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Study Confirms
3D Printed Tissue
Can Mimic theProperties ofPorcine Liver,Epicardium andAorta Tissue2Introduction

Anatomical 3D printing has mainly been used fortraining, education and surgical planning purposes
because previous materials have been unable to mimic
the mechanical and material properties of tissue.
However, there are new Digital Anatomy (DA) materials
on the market that mimic the material configurationsof soft organ, subcutaneous tissue and myocardium.
These new DA materials, developed by Stratasys,promise to mimic the mechanical performance of
biological tissue and allow for lower cost and quicker
development of models.

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The use of 3D anatomical models promise to bebeneficial because it doesn’t require regulatory ethicalrequirements (or a facility to handle the biohazards
and sterilization) and offers longevity and reduced costcompared to ex-vivo and in-vivo cadaveric animaltesting. In addition, 3D technologies also address
constraints of conventional manufacturing that require
fabrication processes like molding and casting, which
is not ideal for the creation of patient-specific models
because of high tooling costs and process time.

3Study Confirms
3D Printed
TissueCan Mimic theProperties ofPorcine Liver,
Epicardium
and Aorta
TissueObjectiveMethods

The study focused on comparing porcine tissue
with the mechanical properties of DA Soft Organ(SO), the lubricity of DA myocardium (very stiff,extremely stiff and highly contractile) and the tactile
capabilities of DA Subcutaneous Tissue (ST).

The stiffness and lubricity of 3D models wascompared to those of porcine tissue. To mimic theconditions during in-vivo procedures, tests weredeveloped to evaluate lubricity/friction, qualitative
cutting, stiffness and puncture testing andtunneling (subcutaneous tissue) for comparison
between porcine tissue and DA materials.

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Scientists and engineers from Medtronic, a global
leader in medical device manufacturing, conducted
an independent third-party comparison of theDA materials to porcine tissue. The following
summarizes the findings and presents implications
for future work in material development.

The mechanical properties of porcine tissue (liver,aorta and epicardium) were compared to thosefrom a wide spectrum of 3D DA material blends.
Porcine tissue was chosen as the baseline forcomparison because of its similarity to humantissue, availability, and the precedent for its use in
pre-clinical testing. All samples were printed on theStratasys J750 Digital Anatomy™ 3D printer.

4Key findings
Stiffness Testing

Success:

Porcine livers were dissected and assessed forstiffness from 1 to 3 N. From those samples, two
representative values for thickness were usedas the size for the DA liver cube samples. Two
iterations of the porcine and DA liver configurations
were tested.

•The experimental DA SO liver configurations
have the capability to match the stiffness ofliver tissue.

•The stiffness of 3D printed parts is moreconsistent than porcine tissue, which can behighly variable between samples.

The statistics for Iteration 1 – Liver 2 are displayedin Table 1, which shows the lower standard
deviation, which equates to higher repeatabilityof DA SO liver in comparison to the porcine livertissue.
Sample Type

Mean [N/mm]

Standard
Deviation

Standard Error ofthe Mean (SEM)

Iteration 1 – Liver 2

0.695

0.025

0.010

0.570

0.033

0.014

0.914

0.020

0.008

0.743

0.033

0.003

1.144

0.455

0.038

Shell: 0.4 mm | Thickness: 15 mm
Iteration 1 – Liver 2
Shell: 0.4 mm | Thickness: 25 mm
Iteration 1 – Liver 2White Paper

Shell: 1.0 mm | Thickness: 15 mm
Iteration 1 – Liver 2
Shell: 1.0 mm | Thickness: 25 mm
Porcine Liver Tissue
Table 1

5Key findings

Lubricity (epicardium and aorta)
Porcine heart tissue samples were attached
to a tribometer and tested with a 0.25 indiameter steel ball with an applied axial
force along the tissue surface of 0.75 N
at a velocity of 0.5 mm/s for a distance of30 mm. The output was a coefficient offriction vs. time curve which was analyzed
for a stabilized window of time. DA
myocardium was also attached to the baseof the tribometer and tested with a 0.25 indiameter steel ball probe with the following
lubricant conditions: none (dry), DI water,
mineral oil, and dish soap.
All of the DA printed materials were closein value to the porcine aorta when tested
with a lubricant layer of soap, with Agilus
being slightly higher in value than the DA
materials. DA myocardium had values which
encompassed the lower to upper quartile ofthe porcine epicardium and Agilus was very
close to porcine epicardium under these
conditions.

Figure 1

Figures 1-5 shows how the various printed
configurations compare with the porcine
tissue values.
Success:White Paper•

By combining the ability to modify thecoefficient friction with tissue realistic
values, DA materials can allow for more
appropriate bench testing boundary
conditions prior to utilizing animal or
cadaver models.

