Annals of 3D Printed Medicine 18 (2025) 100201
Contents lists available at ScienceDirect
Annals of 3D Printed Medicine
journal homepage: www.elsevier.com/locate/stlm
Research paper
Affordable multicolor 3D printing solution for biomedical education in lowand middle-income countries
Dat Minh Lu a,b,** , Phong Van Dong c, Hien Bui Thu Hoang d , Dang Ngoc Tran e,b,
Khiem Tran Dang f,g, Linh Thanh Duy Tran a,h , An Le Pham a,b,i,*,**
a
Family Medicine Center, Faculty of Medicine, University of Medicine and Pharmacy at Ho Chi Minh city, 217 Hong Bang St, Ward 11, District 5, Ho Chi Minh city,
700000, Vietnam
Grants and Innovation Center, University of Medicine and Pharmacy at Ho Chi Minh city, 217 Hong Bang St, Ward 11, District 5, Ho Chi Minh city, 700000, Vietnam
c
Faculty of Mechanical Engineering, Ho Chi Minh City University of Technology, 268 Ly Thuong Kiet St, Ward 14, District 10, Ho Chi Minh city, 700000, Vietnam
d
Department of Radiology, Cho Ray Hospital, 201B Nguyen Chi Thanh St, Ward 12, District 5, Ho Chi Minh City, 700000, Vietnam
e
Department of Environmental Health, Faculty of Public Health, University of Medicine and Pharmacy at Ho Chi Minh city, 217 Hong Bang St, Ward 11, District 5, Ho
Chi Minh city, 700000, Vietnam
f
Department of Surgery, University of Medicine and Pharmacy at Ho Chi Minh city, 217 Hong Bang St, Ward 11, District 5, Ho Chi Minh city, 700000 Vietnam
g
Dept of Gastrointestinal Surgery, Nguyen Tri Phuong Hospital, 700000, Vietnam
h
College of Medicine, Taipei Medical University, Taipei, 110, Taiwan
i
Child Health Research Centre, The University of Queensland, Sir Fred Schonell Drive, Brisbane, Queensland, 4072, Australia
b
A R T I C L E I N F O
A B S T R A C T
Keywords:
Three-dimensional
Fused deposition filament
Water-soluble
Multicolor
Education
anatomy
3D printing for biomedical education in universities remains largely inaccessible in low- and middle-income
countries (LMICs) due to the high cost of commercial material jetting and powder bed fusion 3D printers. To
address this barrier, we have developed an affordable multicolor fused deposition modeling (FDM) 3D printer
capable of producing biomedical models with intricate geometries. The key innovation of our printer is the novel
integration of two distinct hybrid printhead configurations to enable simultaneous multicolor printing and watersoluble support material deposition. Positioned along the same X-axis, the first printhead employs a filament
cutting, retracting, and purging mechanism to print in seven colors, while the second printhead is dedicated to
printing water-soluble support material. The printer utilizes a hybrid CoreXY kinematic system and offers a 30 ×
30 × 30 cm print volume. Its operations are controlled by two MKS Monster8 V2.0 boards and an MKS Pi V1.1
running Klipper firmware, with Orca Slicer software converting 3D model data into printer-readable instructions.
Our printer successfully operated for up to 45 h, producing four detailed heart models (18 × 15 × 10 cm) and a
multicolor DNA polymerase model from online databases and CT scan images. Support structures were removed
by immersing the prints in warm water for 24 h, ensuring precise structural integrity for complex models. By
combining multicolor printing with water-soluble support material, our cost-effective, frugal innovation allows
the fabrication of intricate, vibrant biomedical models, making 3D printing more feasible for biomedical edu­
cation and research in LMICs.
1. Introduction
1.1. Application of biomedical models
Biomedical models are usually used for teaching, learning, and
practicing in health science fields such as medicine, biology, and ge­
netics. Healthcare practitioners can enhance their ability to strategize
and implement intricate surgical operations, hence mitigating the like­
lihood of complications and enhancing patient outcomes through the
development of precise and tailored models designed for individual
* Corresponding author at: Child Health Research Centre, The University of Queensland, Sir Fred Schonell Drive, Brisbane, Queensland, 4072, Australia.
** Corresponding author at: Family Medicine Center, Faculty of Medicine, Grants and Innovation Center, University of Medicine and Pharmacy Ho Chi Minh city,
217 Hong Bang St, Ward 11, District 5, Ho Chi Minh city, 700000, Vietnam.
E-mail addresses: luminhdat@ump.edu.vn (D.M. Lu), dongvanphong1908@mail.com (P. Van Dong), hoangbuithuhien@gmail.com (H.B.T. Hoang),
tranngocdang@ump.edu.vn (D.N. Tran), khiemdangtran@yahoo.com (K.T. Dang), tranthanhduylinh@ump.edu.vn (L.T.D. Tran), phamlean@ump.edu.vn
(A.L. Pham).
https://doi.org/10.1016/j.stlm.2025.100201
Received 31 October 2024; Received in revised form 19 February 2025; Accepted 17 March 2025
Available online 3 April 2025
2666-9641/© 2025 The Authors.
Published by Elsevier Masson SAS. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/).
D.M. Lu et al.
Annals of 3D Printed Medicine 18 (2025) 100201
patients [1]. Moreover, medical education is significantly influenced by
the utilization of 3D printing. Traditionally, learning and teaching have
relied on materials such as atlases, screen visualizations, 3D models
created using the casting process, and cadavers. Nevertheless, the
scarcity of cadavers and the use of hazardous chemicals in their pres­
ervation process may render them unsuitable for medical instruction.
