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International Journal of Bioprinting Biocompatible materials and Multi Jet Fusion

behavior (G’ > G’’) until G’/G’’ cross over. Expectedly, a
lower gelatin content corresponded to the cross-over at
lower strain rates, while higher gelatin content resulted
in higher values of G’. Hydrogels with 3.0% and 5.0% of
gelatin showed a slight increase in the storage modulus
followed by a steep downward slope. From the above
results, the gelatin content was set at 4.0%.

Subsequently, amplitude sweep tests were performed on
bioinks with varying alginate content (0.5%, 0.75%, and 1.0
%) (Figure 4). Bioink B revealed the highest constancy in G’
values resulting in a broad linear viscoelastic (LVE) region.
Figure 2. Flow curves of bioinks A, B, and C.
Interestingly, bioinks D and E with higher alginate content
and the bioink is liquid. Bioink A reached its lowest revealed a similar spike in G’ as observed for bioinks A and
G’/G’’ at 32.3°C. Bioinks B and C obtained similar G’/G’’ C. Bioinks B, D, and E reached G’/G’’ crossover at 239%,

values at 33.1°C and 33.3°C, respectively. These bioinks 340%, and 396% strain, respectively. The 0.75% alginate
also had higher values of both, storage and loss modulus, content was selected for further analysis.
particularly in the temperature range of 20°C to 35°C.
The next step involved testing bioinks with fixed gelatin
Bioink flow analysis with gelatin content from 3.0% to
5.0% enables the estimation of printability (Figure 2). All (4.0%) and alginate (0.75%) contents but varying CCNC
concentrations (bioink D, 1.4%; bioink F, 1.0%; and bioink
bioinks exhibited a shear-thinning behavior, in which shear G, 2.0%) using the amplitude sweep test (Figure 5). There
rate (γ) increases and shear stress (τ) decreases viscosity was a significant increase in G’ with increasing CCNC
(η). In the conducted research, the viscosity range for all concentration, but the increase in G’’ was less noticeable.
bioinks was similar. It was 2863–0.08 Pa·s for bioink A, This could be explained by the hydrophilic properties
4630–0.02 Pa·s for bioink B, and 5210–0.05 Pa·s for bioink of CCNC that contribute to an overall increase in the
C at a shear rate range of 0.01–200.00 s .
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solid component of the bioinks, resulting in elevated G’.
In the amplitude sweep test, bioinks with varying Bioinks F, D, and G reached the G’/G’’ crossover at 366%,
concentrations of each component were tested, beginning 340%, and 256% strain, respectively, demonstrating
with bioinks with different gelatin content (3.0%, 4.0%, the improvement of shear-thinning properties with the
and 5.0%) (Figure 3). All bioinks displayed a solid-like addition of CCNC.

Figure 3. The results of amplitude sweeps of bioinks A, B, and C (increasing gelatin content: 1.0%, 1.4%, 2.0%).

Figure 4. The results of amplitude sweeps of bioinks B, D, and E (increasing alginate content: 0.5%, 0.75%, 1.0%).

Volume 9 Issue 1 (2023) 5 https://doi.org/10.18063/ijb.v9i1.621