431 Next Generation Biomedical Implants Using Additive Manufacturing of Complex, Cellular and Functional Mesh Arrays

Friday, November 6, 2009: 9:00 AM
Pancho Villa (Camino Real Hotel)
Lawrence E. Murr, Ph.D. , Metallurgical and Materials Engineering, University of Texas at El Paso, El Paso, TX
L. E. Murr1,2*, S. M. Gaytan1,2, F. Medina,2, H. Lopez1, E. Martinez1,2, B. I. Machado1.2, D. H. Hernandez1,2, L. Martinez1,2, M. I. Lopez1,2, R. B. Wicker2,3, J. Bracke4

1Department of Metallurgical and Materials Engineering, The University of Texas at El Paso, El Paso, TX 79968 USA, 2W. M. Keck Center for 3D Innovation, The University of Texas at El Paso, El Paso, TX 79968 USA, 3Department of Mechanical Engineering, The University of Texas at El Paso, El Paso, TX 79968 USA 4Integrated Material Control Engineering,
n.v., Genk, Belgium

Abstract

In this paper we examine prospects for the manufacture of patient-specific biomedical implants replacing hard tissues (bone), particularly knee and hip stems and large bone (femoral) intramedullary rods using additive manufacturing (AM) by electron beam melting (EBM).  Of particular interest is the fabrication of complex functional (biocompatible) mesh arrays.  Mesh elements or unit cells can be divided into different regions in order to use different cell designs in different areas of the component to produce various or continually varying (functionally graded) mesh densities.  Numerous design elements have been used to fabricate prototypes by ALM using EBM of Ti-6Al-4V powders where the densities have been compared with elastic (Young’s) moduli determined by resonant frequency and damping analysis.  Density optimization at the bone-implant interface can allow for bone ingrowth and cementless implant components.  Computerized tomography (CT) scans of metal (aluminum alloy) foam has also allowed for the building of Ti-6Al-4V foams by embedding the digital-layered scans in CAD or software models for EBM.  Variations in mesh complexity and especially strut (or truss) dimensions alter the cooling and solidification rate, which alters the α-phase (hcp) microstructure by creating mixtures of α/α̕ (martensite) observed by optical and electron metallography.  Microindentation hardness measurements are characteristic of these microstructures and microstructure mixtures (α/α') and sizes.

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