The presence of these compounds has the potential to cause health
problems, including irritation of the skin and airways, and an increased
risk of infection [2,3]. Furthermore, the current accessibility of 3D
models produced by injection molding methods is limited in terms of
both design and quantity, thus falling short of achieving desired
educational objectives. Anatomical 3D printing allows for the creation of
precise 3D models of patient-specific anatomies in a flexible manner
which are applied for educational purposes, surgical planning (visuali­
zation, practicing intervention), external parts, surgical instruments,
and internal implants [4]. A systematic review has revealed that seven
research studies employing 3D printed anatomical models in surgical
procedures demonstrated a mean time saving of 62 min per case. This
translates to a cost saving of $3720 per case due to reduced operating
time. Based on these findings, it was estimated that a minimum of 63 3D
printed models or guides per year, equivalent to 1.2 per week, would be
necessary to offset the annual fixed costs of utilizing this technology [1].
A review of the literature on medical education found that students
who learned using 3D printing models had better test performance,
found the 3D models more useful, achieved higher test accuracy, and
expressed greater satisfaction with their learning compared to a con­
ventional group that studied using cadaver and 2D models [5].
3D printing of biomolecular models can also aid research and
pedagogy fields. A survey showed that 3D printing helps improve stu­
dent engagement in class as well as overall grade of biochemistry course
[6]. Biomolecular models help connect abstract or invisible structures to
human comprehension by offering tangible representations at a scale
that is perceivable to humans [7]. Therefore, the integration of 3D
printing technology into health science education is of utmost impor­
tance in the 21st century.
required, which is impractical for intricate models with deep cavities
and risks structural damage. These constraints limit its suitability for
multi-color biomedical models with complex internal geometries, where
both structural integrity and accurate anatomical representation are
essential.
FDM, in contrast, is an affordable and widely accessible technology
that has been extensively used in LMICs for biomedical education and
surgical planning [9]. In FDM 3D printing, thermoplastic filament is
heated and extruded through a nozzle to build models and support
structures layer by layer. To enhance its suitability for biomedical model
production, an ideal FDM 3D printer must meet two critical
requirements:
1. Multicolor printing – The ability to print in at least seven distinct
colors is necessary to differentiate intricate anatomical and
biochemical structures using a single material, typically polylactic
acid (PLA).
2. Water-soluble support material printing – The capability to print
support structures using polyvinyl alcohol (PVA), which dissolves in
water post-printing, ensuring the integrity of models with complex
geometries.
FDM technology can be optimized to meet these requirements, of­
fering a cost-effective and practical solution for biomedical education
and research.
1.3. Limitations of existing FDM 3D printing technology for biomedical
model printing
Most commercially available FDM 3D printers offer either multicolor
printing or water-soluble support material printing, but few efficiently
integrate both in a single system. Some printers, like the Bambu Lab X1Carbon and A1 Mini, achieve multicolor printing by switching filaments
through a single extruder, but they cannot reliably print with watersoluble materials. Other printers, such as the Sovol SV04 (SPIXI ENT.,
Shenzhen, China), utilize two independent extruders (IDEX), while
models like the Ultimaker S5 (Ultimaker Co., Zaltbommel, The
Netherlands) employ two direct extruders mounted on the same car­
riage. These configurations allow PLA and PVA printing within a single
job, but color capability is typically limited to two or fewer. Such limi­
tations pose significant challenges when attempting to combine both
multicolor printing and water-soluble support materials in biomedical
3D printing, where color differentiation and soluble supports are crucial
for complex geometry models.
A single-extruder setup, while capable of switching colors, is un­
suitable for printing both polylactic acid (PLA) and polyvinyl alcohol
(PVA) together. This approach requires excessive purging during ma­
terial transitions, leading to high PVA wastage and increasing the risk of
nozzle clogging due to the heterogeneity of materials, which reduces
printing reliability. On the other hand, independent dual extruders
systems can print PLA with PVA separately, but they often lack multi­
color capabilities. A tool-changing 3D printer, such as the Original Prusa
XL, allows multiple printheads to switch using a docking mechanism,
enabling the printing of up to four colors and water-soluble support
material. However, this design requires a larger physical footprint, limits
the number of printheads (typically to fewer than six), and demands
precise calibration and increased hardware complexity, thus raising
labor, maintenance time, and operating costs.
Several studies have explored biomedical 3D printing using either
multicolor printing or water-soluble support materials, but rarely in
combination. For example, a two-color prostate cancer model was pro­
duced using dual extruders FDM 3D printing with no water-soluble
support material for just $20 [10]. Other studies have demonstrated
the printing of single-color abdominal aortic aneurysms and heart
models with water-soluble support materials, but at the expense of
multicolor capability [11,12]. Additionally, Eduardo [7] developed a
1.2. Low-cost 3D printing solutions for biomedical models
3D printing, also known as additive manufacturing, enables the
creation of three-dimensional objects by depositing material layer by
layer, allowing for the production of complex geometries with minimal
waste. Several 3D printing technologies exist, ranging from low-cost
methods, such as fused deposition modeling (FDM) and vat photo­
polymerization, to high-cost, advanced systems, such as material jetting
and powder bed fusion. Material jetting uses a printhead to dispense
photopolymer materials that are cured by UV light while also incorpo­
rating water-soluble support material, allowing for full-color, high-res­
olution prints with varied mechanical properties. Powder bed fusion
selectively fuses powdered materials, such as metals or plastics, using a
heat source like a laser or electron beam. This technology can incorpo­
rate an inkjet printhead to enable full-color printing, and the powder bed
acts as a support structure, eliminating the need for cutting off the
support pilars [8]. However, the acquisition and maintenance costs of
these printers are high, making them impractical for use in LMICs.
