John Vericella

Direct metal writing: Controlling the rheology through microstructure

Most metal additive manufacturing approaches are based on powder-bed melting techniques such as laser selective melting or electron beam melting, which often yield uncontrolled microstructures with defects (e.g., pores or microcracks) and residual stresses. Here, we introduce a proof-of-concept prototype of a 3D metal freeform fabrication process by direct writing of metallic alloys in the semi-solid regime. This process is achieved through controlling the particular microstructure and the rheological behavior of semi-solid alloy slurries, which demonstrate a well suited viscosity and a shear thinning property to retain the shape upon printing. The ability to control the microstructure through this method yields a flexible manufacturing route to fabricating 3D metal parts with full density and complex geometries.

Additive Micro-Manufacturing of Designer Materials

Material properties are governed by the chemical composition and spatial arrangement of constituent elements at multiple length scales. This fundamentally limits material properties with respect to each other creating trade-offs when selecting materials for a specific application. For example, strength and density are inherently linked so that, in general, the more dense the material, the stronger it is in bulk form. Other coupled material properties include thermal expansion and thermal conductivity, hardness and fracture toughness, strength and thermal expansion, etc. We are combining advanced microstructural design, using flexure and screw theory as well as topology optimization, with new additive micro- and nano-manufacturing techniques to create new material systems with previously unachievable property combinations. Our manufacturing techniques include Projection Microstereolithography (PμSL), Direct Ink Writing (DIW), and Electrophoretic Deposition (EPD). These processes are capable of reliably producing designed architectures that are highly three-dimensional, multi-scale, and often composed of multiple constituent materials.

Lightweight micro lattices with nanoscale features fabricated from Projection Microstereolithography

Complex, three-dimensional lightweight cellular materials inspired by nature, such as honeycomb and foamlike structures are desirable for a broad array of applications such as structural components, catalysts supports and energy efficient materials. Additionally, when designed with interconnected porosity, the open volume in the architecture can be exploited for active cooling or energy storage, providing unique opportunities for multifunctionality. However, they are extremely difficult to fabricate with the current state-of-the-art fabrication techniques. This paper reports the fabrication of complex, three-dimensional cellular materials with nanoscale features using a novel additive manufacturing approach, namely Projection Microstereolithography (PμSL).