Figure 26Tunneling and Puncture (Subcutaneous)
Cutting, puncture and tunneling of DA ST(fat and muscle) were evaluated qualitatively
by pre-clinical implant specialists. They
found the puncture and tunneling to beclose to real tissue behavior for many of theDA ST configurations, however, cutting wasnot. According to the specialists, too muchforce was needed to create an initial incisionand there was also too much drag in the
cutting motion.
Success:•DA materials can be used to design
anatomical models for qualitative
benchtop testing, implant procedure
testing and planning because of its
ability to mimic mechanical properties
and the qualitative hepatics of tissue.

Figure 3

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Figure 4Figure 5

7Summary

In summary, the new DA materials developed byStratasys mimic the mechanical performance of biologicaltissue including soft organs, subcutaneous tissue andmyocardium. Results from this study showed:•DA SO liver configurations displayed the capability
to match the stiffness of liver tissue and were moreconsistent between samples.

•The lubricity of DA materials with surface treatments
were similar to porcine epicardium and aorta.

•Puncture and tunneling of DA materials also behaved
comparable to real tissue, however, qualitative cutting
had limited performance.

Despite a few shortcomings, the DA materials fromStratasys perform more like real tissue than any othercommercial 3D printed materials on the market today.
These promising results suggest that in addition to being atool for surgery, training and education, anatomical models
made with DA materials can add new value as a researchtool and could reduce preliminary animal testing and usageof cadaver models.
Read the full study results here: PolyJet 3D Printingof Tissue Mimicking Materials: An Investigation ofCharacteristic Properties of 3D Printed Synthetic TissueLearn more about Digital Anatomy™ Material

Questions? Contact Medical@Stratasys.com

Stratasys Headquarters

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7665 Commerce Way,
Eden Prairie, MN 55344+1 800 801 6491 (US Toll Free)+1 952 937-3000 (Intl)+1 952 937-0070 (Fax)

1 Holtzman St., Science Park,PO Box 2496
Rehovot 76124, Israel+972 74 745 4000
+972 74 745 5000 (Fax)stratasys.com
ISO 9001:2015 Certified© 2021 Stratasys. All rights reserved. Stratasys, the Stratasys Signet logo is a registered trademark of Stratasys Inc. PolyJet,
J750 Digital Anatomy and Agilus are trademarks of Stratasys, Inc. All other trademarks are the property of their respective
owners, and Stratasys assumes no responsibility with regard to the selection, performance, or use of these non-Stratasys
products. Product specifications subject to change without notice. WP_PJ_Anatomical 3D printing_0221a

White Paper

Creating
biomechanicallyaccuratebone models.

2Creating biomechanicallyaccurate bone models.
To create realistic synthetic musculoskeletal
models for medical device development,
physician training, surgical demonstration andprocedural planning, synthetic bones must
replicate the density properties and mechanicalbehavior of human bone.

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The J750 Digital Anatomy™ printer gives
clinicians and engineers the power to create
the most lifelike anatomical models available.
Combinations of unique materials that vary insoftness, flexibility and density, and more than
100 clinically-validated preset anatomy options,help to mimic human bone like never before.

3THE POWER TO CREATE

Accurate cortical and cancellous bones:
Testing screw pull out force and driving torqueIn 2020, researchers at the Computational
Mechanics and Experimental Biomechanics Lab
evaluated the characteristics of bone models 3D
printed on the J750 Digital Anatomy printer andhow accurately they replicate screw pull out force
and driving torque.
Method3D printed models of cortical and cancellous
bone were created using Digital Anatomy printersoftware. Pilot holes were drilled into each model,
and tapped with the appropriate tap. The mostcommonly-used cortical and cancellous screws
were inserted to the ASTM standard depth fortesting bone substitutes.
Pullout tests were performed until the screw wasreleased from the bone model, and measured tocompare force and displacement. Driving torqueand pullout measurements were then compared tovalues found in literature and to ASTM standards.
Results
Screw pull out force during screw insertion
corresponded to those found in literature for thecortex of a cadaver bone, demonstrating that the3D printed model accurately replicates cortexthickness.
Conclusion

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Orthopedic screws have a similar haptic response
in human bone and 3D printed bone models.
The J750 Digital Anatomy printer allows cliniciansand engineers to control density properties ofbone models with physician-tested anatomicalpresets. 3D printed models accurately mimic bonedensity characteristics and behave like native bonewhen force is applied such as drilling, reaming, orsawing.

