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Daskalakis, et al.
by Perstorp Caprolactones (Cheshire, UK) in the form of was used to create a continuous path planning algorithm,
pellets. Hydroxyapatite (HA) (Mw = 502.31 r/mol, MP using zig-zag (25 and 38 double filaments) and spiral-
= 1100 C) was supplied by Sigma-Aldrich (St. Louis, like patterns (6 and 14 filaments) to produce four groups
o
USA) in a nanopowder form (<200 mm particles size) of bone bricks with overall porosity varying between
and β-tri-calcium phosphate (TCP) (Mw = 310.18 r/mol, 52% and 74% (Figure 2). The process parameters
MP = 1391°C) was supplied by Sigma-Aldrich (St. Louis, used for the production of the bone bricks were
USA) in a nanopowder form (<200 mm particles size). melting temperature 90°C, deposition velocity of 18
PCL composite blends containing different bioceramics mm/s, and screw rotation velocity of 14 rpm. During the
contents (20 wt% HA, 20 wt% TCP, and 10 wt% HA production process, the composite pellets were placed
plus 10 wt% TCP) were produced by melt blending. PCL in a heated reservoir, melted, and moved to the screw
pellets were measured using an electronic weighting chamber using compressed air and extruded out with the
high precision balance (precision of 0.0001) and melted use of a needle. The composite leaves the extruder in a
at 150°C in a porcelain bowl before adding the ceramic molten state, cooling down in the working platform. The
material. Composite materials were mixed around 1 diameter of the needle was 0.33 mm.
h to ensure a uniform distribution of the ceramics in
the polymer matrix and cut down in small pellets after 2.3. Morphological characterization
cooling.
The morphology of printed bone bricks was investigated
2.2. Production using the scanning electron microscopy (SEM) FEI
ESEM Quanta 200 (FEI Company, United States) at an
Bone bricks were produced using the material accelerated voltage of 15 kV. EMITECH K550X sputter
extrusion additive manufacturing 3D Discovery coater (Quorum Technologies, UK) was used for coating
system (RegenHU, Switzerland). A computational the structures (gold coating) prior imaging. The obtained
geometry-based algorithm, with data collected from images were processed by ImageJ (NIH, USA), allowing
anthropometric measurements by surgeons in Turkey, to determine the PS, the filament width (FW), and the

Figure 2. Anthropometric based geometries and different path planning strategies considered to produce bone bricks with different porosities.
International Journal of Bioprinting (2021)–Volume 7, Issue 2 45