Vat photopolymerization 3D printing technology is a widely
employed in medical applications, valued for its high resolution and
precision. This process utilizes ultraviolet (UV) light to selectively cure
liquid photopolymer resin, enabling the layer-by-layer fabrication of
complex geometries. The technology is available across a broad price
spectrum, with entry-level systems such as the Elegoo series costing a
few hundred USD, while industrial systems such as Formlabs can exceed
several thousand USD. Despite its advantages in surgical guide fabrica­
tion, vat photopolymerization has significant limitations for biomedical
model production. It is monochromatic, lacks water-soluble support
materials, and requires labor-intensive post-processing. Support struc­
tures must be manually removed, and post-printing colorization is
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Annals of 3D Printed Medicine 18 (2025) 100201
protocol for printing biomolecules using a low-cost FDM 3D printer with
only one color and no water-soluble support material.
To the best of our knowledge, there is a significant gap in the liter­
ature on FDM 3D printing that combines multicolor printing with watersoluble support material in a single process. This limitation restricts the
ability to create detailed, high-fidelity biomedical models essential for
educational and research applications. Thus, our primary objective is to
modify the FDM 3D printing process to enable the simultaneous printing
of up to seven colors along with water-soluble support material, over­
coming the constraints of existing technologies.
PVA, a secondary printhead is added on the same gantry. Each printhead
can independently move along the X-axis. This setup is known as inde­
pendent extruder (IDEX) (Fig. 2B). The integration of a multicolor
printhead and IDEX creates a novel configuration, which we call DAPHybrid-IDEX (Fig. 2A). Each printhead is equipped with two CR-10
hotends (Shenzhen Creality 3D Technology Co., Shenzhen, China),
which have a nozzle diameter of 0.4 mm.
2.1.2. The integration of both direct drive extruder and Bowden extruders:
hybrid extrusion
Our constructed printer, the DAP V1, features a multicolor printhead
equipped with one direct drive extruder and seven Bowden extruders.
We call this configuration “Hybrid extrusion”. A direct drive extruder is
a stepper motor attached to a extruder kit located right above the
printhead that regulates the process of introducing filament into the
nozzle (Fig. 1A). A Bowden extruder, on the other hand, involves a
stepper motor that drives the filament through a plastic tube, known as a
Bowden tube (Fig. 1B). Seven Bowden extruders (NEMA 17 42CM04,
Leadshine Technology Co., Shenzhen City, Guangdong Province, China)
propel seven filaments through the filament splitter into the direct drive
extruder, and subsequently into the nozzle. After each color change, the
direct drive extruder synchronizes its rotational motion with the cor­
responding activated Bowden extruder. In other words, the Bowden
extruders are responsible for filament transition, while the direct
extruder is responsible for precise control of material flow during the
printing process (Fig. 1C). On the other hand, the secondary printhead
responsible for printing water-soluble support material is equipped with
only a direct drive extruder. Two direct extruders are dual drive stepper
motors (NEMA 14 36HS2418CL16, GIBOH, NBLINGKAI Manufacturer).
2. Method
2.1. Two innovative approaches of our DAP V1 multicolor 3D printer
system
2.1.1. The integration of ten-inlets-one-outlet multicolor printhead and
independent extruders (IDEX) technology
To enable printing in multiple colors using a single material (PLA), a
single nozzle printhead is mounted on a mobile gantry equipped with a
filament changing mechanism. Filaments are driven into the filament
splitter, which has ten inlets and one outlet. This configuration allows
for printing in a maximum of ten colors (Fig. 1C). When the filament
change sequence is initiated, the printhead moves to the stationary
sharp blade positioned on the front gantry of the printer, to sever the
molten filament before withdrawal (Fig. 4C). Retracting molten filament
into the filament splitter without trimming may lead to potential fila­
ment jamming. The subsequent filament is propelled through the fila­
ment splitter and directed into the hot nozzle. A small section of filament
is purged out to prevent color contamination from the preceding
filament.
To enable the printing of water-soluble support material, specifically
Fig. 1. Types of extrusion system.
Footnotes: A. Direct extrusion. B. Bowden extrusion. C. Our DAP printer with “Hybrid extrusion”.
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Annals of 3D Printed Medicine 18 (2025) 100201
Fig. 2. Multi-color, multi-materials nozzle configuration.
Footnotes: A: Our “DAP-Hybrid-IDEX”, B: IDEX, C: tools changer, D: single nozzle with filament splitter, E: Fixed multiple nozzles on a printhead.
2.2. Printer kinematics and electronics
source [13]). The movement of the build platform in the Z-axis direction
is also driven by two stepper motors. The model of all stepper motors
that drive the X, Y, Z axes is NEMA 17 42CM04 (Leadshine Technology
Co., Shenzhen City, Guangdong Province, China). Two MKS Monster 8
V2 controller boards, along with a MKS Pi V1.1 (Makerbase, Guangzhou,
Guangdong, China) loaded with an open-source firmware Klipper
V0.12.0, are used to control the printer. A web-based application,
Mainsail (BIGTREETECH, Shenzhen, China) acts as a control interface
The hybrid CoreXY kinematic is chosen for the motion mechanism of
the printer’s components. Four closed-loop stepper motors were set up
by wiring four MKS-SERVO42C-V1.0 drivers (Makerbase, Guangzhou,
Guangdong, China) to four stepper motors, which are used to operate
the mobile gantry along the Y-axis direction and to move the two
printheads along the X-axis direction on the mobile gantry (Fig. 3,
Fig. 3. Hybrid CoreXY kinematics.
Footnotes: Y1, Y2: stepper motors for moving the printheads-carriage gantry along Y-axis direction. X1, X2: stepper motors for moving two printheads along X-axis
direction on the moving gantry. P1: Multicolor printhead (PLA). P2: Printhead printing water-soluble support material (PVA). (Source [14]).
