This document summarizes research on designing and fabricating customized bone scaffolds for femur bones using 3D printing. The researchers used CT scan data of a femur bone in MIMICS software to create a 3D model. Four layers of the femur bone were selected to create customized scaffolds. Unit cell designs like double bend curves, S bend curves, U bend curves, and steps were created in SOLIDWORKS. Basic primitives like squares, hexagons, and octagons of different pore sizes and distances were used to design scaffold structures. 108 customized femur bone scaffolds were modeled and their porosities determined using MIMICS. Scaffolds with U bend curves and square primitives of 0.8mm pore

1. Design and Fabrication of Customised Scaffold for Femur Bone using
3D Printing
V.Iraimudi1,a
,S. Rashia Begum2,b
, G.Arumaikkannu1,c
and R.Narayanan1,d
1
Department of Manufacturing Engineering, Anna University, Chennai-25, Tamil Nadu, India.
2
Department of Mechanical Engineering, Anna University, Chennai-25, Tamil Nadu, India.
a
kanna.irai@gmail.com, b
rashia_ibrahim@yahoo.com,c
arumaik@gmail.com,
d
narayanan.rceg@gmail.com
Keywords: Additive Manufacturing (AM); Bone Scaffold; Pore size; Porosity; MIMICS.
Abstract. Additive Manufacturing is a promising field for making three dimensional scaffolds in
which parts are fabricated directly from the 3D CAD model. This paper presents, the patient’s CT
scan data of femur bone in DICOM format is exported into MIMICS software to stack 2D scan data
into 3D model. Four layers of femur bone were selected for creation of customised femur bone
scaffold. Unit cell designs such as double bend curve, S bend curve, U bend curve and steps were
designed using SOLIDWORKS software. Basic primitives namely square, hexagon and octagon
primitives of pore size 0.6mm, 0.7 mm and 0.8 mm diameter and inter distance 0.7mm, 0.8mm and
0.9 mm are used to design the scaffold structures. In 3matic software, patterns were developed by
using the above four unit cells. Then, the four layers of bone and patterns were imported into 3matic
to create customised bone scaffolds. The porosities of customised femur bone scaffold were
determined using the MIMICS software. It was found that the customised femur bone scaffolds for
the unit cell design of U bend curve with square primitives of pore size 0.8mm diameter and inter
distance 0.7mm gives higher porosity of 56.58 % compared to other scaffolds. The models were
then fabricated using 3D printing technique.
Introduction
Additive Manufacturing (AM) defined by ASTM [1], as the “process of joining materials to
make objects from 3D model data, usually layer upon layer, as opposed to subtractive
manufacturing methodologies, such as traditional machining”. The work involves the combination
of AM and Tissue Engineering(TE) concepts to produce customized bone scaffolds for bone
replacement. TE techniques generally require the use of a porous scaffold, which serves as a three
dimensional template for initial cell attachment and subsequent tissue formation both in vitro and in
vivo. The scaffold provides the necessary support for cells to attach, proliferate, and maintain their
differentiated function. Scaffolds fabricated using the traditional machining lack in pore strength,
interconnectivity and porosity. Additive Manufacturing (AM) techniques have been found to be
advantageous for TE scaffold fabrication due to their ability to address and overcome the problems
of uncontrollable architecture and the ability to manufacture complex 3D structures[2,3]. As the
scaffold's material properties and geometry plays a vital role in deciding its compatibility with the
tissues, a biocompatible material, medical grade MED 610, has been selected and fabricated using
3D printing. 3D printing is a process in which water-based liquid binder is supplied in a jet onto a
starch-based powder to print the data from a CAD drawing. The powder particles lie in a powder
bed and they are glued together when the binder is jetted. This process can handle a high variety of
polymers [4,5]. A high porosity and an adequate pore size are necessary to facilitate cell seeding
and diffusion throughout the whole structure of both cells and nutrients. The porosity of a scaffold
structure is directly related to its mechanical strength. Some of the issues need to be concentrated
prior to AM techniques are computer modelling of porous structures which control
interconnectivity, pore size and porosity. This paper presents, the design of customised femur bone
Advanced Materials Research Vol. 845 (2014) pp 920-924
Online available since 2013/Dec/04 at www.scientific.net
© (2014) Trans Tech Publications, Switzerland
doi:10.4028/www.scientific.net/AMR.845.920
All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP,
www.ttp.net. (ID: 14.139.161.3-21/11/14,08:07:56)

