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Lee, et al.
in the space surrounded by the printed ink. Based on the without any support. Thus, it is important to ensure that
rheological characterization, Ink C exhibited the lowest the yield stress and storage modulus are sufficiently high
yield stress and storage modulus; Ink C exhibited more to allow the ink to self-support themselves on deposition.
lateral spreading than Inks A and B. In crucial constant, These observations confirmed the printability of Ink A
no lateral spreading of ink was observed for structures that was suitable to create 3D food structures.
printed with Inks A and B; the printed structures were well
maintained. Despite the good printability, we observed 4.4. Texture profile analysis
the phase separation of the oil from the structures We characterized the textural properties of the inks. We
printed in Ink B over time, which was also previously printed mesh structures with the dimensions of 20 mm ×
characterized (Figure 1). While the current study focused 20 mm × 20 mm with Inks A, B, and C and performed
on characterizing the rheological properties of different a double compression test to mimic the biting behavior
coconut inks for their printability, other parameters of humans. The hardness decreased from 0.60 N (Ink
such as dispensing pressure, nozzle velocity, and nozzle A) to 0.35 N (Ink C) and the chewiness also decreased
diameter would affect the dimension of the printed inks,
which is essential to achieve print fidelity . Overall, from 0.33 (Ink A) to 0.14 (Ink C), which correlated to
[44]
we identified that Ink A was the promising candidate to the increase in water content (Table 2). As the oil content
perform cold extrusion to create complex 3D structures. increased, there was no significant change in hardness
Finally, we demonstrated the fabrication of various and chewiness between Ink A and B. There were no
3D structures with Ink A using the DIW printer. All printed significant changes in adhesiveness and cohesiveness
structures are shown (Figure 3). The deposited inks of the inks in response to the addition of neither oil nor
exhibited structural integrity, and all printed structures water for the range of parameters we investigated.
were self-supporting. In this demonstration, we also TPA suggested that hardness and chewiness could
printed a humanoid structure with overhang features and be varied by adding water. However, the rheological
the deposited material was able to maintain the structure properties of the inks would be simultaneously
compromised, which affected the printability of the inks.
For example, the hardness of structures printed with Ink C
A B was lower than that of Ink A but the rheological properties
of Ink C were not adequate for 3D printing, which
caused the inks to spread on deposition (Figure 2C). The
previous studies reported that textural properties could be
controlled by varying geometrical and process parameters
such as infill density and nozzle diameter . Overall, the
[45]
desired textural properties should be achieved by altering
material properties as well as designing the structures of
the printed material, which are under investigation.
C D
5. Conclusions

This paper discussed the 3D printing of coconut
cream added with coconut oil using a DIW 3D printer.
3D-printable coconut cream inks were formulated with
additional coconut oil without causing oil separation,
and 3D structures were fabricated at room temperature.
We conducted oil separation tests to determine the limits
Figure 3. DIW 3D printed models with coconut cream ink A. (A) of the amount of oil that could be added into the inks at
humanoid, (B) wheel, (C) pyramids, and (D) dragon (All scale different water concentrations because the stability of the
bars: 5 mm) ink was crucial to ensure smooth extrusion of material.

Table 2. Texture profile analysis of coconut cream inks. All values were calculated as means (± standard deviations).
Sample Hardness (N) Adhesiveness (mJ) Cohesiveness Chewiness Index
25% water with 10% (w/w) oil (Ink A) 0.60 ± 0.02 a 2.95 ± 0.35 a 0.48 ± 0.02 a 0.33 ± 0.01 a
25% water with 12.5% (w/w) oil (Ink B) 0.51 ± 0.08 ab 2.30 ± 0 a 0.46 ± 0.03 a 0.23 ± 0.06 ab
33% water with 10% (w/w) oil (Ink C) 0.35 ± 0.02 b 2.25 ± 0.21 a 0.42 ± 0.06 a 0.14 ± 0.04 b
a,b,c Means that do not share a superscripted letter are significantly different at p<0.05
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