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Annals of 3D Printed Medicine 18 (2025) 100201
for the printer. After assembly, the two printheads may not be properly
aligned in terms of their printing positions. To achieve precise alignment
of the printhead positions in relation to each other, the printer must
undergo printhead offset calibration. Finally, our innovative multicolor
3D printer prototype, named DAP V1 (Fig. 4), has been completed. The
breakdown of machine cost is shown in Table 1.
was subjected to a thickness of 2 mm. The outer boundary of the left
ventricular myocardium and the interventricular septum were
segmented using “Surface cut” tool. This allowed us to segment the
entire block of the left ventricle and myocardium. "Logical operators"
were used to segment the left myocardium by subtracting the left
ventricle from the entire block. The segmentation of coronary arteries
was performed using the “Paint” tool, with a threshold range of 300 to
870 HU. Subsequently, the arteries’ diameter was augmented by 1 mm
using the ’Margin - Grow’ tool to replicate the artery wall. The cardiac
valves were segmented by using the “Paint” tool, with intensities
ranging from 100 to 400 HU (Fig. 5). The 3D model was partitioned into
the upper and lower parts. The cut plane is positioned slightly below the
plane that encompasses the mitral annulus. The magnetic joints were
ultimately designed for assembling the two components of the model
within the Meshmixer V3.5 software (Autodesk Inc., CA 94105 USA).
2.3. 3D data preparation
2.3.1. Heart failure model generated from a CT scan of a real patient
An anonymous female patient diagnosed with heart failure and
ischemic heart disease underwent an ECG-gated computed tomography
coronary angiography with intravenous contrast using a 128-detectorrow CT scanner (Siemens Healthineers Inc., Leipzig, Germany), with a
120 kV voltage and 0.5 mm slice thickness. Images of the diastolic phase
were captured and stored in DICOM format, then imported into the 3D
Slicer software. 3D Slicer is an open-source medical imaging software,
with many advanced visualization features used in biomedical fields
worldwide [14]. The process of 3D image segmentation is employed to
demarcate anatomical structures within medical scans such as magnetic
resonance imaging (MRI) or computed tomography (CT) images to form
3D digital models. Seed points were placed on the images of right and
left atria, ventricles, the ascending aorta, superior vena cava, and pul­
monary artery. “Grow from seed” automatic segmentation tool was then
applied. This tool expands the seed points to encompass regions char­
acterized by comparable Hounsfield unit (HU) intensity. The segmen­
tations subsequently underwent manual revision and refinement,
employing several tools like “Scissor”, “Paint”, “Erase”, and “Island”’ by
an experienced radiologist. A 1.5 mm thick aorta wall was constructed
using the “Hollow - Inside Surface” tool. The superior vena cava, pul­
monary artery, pulmonary vein, right atrium, and left atrium were
subjected to a wall thickness of 1 mm. The right ventricular myocardium
2.3.2. Other heart models and DNA polymerase molecule model from
existing online database
The 3D models of healthy heart, congenital heart diseases including
Tetralogy of Fallot and Transposition of the great arteries were the
creation of University Medical Center Groningen, The Netherlands [15].
The models are copyrighted under Attribution-Non-Commercial-Share
Alike 4.0 International (CC BY-NC-SA 4.0). The anterior walls of both
the right and left ventricles are incised to enable visualization of the
mitral and tricuspid valves (Fig. 6).
An intricate biomolecular model such as polymerase-DNA complex
was chosen as a test print (Fig. 6). The model was retrieved from Na­
tional Institutes of Health (NIH 3D), which serves as an open,
community-driven platform for accessing, sharing, and generating
bioscientific and medical 3D models tailored for 3D printing and inter­
active visualization, encompassing virtual and augmented reality ap­
plications [16].
Fig. 4. DAP V1 multicolor 3D printer.
Footnotes: A: Filaments are propelled by seven stepper motors, which are known as Bowden extruders, mounted on top of the printer. B: Multicolor printhead on the
left and water-soluble support material printhead on the right. Filament splitter containing ten inlets, and one outlet sits on top of the left printhead. C: Prior to each
color change, multicolor printhead moves to the blade position to trim the molten filament before retraction.
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Annals of 3D Printed Medicine 18 (2025) 100201
× 10 cm. The construction of the four models necessitated a total of 750
g of PLA, 320 g of PVA for the support structures, and 410 g of PLA for
the purging process during color alteration. Each heart is outlined with
precise anatomical characteristics (Fig. 8). Despite its stringing print,
polyvinyl alcohol does not compromise the print quality as it readily
dissolves in water. Each heart model incurs a total manufacturing cost of
30 USD, which encompasses materials, electricity, printer depreciation,
and manpower.
The second test is to evaluate the printer’s capability to produce
intricate and detailed prints, specifically those pertaining to biomole­
cular models. The resulting model showcases the precise execution of
large number of filament retractions and complex printer movements to
accurately print biopolymer chains, links, and struts between them.
Fig. 9A depicts the DNA polymerase molecule model within a watersoluble support block, whereas Fig. 9B and C illustrate the model after
the disintegration of the support structures in water, hence preserving
the integrity of the model. The total amount of PLA required for printing
the model was 53 g, with an additional 123 g allocated for purging
during color transitions, and 51 g for PVA. The printing process took a
total of 16 h to finish. The aggregate expenditure associated with the
production process, encompassing materials, electricity, printer depre­
ciation, and labor, amounts to $20 USD per biomolecular model.
Table 1
Pricing of mechanical and electrical components of DAP V1 3D printer.