2. scaffolds with square, hexagon and octagon primitives of pore size 0.6mm, 0.7 mm and 0.8 mm
diameter and inter distance 0.7mm, 0.8mm and 0.9 mm with unit cell designs such as double bend
curve, S bend curve, U bend curve and steps using MIMICS software. The porosities of customised
femur bone scaffolds were determined using MIMICS software and the customised femur bone
scaffolds with U bend curve were fabricated using 3D printing technique with Bio-compatible
PolyJet photopolymer Medical Grade 610 material
Development of Customised Bone Scaffold
Modelling of the femur bone scaffold involves the use of CAD (Computer Aided Design)
techniques with AM methods to build customised TE scaffolds. The creation of 3-dimensional
porous scaffold architecture depends on commonly used medical imaging methodologies, especially
computed tomography (CT) and Magnetic Resonance Imaging (MRI). The CAD module of the
MIMICS software uses the femur bone in DICOM format obtained from CT scan and converts it
into a CAD model. The region of interest is isolated from the 3D model in MIMICS and then it is
intersected with the unit cell pattern using Boolean techniques resulting in the final scaffold.
Development of unit cell. Unit cell designs such as double bend curve, S bend curve, U bend
curve and steps were designed using SOLIDWORKS software and it is presented in Table 1.
Table 1. Unit cell designs
DOUBLE BEND
CURVE
U BEND CURVE S BEND CURVE STEP
Modeling of customised femur bone. The Computed Tomography (CT) scan data are used in
Materialise Interactive Medical Image Control System (MIMICS) software to get three dimensional
details of the Bone. The MIMICS, an image processing software package is used to convert the CT
data into a series of contours to simulate outer cortical and intramedullary cancellous surfaces by
segmentation and 3D rendering objects. The extracted cortical and trabacular bone features from
MIMICS is shown in Fig. 2. Then region growing is used to separate the Region Of Interest (ROI)
from the selected object. Four layers of femur bone are selected in MIMICS and are sliced from the
entire model and are shown in Fig.3. The total thickness of 4.62mm has been considered as
defective femur bone which is shown in Fig.4 and it is to be replaced by the customised bone
scaffold.
Development of customised bone scaffold using design patterns. Basic primitives namely
Square, Hexagon and Octagon primitives of pore size 0.6mm, 0.7 mm and 0.8 mm [6] and inter
distance of 0.7, 0.8 and 0.9 mm are used to design the scaffold structures. Unit cell designs such as
double bend curve, S bend curve, U bend curve and step were imported into 3 Matic module.
Fig.2. 3D Model of femur bone Fig.3. Region of Interest Fig.4. Four layers of femur bone
Advanced Materials Research Vol. 845 921

