnitude higher than that of our previously reported PFPE electrolytes. Ethoxylated derivatives of PFPE electrolytes exhibit elevated conductivity compared to non-ethoxylated derivatives, demonstrating our capability to enhance the conductive properties of the PFPE platform by attaching various functional groups to the polymer backbone