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International Journal of Bioprinting Five-axis printer for hybrid 3D scaffolds

incorporated one or two industrial inkjet printheads into water-, solvent-, and particle-based inks with different
robotic arms, while Thalheim et al. developed a six-axis viscosities. Ink supply systems, which can be used in
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robot printer. Shen et al. developed a five-axis platform gravity- or recirculation mode, were selected for all inkjet
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using four single-nozzle printheads, while Gazeau et al. printheads. In addition, the system is equipped with a
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presented a five-axis machine, augmented with a printing self-developed screw extrusion system for highly viscous
block including four industrial inkjet printheads, for large materials and a curing module (FireEdge FE400 UV-LED,
printing applications. Likewise, Urasinska-Wojciket et Phoseon Technology, United States of America [USA]).
al. reported a novel approach to building a hybrid five- The ultraviolet light emitting diode (UV-LED), positioned
axis system using extrusion and single-nozzle inkjet on one side of the printing block, enables printing in
printing for fabricating components with embedded one direction. Alignment and inspection cameras were
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electrical circuitry. integrated accordingly, and the printer was placed in a
With the design, assembly, and configuration of a safety cabinet. The hardware configuration is depicted in
prototype printer, the current work explores the hybrid Figure 1.
fabrication of scaffolds on two fronts. Firstly, the printer 2.2. Software configuration
allows multi-material fabrication of soft phases by The operation of the system requires the use of different
combining two different AMTs: (i) 3D piezoelectric multi- software packages. Mach3, a well-established software
material inkjet printing and (ii) extrusion printing. The for stepper motor control, serves as the control hub for
former is capable of depositing drops of low-viscosity
inks in the picoliter range in a spatially controlled the machine’s motion and reads G-codes stored in NC
manner in a non-contact approach and is ideal for future files. The communication with the inkjet printheads is
biofabrication. Conversely, extrusion printing is a well- achieved through a software development kit, providing
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established AMT for tissue engineering scaffolds and is control over the different printhead families. An in-
especially suited for printing highly viscous hydrogels, house-developed graphical user interface enhances user
mimicking the extracellular matrix (ECM). Secondly, the interaction and enables the loading of pre-sliced STL
printing module is integrated into a system with five-axis files (in bitmap format) and the configuration of inkjet
capabilities, which allows printing on curved surfaces to printing parameters (e.g., waveform, jetting frequency, and
fabricate hybrid scaffolds of dissimilar materials. Our temperature of the printheads).
methodology follows a step-by-step progression through 2.3. Materials
different levels of complexity by hybridizing soft and pre- A low-viscosity photocurable resin (for inkjet printing)
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fabricated hard phases in three different use cases for and a high-viscosity amphiphilic peptide hydrogel
osteochondral and palatal scaffolds printed on planar, (PuraStat RADA16, 3D-Matrix, France) capable of self-
single-curved, and free-form surfaces. Our findings could assembling into fibrils 33,34 (for extrusion printing) were used
potentially facilitate personalized scaffold fabrication and as soft-phase materials. WSS 150 (Stratasys Ltd., Israel)
TM
surpass conventional mono-material linear three-axis was used as support material for inkjet printing. Substrates
printing strategies, widening the potential of 3D printing that resembled hard phases were printed out of PLA
for the fabrication of hybrid scaffolds.
fabricated by FFF (Bambu Lab Ltd.) and hydroxyapatite
2. Materials and methods fabricated by lithographic ceramic manufacturing (Lithoz
GmbH, Austria).
2.1. Hardware configuration
A commercially available three-axis computer numerical 2.4. Methodology for hybrid printing and non-
control (CNC) portal system (High-Z S720T, CNC Step, planar inkjet printing
Germany) was augmented with a two-axis rotating gantry, Sequential hybrid printing is explored through three
and each axis was coupled to additional stepper motors different strategies in matching use cases. Pre-fabricated
to control the rotation angles. Designed originally for 3D-printed parts, exhibiting topologies from planar to
industrial tasks like engraving, milling, drilling, and curved surfaces, served as hard phases. The first strategy
cutting, the three-axis CNC portal serves as the base to is a hybrid approach that combines inkjet and extrusion
bear the weight of the hardware components required printing on planar surfaces for soft and hard material
for a fully equipped hybrid inkjet-extrusion printing interfaces; the second strategy employs multi-material
system. Our setup incorporates three different families inkjet printing on a single-curved surface, specifically
of inkjet printheads (Ricoh MH2820, Ricoh MH5421F, addressing scaffolds for osteochondral defects; the third
and Xaar 1003) controlled by driver electronics for the strategy involves mono-material inkjet printing on a free-
processing of different materials, including photocurable-, form surface for palatal defect scaffolds. Each case was

Volume 10 Issue 3 (2024) 590 doi: 10.36922/ijb.3189