Page 528 - IJB-10-4

International Journal of Bioprinting 3D printed substrate for adhesion tests

2.7. Probe tack test groups, followed by Tukey’s multiple comparison test.
A t-test analysis was used to compare the two groups.
2.7.1. Pressure-sensitive adhesive The mean differences were considered significant in all
All PSAs were evaluated for their adhesion properties with experiments, valued at *p < 0.05, **p < 0.01, ***p < 0.001,
a probe tack test using a texture analyzer (TA.XTPlus; and ****p < 0.0001.
Stable Microsystems, Texture Technologies Corp, USA).
All PSAs were tested using industrial standard TA-57R SS 3. Results
probes and 3D-printed PP probes. The instrument was
first calibrated for force and distance. Patches were then 3.1. 3D printing of polypropylene probes, their
analyzed using: pre-test speed: 0.5 mm/s; test speed: 0.5 surface profile, and surface energy measurements
mm/s; post-test speed: 1 mm/s; applied force: 0.005 N; Our results demonstrated significant warping at parameter
return distance: 10 mm; contact time: 10 s; and trigger sets: 60°C chamber with a 0°C build platform; 100°C
force: 0.003 N. Force versus Distance graphs were then chamber with a 0°C build platform; and 80°C for both the
30
obtained and used for calculating the peak adhesive force chamber and build platform. These conditions resulted
(Figure S3a, Supporting Information). in unacceptable probe geometries, rendering the printed
probes unfit for subsequent testing (Figure S2a, Supporting
2.7.2. Human skin Information). Probes printed at a chamber temperature of
Human skin from a 55-year-old male patient, collected in 70°C and build platform temperature of 90°C produced
August 2020, was obtained from the New York Firefighters desirable probes with no warping (Figure S2b, Supporting
Skin Bank at the New York Presbyterian Hospital (USA). Information). The results also indicated that probes
The skin had been dermatomed to a thickness of 0.5 ± 0.1 printed at 30, 50, and 100 µm layer thicknesses produced
mm. This skin was transported in a 10% glycerin solution warping. However, a 200 µm layer thickness produced
and stored at −80°C before conducting any experiments. desirable probes with no warping. Furthermore, warping
Prior to usage, the skin was thawed and rinsed with and surface deformation occurred when the probes were
distilled water for about 45 min to remove any excess printed in the vertical position (Figure S2c, Supporting
glycerin. Our laboratory has previously validated the Information). Conversely, probes printed in the horizontal
storage and preparation methods for dermatomed human position exhibited no warping and only minimal surface
skin, ensuring that the skin retains its structural integrity. deformation (Figure S2b, Supporting Information).
A small round piece of skin (approximately 38.48 mm ) From post-processing optimization, the mean roughness
2
was then cut, dried, and adhered to the SS probe surface (Ra) value of the probes was 7.88 ± 0.00 μm after 1 min
using a Tech-Bond solution (Tech-Bond Solutions, USA) of post-processing, consistent with the reported skin
28
before tack testing. roughness (7.88–16.36 μm). Conversely, the 2-min
post-processing group reported better consistency (i.e.,
2.8. 90° peel adhesion test low standard deviation) and significantly lower Ra (3.90
The TA.XTPlus texture analyzer (Texture Tech ± 0.00 μm), deviating from the reported range for skin
Technologies, USA) was used to perform the 90° peel roughness. Therefore, PP probes post-processed for 1
adhesion test. Strips of PSA-4302 laminates (2.5 × 12.5 min were selected for further studies. Contact angles
cm) were used for analysis. The release liner was removed, for the PP probes measured using de-ionized (DI) water
and laminates were applied to the SS/PP plates. Briefly, and diiodomethane droplets resulted in polar, non-
the SS 900-peel rig with sled (305A; Stable Microsystems, polar, and total SEs of 0.46, 34.16, and 34.62 mN/m,
Texture Technologies Corp., USA) was connected to the respectively. The measured SE of PP probes was found
TA.XTPlus texture analyzer, and the test was performed to be slightly higher than the reported literature value
with pre-test speed: 1 mm/s; test speed: 5 mm/s; post-test (29 mN/m) but was within the SE range for the skin
speed: 10.0 mm/s; test mode: tension; and target distance: (25–56 mN/m). 3D-printed PP plates did not exhibit any
100.00 mm. A graph of force (N) versus distance (mm) was deformation. Hence, the PP plates were not subjected to
generated using Exponent software (Texture Technologies post-processing.
Corp. and Stable Micro Systems, Ltd., USA), displaying the
mean peel force required to detach the PSA laminates from 3.2. Adhesion testing of 3D-printed polypropylene
the SS/PP plates (Figure S3b, Supporting Information). 30 probes, stainless steel probes, and the human skin
Silicone-based adhesive (PSA-4501) was laminated on
2.9. Statistical analyses a backing membrane (9735) with a dry coat weight of 5
All raw data results are expressed as the mean ± standard mg/cm . Probe tack test results revealed no significant
2
deviation of at least three repetitions. A two-way analysis differences in peak adhesive force between the PP probe
of variance (ANOVA) was performed to compare multiple and human skin. Additionally, high variations in the tack

Volume 10 Issue 4 (2024) 520 doi: 10.36922/ijb.3735