Components
3030 Aluminum Extrusion
15 mm Linear Guide Rail
12 mm Lead Screw
12 mm Linear Shaft
LMK12LUU Linear Bearing
Laser-cut steel parts
GT2 Pulley 20 Teeth, 5 mm Bore
GT2 Idler Pulley 20 Teeth, 5 mm
Bore
GT2 Timing Belt
GT2 Closed Loop Timing Belt
200mm
KFL001 Pillow Block Bearing
SFH12 Shaft Support Block
Support Wheel
3030 Corner Bracket
Bolts and Nuts
Total for Mechanical components
Electronic
MKS Monster V2 Controller Board
components
MKS Pi V1.1 Board
TMC 2209 Stepper Driver
BMG Extruder Kit
Creality CR10 Hotend Assembled
MK8
NEMA 17 Stepper Motor + MKSSERVO42C-V1.0 Driver
NEMA 17 42CM04 Stepper Motor
NEMA 14 36HS2418CL16 Stepper
Motor
24 V 20A Power Supply
300 mm Aluminum Print Bed
220 V Silicone Heated Bed
SSR MOSFET for Heated Bed
Textured Glass Bed
Mechanical Endstop
Acrylic Enclosure Panels
Electrical Wire and Connectors
Total for Electric components
TOTAL
Price
(USD)
15 m
3
2
4
4
16
6
12
$ 65
$ 47
$ 16
$ 10
$8
$ 118
$3
$ 10
6m
2
$7
$3
4
8
4
30
2
1
16
8
2
$5
$8
$4
$5
$ 40
$ 349
$ 66
$ 48
$ 51
$ 44
$ 48
6
$ 66
7
2
$ 39
$ 13
2
1
1
1
1
4
1
$ 20
$ 12
$ 18
$4
$8
$1
$ 40
$ 20
$ 498
$ 847
Mechanical
components
Quantity
​
​
4. Discussion
4.1. The integration of both direct drive extruder and Bowden extruders:
hybrid extrusion
The use of either a Bowden extruder or a direct extruder is common
in conventional FDM 3D printers, though their combination is rare. The
Bowden extruder configuration involves the attachment of the extruder
to the printer frame, enabling the passage of filament through a plastic
tube known as a Bowden tube. This configuration decreases the print­
head’s weight and allows for multicolor 3D printing. However, it leads
to limited control over the filament when printing intricate and minute
features, as there is a slight variation in filament movement within the
tube. The magnitude of the filament play increases proportionally with
the length of the Bowden tube. Therefore, Bowden extruders are not
suitable for fabricating biomolecular models that require extensive fine
control over filament retractions and extrusions. In contrast, a direct
drive extruder is positioned directly above the printhead, enabling more
precise control over filament movement. However, this design increases
the printhead’s mass, thus limiting the number of direct extruders that
can be incorporated on the printhead. The increased weight of the
printhead results in decreased print speed and quality. Consequently, a
direct drive extruder is frequently employed for the purpose of printing a
single color and a single material. With direct drive extruder in “Hybrid
extrusion” system, it is possible to exert precise control over the extru­
sion and retraction of the filament within the nozzle, thereby facilitating
the printing process of an intricate DNA polymerase model. Addition­
ally, the utilization of Bowden extruders with filament splitter in
“Hybrid extrusion” system allows for smooth filament transition,
thereby enabling the printing of numerous colors (Fig. 1C).
2.4. Printing tests with our innovative multicolor DAP V1 3D printer
All digital models were imported into Orca Slicer V1.9.1 software
(SoftFever). Slicing process provides the 3D printer with exact in­
structions, known as G-code, to deposit material in order to create each
layer. Orca Slicer is open-source software that offers extensive custom­
ization for users.
Polylactic acid (Kingroon, Shenzhen Kingroon Tech Co., Kowloon,
Hong Kong) was used to print all models at a temperature of 200 ◦ C.
Polyvinyl alcohol (eSUN, Shenzhen Esun Industrial Co., Nanshan Dis­
trict, Shenzhen, China), acting as the water-soluble support material, is
printed at a temperature of 190 ◦ C. The layer height is 0.3 mm, and the
infill is 10 percent. Following this, the completed prints are immersed in
warm water at a temperature range of 40–50 ◦ Celsius, with continuous
water circulation, for a duration of 24 h, until all supporting structures
have completely disintegrated. Fig. 7 and the two videos below illustrate
the printing process of the heart models and the polymerase-DNA
complex.
4.2. Innovative DAP-Hybrid-IDEX configuration in DAP V1 multicolor 3D
printer
3. Results
In the realm of multicolor or multi-material 3D printing, there exist
two primary configurations: single nozzle and multiple nozzles.
Regarding multiple nozzle designs, there are three types of configura­
tions: IDEX (two independent extruders or printheads), fixed multiple
nozzles on a printhead, and tool changer 3D printers. Presently, the X1-C
(Bambu Lab Co., Shenzhen, China), the most sophisticated FDM printer,
employs a solitary nozzle equipped with a retract and purge system to
produce prints in a maximum of 16 colors. The device is outfitted with
advanced sensors and lightweight components, facilitating
The printing of all tests with our DAP V1 multicolor 3D printer has
been successfully completed. The first test is to evaluate the printer’s
endurance and its capacity to reproduce various macroscopic-scale
anatomical details, such as the heart. Two distinct print jobs were
used to print the four heart models. The simultaneous printing of two
models required an estimated duration of 45 h per print job. The heart
models exhibit an appropriate size, with dimensions of roughly 18 × 15
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Annals of 3D Printed Medicine 18 (2025) 100201
Fig. 5. 3D segmentation.
