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Chow, et al.
A B C

Figure 3. Differences between the suggested hypertrophic scars (HS) treatment with customized silicone
insert and traditional silicone gel sheet therapy: (A) Photograph of the HS; (B) Demonstration of tropical
silicone gel sheet therapy; (C) Demonstration of suggested HS treatment with customized silicone insert.

and textiles . The schematic diagram of ASTM
[34]
D5169 is shown in Figure 5D. Images of the
3D printing process of ASTM D5169 samples
for mechanical characterization and the printed
sample are shown in Figure 5E and F.
The maximum shearing force of the 0.2 wt%_
Figure 4. Schematic of multi-material approach Thickener _0.4 mm elevated sample is around 60
on elevated fabric. N which is a 600% improvement in comparison
to the result of 2 wt%_Thickener sample;
reference shown in Figure 5A for various materials Figure 5G and H. When comparing the 0.2
printing on fabric. Theoretically, lower viscosity of wt%_Thickener _0.4 mm and 0.2 wt%_Thickener
print mixture is easier to diffuse through the fabric. samples, the elevation of fabric increases around
However, too low viscosity print mixture may 50% of maximum shearing force. To investigate
cause the undesirable diffusion and migration of the surface morphology of the samples, blue and
the silicone mixture, adversely affecting the control red pigments were added to the print mixtures of
of the printing process and the ultimate size and the first and other layers, respectively. It is shown
shape of the printed composite. Figure 5B and C in Figure 5Ii and Iii that more of the silicone
shows the problem of extremely low viscosity print mixture has diffused through the fabric in 0.2
mixture during printing. The first layer of printed wt%_Thickener_0.4 mm sample when compared
silicone mixture in Figure 5B without thickener to 0.2 wt%_Thickener sample which demonstrates
which spread along the print platform before curing the effect of the elevating the layer of fabric. For
and causing improper size of printed material. the 0.2 wt%_Thickener_0.4 mm elevated sample,
Therefore, 0.2 wt% thickener was added to increase due to the elevation of fabric, extra capacity is
the viscosity of mixture from around 2300 to 7400 provided for the diffusion of the silicone mixture.
Mpa·s for the first layer of printing (Figure 5C). To As a result, a sandwich structure composite was
further improve the adhesion between the fabric and fabricated, which consists of two silicone outer
silicone, a metal plate was placed between the fabric skins and a fabric core structure. The sandwich
and the build platform that the fabric specimen was structure of sample increases the contact surface
elevated to accommodate the deposition of silicone area between the silicone and fabric and, at the same
mixture. At the same time, the temperature of the time, creates mechanical barriers that interlock the
build platform was set to 70ºC to facilitate the porous fabric. Consequently, the adhesive force of
curing of the 3D printed silicone to create a stable this sample is significantly higher since tearing of
base for the above layers. silicone is required to separate the silicone from
The adhesion force of the samples was the fabric. In contrast, the silicone mixture with
determined using ASTM D5169, which is used high viscosity 2 wt%_Thickener sample did not
to examine the adhesion of 3D printed materials diffuse through the fabric or absorbed by the yarn,

International Journal of Bioprinting (2020)–Volume 6, Issue 2 75