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

Abstract

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