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International Journal of Bioprinting Vector-based G-code generation for biofabrication

using nitrogen, and a print bed movement rate of 30 mm/s files can be quickly converted via drag-and-drop or by
using a 20 G steel needle. opening them from within the program, as shown in
Figure 1C. The EDSTAG simplifies the .dxf to relative
2.10. 2D and 3D extrusion bioprinting G-code conversion, exporting only the necessary relative
Pluronic F-127 (KGaA, Darmstadt, Germany) at a G-code that most devices can interpret, without any
concentration of 30% w/v in water was printed using extraneous commands beyond the coordinates. The
an Inkredible+ bioprinter (Cellink Bioprinting AB, software utilizes the free tool dxf2gcode for the file
Gothenburg, Sweden) equipped with a 25 G conical conversion, automating the process and filtering out
nozzle (Nordson EFD, OH, USA). The different colors unnecessary code for our specific workflow. While the user
were achieved by adding food dye. For the print with the does not need to interact with dxf2gcode directly, it can
fibers, PCL fibers with a size of 15 × 300 µm, produced as remain open for troubleshooting purposes. The direction
described previously, 25,26 were added to the pluronic at a of the paths is shown in the EDSTAG using arrows, and the
2% w/v ratio.
direction can be reversed if needed by selecting the “Invert
2.11. Embedded bioprinting direction” option in the program.
Printing was conducted into a cubical container filled These blocks of code can then be copied into
with the support bath consisting of 1% w/v xanthan Notepad++ and assembled. Notepad++ is modified with
gum (Cosphaderm X34, Cosphatec GmbH, Hamburg, a custom coding language, provided by the authors in
Germany). The ink used was 1% w/v xanthan gum, stained the Supplementary File, to simplify G-code writing, as
with different colorings. Printing was conducted using demonstrated in Figure 1D. This modification allows users
a BioX (Cellink Bioprinting AB, Gothenburg, Sweden) to define collapsible code segments using demarcations
equipped with a 20 G 45-mm long syringe nozzle (Nordson like ;{ and ;} to mark the start and end of each segment,
EFD, OH, USA). respectively. These markers also function as comments,
2.13. Scanning electron microscopy so the machine ignores these lines. This feature improves
The samples were analyzed using a scanning electron the readability of the code, as subroutines can be neatly
microscopy (SEM) device (Crossbeam CB 340 SEM, organized, segmented, and collapsed. Additionally,
Carl Zeiss). collapsible segments within other segments can also
be defined.
3. Results and discussion Each relative G-code block defining a path can be

3.1. General principle and code processing treated as a subroutine. Using relative code makes it
The drawing-coding method involves defining the paths easier to control movement, repetition, multiplication,
that the machine should follow. These paths can be drawn and other actions, while also facilitating the combination
as a continuous line or as several connected segments, with of different path segments and subroutines. Between
the direction and sequence of points specified. The paths subroutines, additional commands—such as absolute
are then exported and converted into relative movement starting coordinates, breaks, speed changes, and pressure
codes in G-code. In this case, we used Adobe Illustrator, adjustments—can be inserted as needed. In most cases,
but other vector drawing software that can export separate the G91 command must be added before the segments to
paths such as .dxf files may also be used. The entire instruct the machine to interpret the code as relative, rather
workflow is straightforward, as illustrated in Figure 1A, than the default G90 for absolute coordinates. Similarly,
starting with drawing the paths as lines in Illustrator. continuous paths can be split into several segments to allow
Illustrator is preferred because manipulating the lines and for the insertion of additional commands between them.
paths is convenient; anchor points can be added to split Since the subroutines are all exported as G-code with G1
or combine paths, as shown in Figure 1B. The direction of movement codes, they can be interpreted by most CNC
the paths can be indicated by adding arrowheads, and the machine-based devices. The device-specific commands
thickness of the lines can be adjusted to simulate the width can be added later, before or after the subroutines, to
of the deposited fiber or strut, making the visualization of assemble the final functional code.
the print more realistic. Additionally, many researchers Additionally, by using the NCnetic plugin, the code
are already familiar with or have experience using this can be visualized in real time, as shown in Figure 1E.
software for creating manuscript illustrations.
After assembling the code, it can be exported as is, or, if
The paths are exported as .dxf files and then converted necessary, extrusion and Z-increase modifiers can be
into relative G-code blocks using the self-developed code added to specific code segments by designating them in
converter “Easy DXF stack generator” (EDSTAG). These Notepad++. This is similar to the previously mentioned

Volume 11 Issue 4 (2024) 212 doi: 10.36922/ijb.6239