I-Corps: Micro-scale computed axial lithography for 3D fabrication in challenging materials

University Of California-Berkeley, Berkeley CA

Investigators

Abstract

The broader impact/commercial potential of this I-Corps project is the development of a microscale computed axial lithography additive manufacturing process. Inorganic materials including glasses and ceramics have high temperature and chemical resistance, high stiffness and strength, and biological inertness. Due to the brittleness of the raw material, manufacturing of complex geometries is challenging and, historically, has been dominated by subtractive machining operations including milling, grinding, and chemical etching. However, as technological advances motivate the manufacture of customized application-specific devices with unique 3D morphologies, the conventional fabrication methods are inherently limited by material removal unit processes. The proposed technology is designed for rapid production of 3D microstructures with relatively smooth surfaces. This may be used in the manufacture of microfluidic devices (including micromixers) with high optical clarity, inertness, and suitability for challenging chemical environments. In addition, the proposed technology may achieve customized geometries with multiple fluidic channel depths in low-volume production. This level of customization is not easily achievable with conventional short-run fabrication methods such as wet chemical etching, or injection molding. For example, the technology may be used to enable the rapid and precise printing of customized dental crowns, where each crown must be unique and tailored to fit the shape of the patient’s teeth. The proposed technology also may be applied to producing mold inserts for injection molding processes. In the future, this technology may reduce manufacturing costs and enable the customization of high-precision parts for a wide range of industries including dental, medical, and semiconductor. This I-Corps project is based on the development of an additive manufacturing technology called computed axial lithography (CAL). The proposed technology is a volumetric, light-based, micro-scale photopolymerization method conceptually analogous to the inverse of computed tomography. Parts are printed by exposing a container of photoresponsive material to computed light patterns from many angles and the integrated light dose photopolymerizes a prescribed 3D geometry. The process is currently capable of defining geometries with 50 µm positive feature size and 150 µm internal channel diameters in silica glass nanocomposite materials within a few seconds. After thermal post-processing, complex solid silica glass geometries with high optical transparency and nanometer-level surface roughness may be achieved. In addition, the process by be used for printing directly into organic photopolymer resins, and processes for other ceramic nanocomposites with specialized applications are under development. The merits of this technique over industrially established layer-by-layer methods include its higher throughput, lower surface roughness, and elimination of wasteful solid print-supporting structures. The lower surface roughness makes the process potentially attractive for applications where aesthetic clarity is important, and for producing custom micro-optical components. Fracture testing results indicate that the lower roughness results in a tighter distribution of mechanical strength in micro-CAL-printed components than in layer-by-layer-printed parts. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.