3. Steps in making porous scaffold structure. The Region of Interest (ROI) has 4 layers (3
slices). To enhance the scaffold strength a border clearance is left without developing pores in them.
For this the volume of the ROI is decreased by 10% and height is increased to 1.5 times which is
shown in Fig.5. The unit cell is imported into 3 Matic module in .stl format and intersected with the
scaled model and Boolean Intersection is performed which is shown in Fig.6. Then the original
scaffold model is imported and they intersect automatically as they have the same origin as shown
in Fig.7. Finally Boolean Subtraction is done to get the desired porous scaffold structure as shown
in Fig.8.
Fig.5. Scaled Model Fig.6. Assembled Unit Fig.7. Boolean Fig.8. Final Scaffold
Cell Pattern Operation
Totally 108 customised femur bone scaffolds were modeled using MIMICS software. The pore
analysis part of MIMICS software were used to determine the porosities of customised femur bone
scaffolds
Results and Discussions
Tissue Engineering scaffold characteristics and properties such as porosity, surface area to
volume ratio, pore size, pore interconnectivity, structural strength, shape (or overall geometry) and
biocompatibility are often considered to be critical factors in their design and fabrication[7].Thus a
total of 108 scaffold models were designed and initially 6 scaffold models were fabricated for
design verification. They were sectioned in a particular fashion so that the pore geometry is clearly
visible. The feasibility in fabricating the designed scaffold structures are verified by using the
sectioned scaffolds. The porosities of 108 scaffold models were determined using MIMICS
software. The porosity values and the design perfection achieved during the design verification
proved that scaffold with U-bend curves are better in terms porosity and good geometric replication
when converted into solid object on comparison with S-bend curves, double bend curves and Steps
unit cell designs. The porosities of scaffold structures designed using Step unit cell found to be low.
In case of Double Bend curves, the porosities were found anomalous. Comparing S-Bend Curve and
U-Bend Curve, pore geometry attained by the latter was found to be satisfactory. Therefore the
customised scaffolds with U-bend curves were decided for fabrication and its porosities alone were
presented. The relationship between porosity and inter distance for 27 scaffolds with U-bend curve
is shown in Fig.10. Hence 27 scaffolds (3 pore shapes, 3 pore sizes and 3 inter distances) were
fabricated by 3D printing using Bio-compatible PolyJet photopolymer Medical Grade 610 material
as shown in Fig.11.
922 Materials, Industrial, and Manufacturing Engineering Research Advances 1.1

4. Fig.10. Porosity (%) of scaffold structures using u-bend curve
Fig.10 Customised femur bone scaffold
Conclusion
This paper explores the possibility of using MIMICS software to convert DICOM images into
three dimensional scaffold model. The customised femur bone scaffolds with square, hexagon and
octagon primitives of pore size 0.6mm, 0.7 mm and 0.8 mm diameter and inter distance 0.7mm,
0.8mm and 0.9 mm with unit cell designs such as double bend curve, S bend curve, U bend curve
and steps were designed using MIMICS and 3 Matic software. The Porosities of 108 customised
bone scaffolds were determined using MIMICS software. It was found that the customised femur
bone scaffolds with U bend curve of square primitives of pore size 0.8mm diameter and inter
distance 0.7mm gives higher porosity of 56.58 % compared to other scaffolds. The 27 scaffolds (3
pore shapes, 3 pore sizes and 3 inter distances) were fabricated using 3D printing technique with
Bio-compatible PolyJet photopolymer Medical Grade 610 material.
Advanced Materials Research Vol. 845 923

5. References
[1] ASTM F2792-10.Standard Terminology for Additive Manufacturing Technologies,copyright
ASTM International,100 Barr Harbor Drive, West Conshohocken, PA 19428. www.astm.org.
[2] Chua CK, Leong KF, Cheah CM, Chua SW. Development of a tissue engineering scaffold
structure library for rapid prototyping. Part 1: investigation and classification. Int J Adv Manuf
Technol 2003;21:291–301
[3] Hutmacher DW, Sittinger M, Risbud MV. Scaffold-based tissue engineering: rationale for
computer-aided design and solid free-form fabrication systems.Trends Biotechnol
2004;22(7):354–62.
[4] J. W. Halloran, V. Tomeckova, S. Gentry et al., “Photopolymerization of powder suspensions
for shaping ceramics,” Journal of the European Ceramic Society, vol. 31, no. 14, pp. 2613–
2619, 2011
[5] Cooper, Rapid Prototyping Technology, Marcel Dekker, 2001.
[6] Chu TMG. Hollister SJ, Feinberg SE, 2001.Hydroxyapatite implants with design internal
architecture. Journal of Materials science: Materials in Medicine 12, 471-478.
[7] Yang S F, bong K F, Du Z H, Chua C K., 2001. The design of scaffolds for use in tissue
engineering. Tissue Engineering 7(6), 679-689.
924 Materials, Industrial, and Manufacturing Engineering Research Advances 1.1

6. Materials, Industrial, and Manufacturing Engineering Research Advances 1.1
10.4028/www.scientific.net/AMR.845
Design and Fabrication of Customised Scaffold for Femur Bone Using 3D Printing
10.4028/www.scientific.net/AMR.845.920