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

system comprising humectants for a balanced evaporation chosen ink (including particle loading content, cosolvents,
rate, and (iv) controlled print parameters, such as T, R , and additives) is a crucial factor to be considered with respect
f
s. Indeed, all inks investigated required a low s ≤ 0.4 mm/s to the selected cellular lineage.
(at equal CAD patterns), a R in the range of 1.66–4, and a The performance of the microstructures, such
f
T ≥ 40°C (except for Col-based inks due to degradation). as electro-chemical functionalities and mechanical
the particle loaded ones a T ≥ 40°C. From a print strategy characterizations, will be investigated in future application-
perspective, 3D-CJD is recommended for stand-alone driven works. Moreover, future studies will also be focused
free-form complex structures, which do not require strict on a quantitative characterization of the process and
repeatability; a 3D-LBL strategy is preferred for vertically materials, such as the significance of boiling temperature
aligned, multilayered arrays (AR AgNPs ~ 20, AR PEDOT:PSS ~ 4.5, and vapor pressure over the resulting structure. For the
AR Collagen ~ 2.5); and the 3D-PW approach is preferred for collagen inks, a crosslinking approach will be studied, so
complex repeatable geometries, such as lattice units. The as to improve the mechanical properties of the printed
commercial diluted AgNPs-based ink showed the best structures. Furthermore, the use of methacrylated collagen
results in terms of geometrical accuracy, repeatability, (ColMA) combined with UV-irradiation and other noble
and ARs, mostly due to the nature of its particle loading metal NPs-based inks will be assessed for 3D AJ®P.
content and co-solvents chosen. Still, the own formulated
PEDOT:PSS- and the Col-based inks demonstrated good Acknowledgments
abilities at lower ARs, especially with the 3D-LBL and 3D-
PW approach, respectively. Limitations of such inks are The authors gratefully acknowledge the Research
restricted to very complex CAD patterns, which probably Foundation Flanders (FWO) for the doctoral fellowship
require the choice of an instant (in situ) postprinting process granted to Miriam Seiti (1SB1120N) and Olivier Degryse
(e.g., UV-curing). These conclusions are applicable for ink (1S86620N). The authors also acknowledge the Angelo
compositions similar to the ones proposed. For instance, Nocivelli Foundation.
other metallic NPs rather than Ag, such as Cu, Au, Pt , are
[55]
AJ®-printable for 3D-printed electronics via an ultrasonic Funding
configuration, if a similar loading content, particle size and This work was supported by Research Foundation Flanders
shape (spherical, Ø ~ 50 nm), and co-solvent system is used. (FWO) for the doctoral fellowship granted to Miriam Seiti

In general, the main 3D-AJ®P advantages compared (1SB1120N) and Olivier Degryse (1S86620N).
to other AM techniques are: (i) inks versatility for various
applications, (ii) noncontact, maskless printing with Conflict of interest
flexible working distance, (iii) 3D microstructuring down The authors declare no conflict of interests.
to 50 µm, (iv) fast 3D printing time (< 5 min for an array
of 6 × 4 micropillars), (v) high reproducibility and ARs Author contributions
with the 3D-LBL approach, and (vi) complex structures
with the PW approach. Instead, the disadvantages include: Conceptualization: Eleonora Ferraris, Seiti Miriam, Olivier
(i) limited portfolio of commercial optimized AJ®P inks, Degryse
(ii) low reproducibility for CJD approach, (iii) necessity Investigation: Seiti Miriam, Olivier Degryse (for the
of an in situ and postprinting process on the green parts, printing investigation); Rosalba Monica Ferraro,
and (iv) few commercial solutions. Due to a currently Olivier Degryse, Seiti Miriam (for the biocompatibility
limited amount of AJ®P inks in the market (only addressed assays)
to PE), this study gives the basis to develop custom-made Methodology: Eleonora Ferraris, Seiti Miriam, Olivier
3D AJ®P inks, and also prompts toward sustainability, Degryse
biodegradability, and recyclability. Based on the ink Formal analysis: Seiti Miriam, Olivier Degryse
chosen, 3D-printed microstructures can be potentially Writing – original draft: Seiti Miriam
exploited for a vast range of prototypes in life science Writing – review & editing: All authors
(tissue engineering, bioelectronic interfaces), electronics, Ethics approval and consent to participate
and MEMS. Particularly, they may be used in the
assembly step of the manufacturing process of (flexible) Not applicable.
3D-printed electronics, thermo-electrics devices, batteries,
or microelectrode arrays, with special attention on the Consent for publication
surface wettability. More considerations must be taken in Not applicable.
life science applications, in which biocompatibility of the

Volume 9 Issue 6 (2023) 71 https://doi.org/10.36922/ijb.0257