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

fabrication (FFF), and bioprinting. Despite their geometries, unusual infill patterns, irregular printing
5,6
3,4
versatility, these machines require carefully choreographed sequences, etc., which were not conceived/predicted by
movements, necessitating the creation of corresponding the developers. Despite the ability to precisely tune the
movement codes. The standard input for these machines printing parameters by adding breaks, printhead swaps
is G-code, which combines machine-specific commands or modifying extrusion/pressure on certain parts of the
with movement instructions for the axis motors. These print are often not granted. This leaves the users without
movements are typically input as coordinates, either any reasonable alternatives for achieving/fine-tuning their
absolute or relative, meaning that the system must generate desired print.
or deduce the trajectory that the machine should follow. Alongside the challenge of generating G-code, there
4
For simple movements, such as bioprinting evaluation is a lack of standardized approaches compatible with the
patterns or basic MEW grids, it is possible to manually diverse machines used in biofabrication. 14,17–19 For example,
7–9
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write coordinates. However, this approach becomes while both bioprinters and MEW devices are three-axis
cumbersome, prone to errors, and time-consuming, CNC machines, their G-code generation methods differ
particularly when scaling or adjusting complex shapes. significantly. This means that operators must relearn how
In these cases, parametric coding is often used, where to generate codes for each device, complicating the transfer
mathematical functions allow for quick adjustments such of designs and hindering the convergence of different
as scaling, rotating, or adding grids by modifying a few fabrication techniques into a unified system. Converging
parameters. However, while parametric methods are these methods is essential for biofabrication, as tissues
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effective for certain geometries, they face challenges with are hierarchical structures that require precise control at
programming complex shapes, non-repetitive elements, multiple scales. 20–22 Achieving this integration allows for
and high precision. Furthermore, these methods often the accurate fabrication of complex tissues, from micro-
require significant mathematical competence and may scale cellular patterns to macro-scale tissue layers.
not be compatible with all machines, making them less
flexible. Some programs, such as Full Control G-code, Additionally, using absolute coordinates makes
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allow for the generation of code for specific shapes but are transferring designs or adjusting starting positions
still limited in their ability to handle irregular or highly challenging, as each coordinate needs recalculating
complex designs. or re-slicing the object entirely. This highlights the
need for more adaptable, standardized approaches
Some academic groups have developed G-code to streamline the transfer of designs across different
generators for bioprinting and MEW based on algorithmic biofabrication techniques.
shapes of a geometrical unit repetition/in sequence 13–15 ;
however, these tools lack in freedom of designing un- We present a versatile and intuitive method for
patterned and irregular shapes, or shapes that were not generating G-codes by drawing paths in vector-based
considered by the developers. On the other end of the programs, such as Adobe Illustrator. These paths are
spectrum are 3D shapes, for which slicers are commonly converted into relative G-code blocks and assembled into
used, such as those employed in fused deposition modeling the final script using the text editor Notepad++, where
(FDM) 3D printing. The slicer converts a 3D mesh into a machine-specific commands and necessary instructions
sequence of horizontal paths that the machine follows to are added. This approach provides full control over
fabricate the object, optimizing the trajectory based on the shapes, enabling the quick generation of both simple and
slicer’s established parameters for efficient production. complex geometries, while allowing easy adjustments and
9,16
While these slicers are useful for regular FDM 3D printing, parameter changes. It is user-friendly, making it accessible
they are limited by their design parameters and cannot be to less experienced users without deep programming
easily adapted for other biofabrication techniques where knowledge, and streamlines the process, reducing time
more control is required. For example, while there may on development, and troubleshooting. Although paths are
be parallels between FDM and 3D extrusion bioprinting, drawn in 2D, stacking layers or modifying designs allows
the paths and deposition patterns for plastic FDM- for 3D constructs, facilitating complex structures.
printed objects are vastly different from those required Herein, we demonstrated the new method’s advantages
for bioprinted tissues, especially considering factors like and precision in various biofabrication techniques,
cell orientation and material properties, limiting the use including MEW, FDM, freeform printing, and bioprinting.
of FDM slicers for bioprinting applications. While some This approach ensures flexibility and control, enabling
bioprinters also have their own integrated slicing software the creation of intricate geometries and precise patterns
that is better adapted to bioprinting, the programs still tailored to each technique. It also promotes convergence in
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falter when attempting to produce complex printing biofabrication by facilitating code transfer across different

Volume 11 Issue 4 (2024) 210 doi: 10.36922/ijb.6239