Page 375 - IJB-10-5

International Journal of Bioprinting Tunable anisotropic gyroid bioscaffolds

Table 1. Summary of the geometric properties of the different sheet gyroid structures.
Model α β γ Value of Total surface area ϕ Designed porosity
2
C (x, y, z) (mm ) (%) (%)
40VF-gy 0.50 0.50 0.50 0.62 1602.8 40 60
50VF-gy 0.76 1567.3 50 50

60VF-gy 0.91 1512.5 60 40
57.55VF-gy 0.50 0.50 0.50 0.88 1525.2 57.55 42.45

γ.50-FGgy 0.50 0.50 0.50 C (x, y, z) 1551.9 57.55 42.45
γ.33-FGgy 0.33 1424.5 57.55 42.45
γ.25-FGgy 0.25 1363.8 57.55 42.45

development using isopropyl alcohol under ultrasonication a rate of 1.5°C/min to room temperature. Different dwell
for 30 min to remove excess slurry, followed by overnight times of 10, 20, 40, 80, 120, and 180 min were selected to
drying in a vacuum chamber at 60°C. compare the efficacy of the SMWH process (specimens
denoted as MW10m, MW20m, MW40m, MW80m,
2.3. Post-processing of the DLP-printed structures MW120m, MW180m) and conventional furnace heating
This study first employed a conventional furnace (specimens denoted as CS40m, CS80m, CS120m,
(Nabertherm HT29/17, Germany) and a commercial CS180m). The density, mechanical properties, and the
single-mode 2.45 GHz MW furnace (HAMiLab-HV3000, structural properties of the sintered specimens were
Synotherm, China) for the debinding and sintering process studied and compared.
of DLP 3D-printed specimens. A comparative study was
performed to assess the effectiveness of the SMWH process Subsequently, an innovative SHPS process was
for the post-processing of 3D-printed cube specimens. For employed using the MW furnace aimed at enhancing
SMWH process, a kiln with 2-mm-thick inner layer of the properties of the sintered specimens (Figure 3c). This
silicon carbide (SiC) was used as the susceptor for assisting involves the following stages:
the MW heating. The temperature profile of the debinding 1. In the first stage, the 3D-printed green specimens were
was defined by the TGA of the photo-cured SiO slurry, as heated to 600°C with a dwell time of 30 min under
2
shown in Figure 3a and b. From the TGA and derivative nitrogen (N ) atmosphere. Then, the specimens were
thermogravimetric (DTG) curves within the temperature cooled at a rate of 1.5°C/min to room temperature.
2
range of 50–800°C, weight loss started to occur at above During this stage, pyrolysis instead of debinding
325°C and a maximum weight loss was recorded at of the green specimens occurred, leaving residual
425.82°C. The weight loss rate reduced at around 525°C, carbon after the first heating stage and retaining the
signifying the decomposition of most organic matter. geometrical features of the 3D-printed specimens. 28
Within the test temperature, a maximum weight loss of
21.56% was recorded. 2. In the second stage, a two-step sintering process under
air atmosphere was employed, where the specimens
According to the TGA result, the debinding and were dwell at 800°C for 10 min to completely remove
sintering profile for the 3D-printed specimens was the residual carbon, followed by a dwell at 1150°C for
established. A fast-heating rate of 20°C/min was applied 120 min. The specimens were allowed to cool down at
throughout the study to exploit the merits of MW heating, a rate of 1.5°C/min to room temperature.
unless otherwise specified. The same heating profile,
involving a two-step heating as depicted in Figure 3b, was The quality of the specimens produced using the SHPS
used for both SMWH and conventional furnace heating process (specimens denoted as SHPS120m) was compared
process under air atmosphere. In brief, the specimens with those fabricated using conventional furnace, which
underwent a 30-min dwell time at 600°C for debinding, followed the manufacturer recommended heating profile
followed by sintering at 1150°C for a desired dwell time. with the same sintering dwell time of 120 min (specimens
Subsequently, the specimens were allowed to cool down at denoted as RCS120m), as shown in Figure 3d.

Volume 10 Issue 5 (2024) 367 doi: 10.36922/ijb.3609