Footnotes: Segmentation of the heart chambers and the great vessels on CT images (A) and on 3D reconstruction (B). Segmentation of the vessel walls and heart
chambers in anterior view (C) and in posterior view (D).
Fig. 6. Test prints.
Footnotes: From left to right: Healthy heart, Tetralogy of Fallot, Transposition of the great arteries and DNA polymerase models.
exceptionally rapid printing speeds. Nevertheless, the current system
lacks the capability to incorporate a second printhead, hence impeding
the printing of PVA material in conjunction with other materials. The
ultimate goal of our research is to find an affordable and sustainable
solution to print biomedical models in multiple colors with intricate
geometry, which requires water-soluble support material. FDM tech­
nology offers the potential for printing in multiple colors and different
materials at a low cost; however, there is still a lack of an efficient and
robust system on the market that can address our needs. We successfully
combined multicolor 3D printing with single nozzle and IDEX technol­
ogy, which we call "DAP-Hybrid-IDEX” in our DAP V1 printer. Table 2
and Fig. 2 [17,18] show a direct comparison between our "DAP-Hy­
brid-IDEX" and other multiple nozzle configurations. Table 3 compares
our DAP V1 printer with the Bambu Lab X1C Combo and A1 Mini
Combo.
Of course, the DAP-Hybrid-IDEX system is not perfect in terms of
color transition duration, material waste, and the number of printable
materials. Nevertheless, we consider it the most advantageous solution
to meet our requirements. Using the DAP-Hybrid-IDEX configuration
enables simultaneous printing with two materials, eliminating the need
to purge expensive PVA during material transitions. Additionally, it
reduces the likelihood of nozzle jamming compared to concurrent
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Annals of 3D Printed Medicine 18 (2025) 100201
Fig. 7. The printing process of the heart models.
Footnotes: A: The multicolor printhead is active, B: The water-soluble support material printhead is active. The water-soluble support structures are yellowish and in
zigzag pattern.
Fig. 8. Finished test prints of heart models.
Footnotes: From left to right: Healthy heart, Tetralogy of Fallot, Transposition of the great arteries and heart failure from CT scan. A: front view, B: left side view, C:
back view.
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D.M. Lu et al.
Annals of 3D Printed Medicine 18 (2025) 100201
Fig. 9. Finished test print of DNA polymerase molecule model.
Footnotes: A: model with water-soluble support structures. B,C: model after dissolving support structures in water.
Table 2
Comparison of different FDM 3D printing with multiple nozzle configurations.
Print head
configuration
DAP-Hybrid-IDEX
IDEX
Fixed multiple nozzles on a printhead
Tools changer
Typical printer
DAP V1
Ultimaker S5
Original Prusa XL
Number of colors
Quality of color
Up to 10
May cause color bleeding due to insufficient
purging
30 s
0.09 to 0.12 g per color transition
2
Low
Higher
Sovol
SV04
2
High
Up to 4
Oozing unwanted color
Up to 6
High
10 s
No
2
Low
Higher
10 s
No
Up to 6
Low
Lower if nozzles are not calibrated
properly
Complex
Complex
Higher
Higher
Color transition time
Material for purging
Number of materials
Weight of printhead
Printing accuracy
Nozzles offset
calibration
Ease of use
Cost of maintenance
Energy consumption
Simple
Simple
Instantly
No
Up to 4
High
Lower if nozzles are not calibrated
properly
Complex
Simple
Lower
Lower
Simple
Lower
Lower
Complex
Higher
Higher
printing of PLA and PVA with the same printhead. Furthermore, DAPHybrid-IDEX enables multicolor printing, enhancing the versatility of
our printing capabilities. Since the open-source Klipper firmware allows
the connection of multiple MKS Monster 8 controller boards, the
maximum number of colors is constrained only by the number of inlets
on the filament splitter. The utilization of DAP-Hybrid-IDEX yields a
reduced number of printheads, hence diminishing the intricacy of the
printhead offset calibration procedure and the expenses associated with
the operation and upkeep of the system in comparison to a tool changer
3D printer. On the other hand, a tool changer 3D printer necessitates a
distinct printhead for every color and material. The operation of our
DAP-Hybrid-IDEX in the DAP V1 printer is more straightforward and
facilitates easier calibration of the printhead offset compared to a tool
changer 3D printer. We also incorporate closed-loop motors into the X
and Y axes, enabling the printer to autonomously correct the printhead’s
position in the event of a collision with an obstruction along its trajec­
tory, thereby minimizing layer shifts.
On a tool changer 3D printer, the procedure of adjusting the
misalignment of five printheads can be a laborious and time-intensive
task. Multiple nozzles design often lead to inaccuracies in printing.
The maintenance expenses associated with a tool changer printer are
elevated due to the increased number of mechanical components
involved. A tool changer 3D printer is typically limited to only 6 print­
heads due to insufficient space on the printer frame. Conversely, this
printer can be integrated with CoreXY kinematics, enabling extremely
fast printing. A tool changer 3D printer alters color by changing the
printheads, eliminating the need for filament purging. Each color
change occurs within just 10 s, in contrast to the minimum of 30 s
required by our DAP-Hybrid-IDEX. Our printer would require >8 h to
change filaments for a print that had 1000 color transitions. To enhance
efficiency, we can either decrease the length of the printhead or increase
the filament retraction speed. It is important to acknowledge that the
quantity of filament purging during color alterations is contingent only
upon the number of colors employed in a particular printing task and the
number of printed layers. This implies that, when considering an equal
number of layers, the quantity of purge material and the duration
required for color changes in a print job that prints many items
concurrently and a print job that prints only one object are equivalent.
