ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

DESIGN AND STRUCTURAL EVALUATION OF SCAFFOLDS
PROTOTYPES OBTAINED BY SELECTIVE LASER SINTERING
P. Coelho 1 , C. Flanagan 2 , S. Hollister 3 , P. Fernandes 4 and H. Rodrigues 5
1. ABSTRACT
In this work three scaffold microstructures for lumbar spine are designed via multiscale
topology optimization. An animal model of a Yucatan minipig is used for the modeling
of the lumbar spine. The scaffold design is carried out balancing mechanical and masstransport
properties. Scaffolds prototypes are manufactured by Selective Laser Sintering
and subjected to compressive mechanical testing for validation purposes.
2. INTRODUCTION
The design of scaffolds for bone tissue engineering with controlled microstructure has
been an area of interest since it permits to obtain scaffolds with properties that satisfy
mechanical and biological requirements [1,2]. Design methodologies imply to solve
optimization problems in the continuum mechanics context that return optimal material
microstructures with equivalent macroscopic elastic properties usually obtained by
homogenization techniques. As regards the fabrication of scaffolds with controlled
microstructure Rapid Prototyping (RP) techniques are particularly adequate, e.g.
Selective Laser Sintering (SLS). The process of converting data from finite elements
codes to STL files may involve some perturbation of geometrical features. Furthermore,
the final product and its experimental testing may differ from predicted numerical
simulations. This motivates research work in order to evaluate mechanical properties
and then conciliate experimental and numerical results. In this work the actual
properties of scaffolds are assessed, both experimentally and using the Finite Element
(FE) Method. Three scaffold microstructures are designed via multiscale topology
optimization balancing mechanical and mass-transport properties [3,4]. Then, SLS is
used to fabricate prototypes in Polycaprolactone (PCL) with 4% Hydroxyapatite. The
specimens manufactured correspond to periodic patterns of 4×4×8 unit-cells. Different
sizes of specimens are built varying the length of the unit-cell edge (2, 3 or 4 mm). The
Young Modulus along x, y and z directions are evaluated by compressive testing. Each
experimental testing is simulated numerically running a FE linear analysis. The results
show a correlation between numerical and experimental compressive testing data, for all
designs, sizes and directions.
1
Professor, Department of Mechanical and Industrial Engineering, The New University of Lisbon, 2829-
516 Caparica, Portugal
2
Biomedical Engineer, Department of Biomedical Engineering , University of Michigan, Michigan
48109-2125, USA.
3
Professor, Department of Biomedical Engineering , University of Michigan, Michigan 48109-2125,
USA.
4
Professor, IDMEC, Technical University of Lisbon, Av. Rovisco Pais 1, 1049-001 Lisboa, Portugal.
5
Professor, IDMEC, Technical University of Lisbon, Av. Rovisco Pais 1, 1049-001 Lisboa, Portugal.