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Engineering Science in
Additive Manufacturing TwinPrint: Dual-arm robotic bioprinting

1. Introduction exist. Primarily, large-scale printing has not yet been
realized. Clinically practical sizes need to be achieved
Three-dimensional (3D) bioprinting technology has without extending fabrication time. This requires an
21
facilitated remarkable advancements in the biofabrication array of new approaches such as concurrent printing,
1,2
of complex biomimetic tissues, thus catering to challenges robotic maneuverability, and full system integration and
in organ donor shortage and enabling solutions in automation.
personalized medicine to reduce immune system response.
The most demanding applications for engineered tissues Of note, a vast majority of 3D bioprinting systems
6
3
4,5
include the cartilage, skin, cardiac tissue, vascular involve pre-mixing or post-printing curing protocols, i.e.,
grafts, and hard tissues such as bones. It has also shown bioinks are pre-mixed before loading in a pressure-based
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8
high potential in eliminating dependency on animal extruder, and final crosslinking occurs through curing
testing by introducing artificially constructed organs for processes after printing. This approach, while common, is
pharmacology and pharmaceutical research. 9 not as biologically suitable on the grand scale, due to its
dependency on ultraviolet-based or chemical crosslinking
The heterogeneity and complexity of human tissues
necessitate 3D bioprinting of multi-material and multi- techniques. Soft matter bioinks, such as ultrashort self-
cellular constructs with physical and mechanical properties assembling peptides, are key candidates to explore for 3D
closer to native tissues. This entails the integration of bioprinting due to their instantaneous gelation properties,
10
various biomaterials and cell types to fabricate a single biocompatibility, and nanofibrous topography resembling
17,18,22
biomimetic construct. 11,12 In light of this, several researchers the natural extracellular matrix. While avoiding the
have proposed methods to accomplish the goal of 3D use of harmful crosslinking reagents, their instantaneous
printing multi-material acellular and cellular scaffolds of binding nature requires increased precision control.
varying mechanical properties and print resolutions. Some Screw-driven syringe pump extrusion systems have been
have modified the design of commercial, conventional found to offer better control and flow accuracy when
9,23
3D printers by integrating multiple printheads for multi- working with ultrashort peptides. Our previous research
material 3D bioprinting. 11,13 On the other hand, Liu explored the development of microfluidic syringe pump
et al. and Miri et al. developed their own multi-head 3D extrusion systems embedded with dual coaxial nozzles to
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bioprinter with a rapid switching mechanism for bioink accommodate the gelation nature of peptide bioink. 20,23-25
interchangeability. A handheld multi-material 3D printer Examining the use of articulated robots for 3D
was introduced by Pagan et al. for in situ 3D bioprinting biofabrication applications highlights a number of
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for tissue repair applications. advantages. In comparison to traditional Cartesian 3D
Ultrashort self-assembling amphiphilic peptides are bioprinters, articulated robot workspace is not confined and
compounds with both hydrophobic and hydrophilic can perform successful in situ bioprinting at regions such
regions. 17,18 Peptide Ac-Ile-Val-Cha-Lys-NH (IVZK), as curved or irregular anatomical sites, 26-28 and perform
2
which was investigated in this study for its suitable additional tasks aside from 3D bioprinting, making them
properties belongs to a class of tetrameric ultrashort cost-effective. More significantly, articulated robots offer
self-assembling peptides that was described in detail in additional degrees of freedom, which allows for faster
earlier publications. 19,20 These peptides assemble into fabrication time of highly curved scaffolds with intricate
fibers and further into 3D supramolecular structures in geometry while achieving high deposition precision and
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the form of hydrogels by non-covalent interactions, such printing resolution. Non-planar robotic printing can
as van der Waals interactions and hydrogen bonding. revolutionize 3D bioprinting by breaking away from the
Adding ionic solutions such as phosphate-buffered saline traditional layer-by-layer XYZ approach and creating more
(PBS) to aqueous peptide solutions can accelerate their defined extrusion paths to fabricate complex organs and
fiber formation, reducing gelation times to minutes and tissues. 30-32 A multi-arm configuration running in tandem
seconds, depending on the specific peptide sequence and reduced biofabrication time considerably by increasing the
the peptide concentration. These properties underscore degrees of freedom from the standard 3 axes to 5–6 axes,
the potential of ultrashort self-assembling amphiphilic which would be vital for in situ bioprinting at the clinical
peptides as an optimal bioink material in extrusion-based phase. 33
3D printing and bioprinting, as alternatives to gelatin and Among many challenges facing 3D bioprinting, one
alginate-based bioinks, to facilitate instantaneous layer-by- significant obstacle is achieving reliability and robustness.
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layer printing of acellular and cell-laden material. Currently, 3D bioprinting is hindered by extrusion
With several promising attempts at developing failures, bioink incompatible mechanical and rheological
multi-material 3D bioprinters, certain challenges still properties, and the lack of robust, end-to-end automation.

Volume 1 Issue 4 (2025) 2 doi: 10.36922/ESAM025410025