Based on the aforementioned discovery, it is possible to achieve an in­
direct reduction in print time for each model by augmenting the quantity
of models produced concurrently, hence resulting in a decrease in
manufacturing costs. To achieve that, the printer must operate contin­
uously and dependably for several days. Minor faults, such as electronics
overheating, unstable voltage, loose belt drives, loose extruder screws,
or layer shifts, could cause significant damage and potentially ruin the
entire print job throughout a lengthy printing process. Hence, it is
imperative to incorporate sufficient cooling fans and an uninterruptible
power supply unit. A time-lapse camera should also be incorporated to
oversee the print work, enabling prompt intervention in the event of a
possible print failure. Additionally, it aids in the identification of error
during print job for later assessment and improvement. Lastly, akin to
aviation, 3D printers necessitate regular maintenance and a thorough
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Annals of 3D Printed Medicine 18 (2025) 100201
Table 3
A direct comparison of our DAP V1 printer with the Bambu Lab X1C Combo and the A1 Mini Combo.
Printer
General
Material and color
Motion system
Operating system
Build volume
Number of colors
Quality of color
Color transition time
Material for purging
Supported materials
Print head and nozzles
Sensors
Number of materials in a single print
Number of print head
Offset calibration between nozzles
Max speed of print head
Max acceleration of tool head
Camera
Filament Run Out Sensor
Filament Odometry
Power Loss Recover
Filament Tangle Sensor
Suitability for
Number of colors
biomedical model
Combination of multicolor and waterprinting
soluble support material printing
Print volume
Maintenance (machine components)
Pricing
DAP V1
Bambu Lab X1C combo
Bambu Lab A1 mini combo
Hybrid CoreXY
Klipper (open source)
300 × 300 × 300 mm
7 (upgradable to 10)
Acceptable
30 s
0.09 to 0.12 g per color
transition (adjustable)
PLA, PETG, TPU, PVA
CoreXY
Bambu Lab (proprietary)
256 × 256 × 256 mm
4 (upgradable to 16)
High
75 - 90 s
0.22 to 0.35 g per color transition
(adjustable)
PLA, PETG, TPU, ABS, ASA, PVA, PET, PA,
PC, Carbon/ Glass Fiber Reinforced Polymer
1
1
No
500 mm/s
20 m/s²
Up to 1080P, Timelapse supported
Cartersian
Bambu Lab (proprietary)
180 × 180 × 180 mm
4 (non-upgradable)
High
75 - 90 s
0.22 to 0.35 g per color
transition (adjustable)
PLA, PETG, TPU, PVA
2
2 (independent extruders)
Simple
200 mm/s
5 m/s²
Up to 1080P, Timelapse
supported
Yes
No
Yes
No
Sufficient
Suitable
Yes
Yes
Yes
Yes
Sufficient
Unsuitable
Sufficient
Flexible
Barely sufficient
Sourced from the manufacturer
847 USD with seven colors
Combo with four colors: 1349 USD
Plus 309 USD for each 4 colors added
1
1
No
500 mm/s
10 m/s²
Up to 1080P, Timelapse
supported
Yes
Yes
Yes
Yes
Insufficient
Unsuitable
Insufficient
Sourced from the
manufacturer
Combo with four colors:
349 USD
would decrease the cost to $20.5 USD per model, with the print job
lasting for 70 h. Similarly, printing 10 DNA polymerase models simul­
taneously would reduce the cost to $9.5 USD for each model, and the
print job would last for 69 h. Eduardo used a single color, single material
FDM 3D printer to print biomolecular models [7]. The efficacy of this
approach is limited to models of relatively modest complexity, as the
support structures necessitate manual trimming using cutting pliers.
Furthermore, manually painting the biomolecular model requires sig­
nificant labor and may not always be practical for intricate molecular
structures.
checklist before any operation in order to optimize the success of prints.
4.3. Printing quality of DAP V1 multicolor 3D printer
The four printed heart models have a uniform size, measuring around
18 × 15 × 10 cm (Fig. 8). Fig. 9 depicts a DNA polymerase molecule
model that is both visually appealing and affordable for health science
education. These models meet the need for visual and tangible aids in
biomedical education.
4.4. Economics and broader significance of our DAP V1 multicolor 3D
printer
4.5. Limitations
Our printer has several limitations. During color transitions, slight
color bleeding from the preceding color is still present. This issue can be
mitigated by increasing filament purging during each color change. For
example, the Bambu Lab printer uses three times the purging amount
compared to ours, resulting in better color quality, but this comes at the
cost of longer print times. our printer has a slower print speed due to the
heavier gantry carrying two printheads. Although the open-source
Klipper firmware offers a resonance compensation feature to cancel
machine vibrations at high print speeds, the printer itself lacks advanced
sensors that could further optimize print quality and enhance overall
performance.
As mentioned above, our focus is solely on creating colorful and
intricate biomedical models for visualization purposes in anatomy,
biology courses, or surgery planning. Producing realistic models for
medical procedures training, which require mimicking human tissue
colors and properties, is not within the scope of this study. In developing
countries, state-of-the-art printing technologies like PolyJet are often
utilized in medical education, with a printer costing over $200,000 USD.
For instance, in a study, the heart model printed with an Object 500
Connex3 PolyJet printer incurred costs exceeding $400 USD [19].
