Page 73 - IJB-9-6

International Journal of Bioprinting 3D Aerosol Jet® printing for microstructuring

®
3D AJ P results on PEDOT:PSS-based ink Poor quality results
CJD c LBL (own formula) d
a
Standard formula 250 µm

250 µm
e
b
Own formula 250 µm

250 µm 250 µm 250 µm

Figure 4. Results for the 3D AJ®P of microstructures for PEDOT:PSS-based ink, along with print strategy and characterization. (a) Standard formula
and (b) own formula of 3D-CJD PEDOT:PSS-based ink; (c) own formula of 3D-LBL PEDOT:PSS-based ink. (d, e) Poor-quality results for 3D-LBL
PEDOT:PSS-based ink own formula.

structures. Instead, Figure 3c and d highlight defected rough surface (Figure 4e), which was caused by a fast water
pillars printed with the diluted ink, which have fractures evaporation, with the water content in the ink higher than
that increase in intensity and dimension as print layers in the AgNPs-based ink.
increase. This result is caused by the use of a s LBL, AgNPs =
1 mm/s, that is 2.5 faster than the previous one, and it Figure 4d and e depict poor-quality results obtained by
is visible both in the configuration with a doubled CAD 3D-LBL of PEDOT:PSS-based ink. In particular, Figure 4d
circle (Ø = 100 µm, Figure 3c), and the previous one (Ø = shows the printing of a set of five micropillars with a
50 µm, Figure 3d). higher R , = 5 (instead of 2), by using a higher
f LBL, PEDOT:PSS
SGF = 50 sccm (instead of 35 sccm) and a lower
3.2. PEDOT:PSS-based ink CGF LBL, PEDOT:PSS = 10 sccm (instead of 18 sccm). All the
LBL, PEDOT:PSS
The second type of ink explored is PEDOT:PSS-based. other parameters were kept the same. Similar to what
Table 2 summarizes the print parameters. As reported was observed with the AgNPs-based ink, the effect of the
in Figure 4, only the own-formula combined with the SGF, which forces the bending of pillars and diverses the
adoption of the 3D-LBL technique was successfully printed aerosol jet direction (especially at higher print layers),
in 3D structures. Figure 4a and b show the 3D-CJD AJ®P was significant. Moreover, since the CGF was almost half
of micropillars bent more than 130 ° printed with both of the previous one, the diameter of pillars was reduced
inks and at a low process reproducibility. Instead, Figure 3c by ~ 47%, with an average diameter of 26.64 ± 4.92 µm.
shows an array of 3D-LBL AJ®-printed micropillars with Furthermore, as previously anticipated, the change in
a compact internal structure, with an average height the platen temperature can also have a significant effect:
of 256.25 ± 5.26 µm (50 layers), a diameter of 56.79 ± Figure 4e indeed illustrates the printing of 5 micropillars
4.79 µm, for a maximum AR = 4.5 (printing time ~ 5 min, at T LBL, PEDOT:PSS = 100°C (instead of 80°C), with n = 25.
see Videoclip S2). These structures were 3D-printed at the From the image, it is clearly visible a rougher and more
same print speed of the AgNPs-based diluted ink, but the deformed surface than the set of pillars reported in
achievable accuracy was lower. The possibility to obtain Figure 4c, with an average pillars diameter equal to 39.13 ±
poly-branches was also rare, most likely due to a higher 4.03 µm, that is ~ 30% thinner than the one printed at
ink viscosity. Furthermore, the platen temperature was set T LBL, PEDOT:PSS = 80°C. As previously observed with the
at T PEDOT:PSS = 80°C, which is 20°C lower than the one used AgNPs-based ink, also in the case of this PEDOT:PSS-
for the AgNPs-based ink, T LBL, AgNPs = 100°C, since lower based ink, only specific parameter conditions allow a
ones did not allow the building up of 3D structures (as repeatable and uniform 3D AJ®P. Further studies will
3D-CJD), and higher ones produced thin pillars with a analytically and systematically investigate this statement.

Volume 9 Issue 6 (2023) 65 https://doi.org/10.36922/ijb.0257