Direct-Write Deposition and Laser Processing of Dry Fine powders
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Direct-Write Deposition and Laser Processing of Dry Fine powders Pranav Kumar and Suman Das Mechanical Engineering Department, University of Michigan Ann Arbor, MI 48109-2125, U.S.A. ABSTRACT We present a concept for multi-material solid freeform fabrication of 2D and layered 3D heterogeneous components. This technique involves direct-write deposition of multiple, patterned powder materials followed by laser processing. The direct-write deposition system features miniature hopper-nozzles for depositing dry powdered materials by gravity or by high frequency vibration-assisted flow onto a movable substrate. A dual wavelength laser processing workstation was used to consolidate the deposited pattern to desired densities. The feasibility of this concept was proved by direct-writing and laser processing various powder material patterns. INTRODUCTION Solid Freeform Fabrication (SFF), also commonly known as rapid prototyping (RP) is a collective term for a group of technologies that can manufacture objects in a layer-by-layer fashion from the three-dimensional (3D) computer design of the object. Various SFF techniques have flourished over years and have been commercialized successfully. However, most of the SFF techniques presently available are for fabricating macroscale monolithic parts. In recent years, various researchers have attempted to develop new SFF and direct-write techniques for fabrication of meso- to microscale functional devices. Matrix assisted pulsed laser evaporation direct write (MAPLE-DW) is a new technique being developed for the rapid prototyping of electronic materials in order to fabricate mesoscale integrated electronic components [1]. In this technique powder material bound in an organic matrix is deposited using pulsed laser beam. MAPLE-DW has been used for depositing various patterned materials [1]. However, there is a considerable amount of pre-processing involved with this technique. Different materials require different matrices and each material/matrix system needs to be tailored separately for proper rheological properties. Other direct-write techniques under development such as robocasting [2], inkjet printing [3], hot-melt printing [4] and micropen writing [5] involve assembly via a layerby-layer deposition of colloidal based inks. These techniques have been used for a range of ceramic materials and offer powerful methods for producing 3D structures including microfluidic devices, tissue engineering scaffolds, and photonic band-gap structures. However, in these techniques as well, the colloidal ink for each material needs to be tailored in order to obtain well-controlled viscoelastic response, to ensure shape retention of deposited features, and to minimize drying-induced shrinkage. Thus, the pre-processing involved with these techniques can be tedious and time consuming. In the aforementioned techniques, post-processing involves removal of the organic solution or binder used to make the colloidal ink or the material/matrix by evaporation. Incomplete removal leaves a residue in t
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