Another study employed a Stratasys J750 printer to produce a skull base
model for teaching, which cost over $1600 USD [20], making it un­
suitable for LMICs. In contrast, the cost to build our DAP V1 printer is
less than $1000 USD. For comparison, the Bambu Lab X1C costs $1658
for the 8-color upgrade version, while the A1 Mini costs $349 for the
non-upgradable 4-color printing. Neither printer includes a second
printhead for dissolvable support material. Our printer can be easily
installed in any educational facility with minimal environmental
impact. Our $30 USD heart models, despite some color bleeding, exhibit
decent surface color quality and can to a certain extent fulfill the
learning outcomes of our students. Given the same number of layers,
since the amount of material used for purging remains constant
regardless of the number of models printed at a time, we can further
reduce manufacturing costs simply by increasing the number of models
printed simultaneously. For instance, printing 4 hearts concurrently
5. Conclusions
In this study, we successfully developed and tested the DAP V1
multicolor FDM 3D printer, a novel configuration designed for produc­
ing intricate biomedical and anatomical models with multicolor and
water-soluble support material printing capability. The printed models
from various input sources demonstrate the printer’s effectiveness,
outperforming comparable FDM printers currently available on the
market.
While the print quality remains inferior to material jetting technol­
ogy, the results are sufficient for biomedical education. More impor­
tantly, our system provides significant economic advantages, with lower
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D.M. Lu et al.
Annals of 3D Printed Medicine 18 (2025) 100201
(continued )
machine acquisition and operating expenses. The DAP-Hybrid-IDEX
configuration becomes increasingly cost-efficient for larger batch pro­
duction, which is crucial in resource-limited settings.
Future optimizations in printer frame, motion system, sensors,
firmware, and software could further enhance performance, color
quality, print speed and reliability, potentially elevating the system to an
industrial-grade level. Our work presents a transformative solution to
make biomedical 3D printing accessible, affordable, and customizable
for most educational facilities. This frugal innovation facilitates wider
adoption, allowing institutions to produce learning materials on demand
and improve the quality of health science education in LMICs.
Glossary
Glossary
Abbreviation
Definition
Low and middle-income
countries
LMICs
Fused Deposition Filament
FDM
Hybrid CoreXY kinematics
​
DAP-Hybrid-IDEX
​
Independent extruders
IDEX
In 2023, low-income countries are
defined as having a gross national
income (GNI) per capita of $1145
or less, while lower-middle-income
countries have a GNI per capita
ranging from $1146 to $4515.
A 3D printing process that uses
thermoplastic filament, extruding
it layer by layer onto a build plate
to form a three-dimensional object.
A variation of the CoreXY motion
system commonly used in 3D
printers.
Our printer’s configuration
combines multicolor 3D printing
with a single nozzle and IDEX
technology
Independent extruders are a 3D
printing system where two
printheads operate separately on
the same X axis, allowing for two
materials printing, color changes,
or simultaneous production of two
objects.
The integration of both direct drive
extruder and Bowden drive
extruder.
A type of FDM 3D printer
configuration that can transition
between various printheads by
magnetic grabbing and docking
mechanism.
Vat photopolymerization is a 3D
printing process that uses light to
cure liquid photopolymer resin in a
vat, solidifying it layer by layer to
form a three-dimensional object.
Polylactic acid (PLA) is a
biodegradable thermoplastic
derived from renewable resources
like corn starch or sugarcane,
commonly used in 3D printing for
its ease of use, low melting
temperature, and eco-friendly
properties.
Polyvinyl alcohol (PVA) is a watersoluble synthetic polymer often
used in 3D printing as a support
material, allowing for easy
removal by dissolving in water
without affecting the main printed
object.
An organization established to
develop technical standards for the
manufacturing of electrical and
medical imaging equipment.
Stepper motors are electric motors
that move in precise, fixed steps,
allowing for accurate control of
position and speed, commonly
used in 3D printers and CNC
machines.
Hybrid-extrusion
​
Tool-changer 3D printers
​
Vat photopolymerization
​
Polylactic acid
PLA
Polyvinyl alcohol
PVA
National Electrical
Manufacturers
Association
NEMA
Stepper motors
​
Glossary
Abbreviation
Closed-loop stepper motors
​
DAP V1
​
ECG-gated
​
Digital Imaging and
Communications in
Medicine
DICOM
Hounsfield unit
HU
3D image segmentation
​
AttributionNonCommercialShareAlike 4.0
International
(CC BY-NC-SA
4.0)
National Institutes of Health
NIH
Definition
Closed-loop stepper motors use
feedback from sensors to monitor
and adjust their position in real
time, providing higher accuracy,
torque, and efficiency compared to
open-loop stepper systems.
The name of our constructed
version 1 3D printer
An ECG-gated CT scan is a type of
computed tomography that
synchronizes image acquisition
with the heart’s electrical activity,
reducing motion artifacts and
providing clearer images of the
heart and blood vessels.
A standard protocol for processing,
storing, and transmitting medical
images across various medical
imaging devices and systems.
A measurement scale in CT
imaging that quantifies
radiodensity, which is essential for
3D segmentation.
The process of demarcating
anatomical structures within
medical scans to form 3D digital
models.
Creative Commons license
allowing others to remix, adapt,
and build upon the work noncommercially, as long as they
credit the creator and license their
new creations under identical
terms.
The NIH 3D Print Exchange is a
platform provided by the National
Institutes of Health offering open
3D models related to biomedical
science
Declaration of competing interest
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influence
the work reported in this paper.
Declaration of generative AI and AI-assisted technologies in the writing
process
During the preparation of this work, we used ChatGPT 4 in the
writing process to improve the readability and language of the manu­
script. After using this tool, we reviewed and edited the content as
needed and took full responsibility for the content of the published
article.
Acknowledgements
We gratefully acknowledge Prof. An Le Pham and Grants and Inno­
vation Center for their invaluable support and contributions to our
study. Prof. An‘s generosity in providing both essential materials and
devices was crucial in facilitating our research efforts.
Funding sources
This research did not receive any specific grant from funding
agencies in the public, commercial, or not-for-profit sectors.
(continued on next column)
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Annals of 3D Printed Medicine 18 (2025) 100201
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