Polycaprolactone-based Scaffolds Fabricated Using Fused Deposition Modelling or Melt Extrusion Techniques for Bone Tissue Engineering - Biointerfaces: Where Material Meets Biology - page 227

Table 9.2 Processing parameters using FDM and ME with their respective

effects. 13,14

FDM (spool) ME (chamber) Effects

Roller speed Air pressure

and rotating
screw speed

Determines the material feed rate into the
liquefier (FDM)/extrusion chamber (ME) and the
molten material out of the nozzle. Changes in
roller speed/air pressure/rotating screw speed
will affect the flow rate of molten material out of
the nozzle and the road width (RW) of the laid
microfilament.

d n 3 r 4 n g | 1

Liquefier
temperature

Temperature
of the
heating coils

Changes in temperature affect the viscosity of the
material. Raising the temperature beyond the
material melting temperature can reduce
material viscosity. Excess temperature may
damage the material, or induce degradation of
molecular weight over time.

Speed of the
extrusion head

Speed of the
collecting
platform

Determines the output of machine. Increased
extrusion had/collecting platform
speed ¼ increased machine output.

Direction of deposition Determines the lay-down pattern/raster angle (RA)

of scaffold.

Nozzle size Determines the diameter/RW of the extruded

microfilament.

Nozzle translational speed Ensures consistent and uniform extrusion of the

microfilament. Can be regulated to allow for
stretching of the microfilament. This parameter
works in conjunction with the flow rate.

Fill gap (FG) Determines the distance between laid

microfilaments. This parameter determines the
stability and porosity of the engineered
construct.

.

Flow rate Defined as the speed of extrusion of molten

material. Determined by the viscosity of molten
material, roller speed

9.3 Polycapralactone Scaffolds

9.3.1 Physical Characteristics of Polycaprolactone Scaffolds
The requirements of a scaffold for bone TE are very demanding. As well as
meeting the requirements of a 3D scaffold to support cell attachment and
survival, these scaffolds also need to provide suitable mechanical support
post-implantation and throughout the duration of healing. A number of
candidate polymers possess suitable properties and this chapter will focus
on PCL and composites thereof. A number of structures have been explored
using PCL for bone tissue engineering and several are detailed in Figure 9.2.
The recent resurgence of PCL research has coincided with the tissue en-
gineering AM revolution. Initial studies focused on two main areas: (1) the
porosity/strength compromise of FDM/ME PCL scaffolds, and (2) in vivo and
in vitro biocompatibility of these scaffolds.