4THE POWER TO CREATE

Accurate lumbar spine models:Testing mechanical performance
In 2020, researchers from the Technion Instituteof Technology Materials Science and Engineering
Laboratory performed mechanical lab tests tomeasure the mechanical accuracy of 3D printed
synthetic spine models compared to cadaverspine.
MethodUsing Digital Anatomy printer software, researchers
constructed four lumbar spine models using
3D printed lumbar vertebrae (S1-L3), ligaments,
sacrum, facet joints, and intervertebral discs. Eachmodel was created using unique pre-set material
combinations that varied in flexibility, stiffness anddensity to mimic a range of native musculoskeletal
characteristics.
Mechanical tests were performed to simulate thenatural axes of movement of the human spine
as force is applied: disc compression, extension,flexion, lateral bending, and axial tension. Forcevalues were then compared to those found inliterature for human cadaver lumbar spines.
Results
Mechanical disc compression, displacement,and elasticity values for the 3D printed modelcorresponded to those found in literature forcadaver lumbar spines, demonstrating thatthe synthetic model accurately replicatesbiomechanical behavior of human bone.
Conclusion

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3D printed L3-S1 models accurately represent therange of motion of human and cadaver spines.
Digital Anatomy printer technology uniquely allows
clinicians and engineers to control the range oflumbar disc stiffness to accurately mimic thedisease pathologies and anatomy variations of thehuman spine.

5

Unlock the power to mimic
native bone structures.
• Highly-realistic, low-risk training• High repeatability between samples• Clinically-relevant benchtop testing• Most consistent, accurate representation of bone
• Cost reduction of up to 70%

Learn more about theJ750 Digital Anatomy
printer, materials andsoftware at Stratasys.com.
Questions? Contact us atmedical@stratasys.com.
References
Dahan, Gal et al., “Screw Pull-Out and Driving Torque Experiments,” Computational Mechanics and Experimental Biomechanics Lab, Final Report(2020).
ASTM F1839 – 08, Standard Specification for Rigid Polyurethane Foam for Use as a Standard Material for Testing Orthopaedic Devices andInstruments, ASTM International, West Conshohocken, PA, USA, (2016).
Barak, Yaron, “Biomechanical Evaluation of a Printed Digital Anatomy Lumbar (L3-S1 Spine Model), Technion Institute of Technology Materials
Science and Engineering Laboratory, Final Report (2020).

Stratasys Headquarters

White Paper

7665 Commerce Way,
Eden Prairie, MN 55344+1 800 801 6491 (US Toll Free)+1 952 937-3000 (Intl)+1 952 937-0070 (Fax)

1 Holtzman St., Science Park,PO Box 2496
Rehovot 76124, Israel+972 74 745 4000
+972 74 745 5000 (Fax)stratasys.com
ISO 9001:2015 Certified© 2020 Stratasys. All rights reserved. Stratasys, Stratasys signet, J720 and Digital Anatomy are trademarks of Stratasys Ltd. and/or its
subsidiaries or affiliates and may be registered in certain jurisdictions. All other trademarks belong to their respective owners.
WP_PJ_BoneDataOverview_1120a

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BiomechanicalTests Confirm thePotential for 3D
Printing Suturable
Vascular Models with
the Stratasys DigitalAnatomy Printer2

Biomechanical Tests Confirm thePotential for 3D Printing Suturable
Vascular Models with the Stratasys
Digital Anatomy™ PrinterTo create the most realistic, patient-specific simulation forsurgical training, vascular models must mimic how native
tissue responds to pressure, punctures, and stitches.
Experiencing the behavior of biological blood vessels during
anastomosis is a crucial part of preparing surgeons totreat patients safely and confidently, and materials must be
chosen carefully to produce the most accurate anatomicalmodels.
In 2021, researchers at the University of Pavia in Pavia, Italy evaluated the performance of blood vessel
models printed on the Digital Anatomy Printer, comparing different material combinations to porcine tissue
samples. Their research resulted in a new printing preset for suturable vascular models that mimics vessels’
mechanical response during suturing.
MethodWhite Paper

In order to create the material mixture for blood vessel suturability, the researchers printed 37 different
presets. Mechanical tests were performed to validate the compliance of the 3D printed models comparedto fresh porcine tissue samples including single stich, puncture, tensile and suturing. The single stitch
test is shown in Figure 1 and the tensile test is shown in Figure 2. Researchers thoroughly tested these
combinations by performing 10 repetitions for each material and mechanical test type. Of the 37 samples,
6 showed the most accurate results compared to the real porcine tissue.

3

Figure 1: Comparison between single stitch mechanical tests performed on porcine aorta (up) and on a 3DP material (down).

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Figure 2: Uniaxial tensile test performed on a 3D printed sample sutured by an expert surgeon in order to mimic the surgical suture ona medium caliper arterial vessel.

4The Results
The following table (Figure 3) presents the selected material in comparison to porcine tissue in the different
tests – puncture and single stich.

Figure 3: Overall results of puncture and single stich tests on the pool of 6 selected materials compared with porcine aorta
tracts (namely aortic arch, thoracic aorta and abdominal aorta)

Figure 4: load-time curves acquired during puncture tests:
Comparison between 3DP materials and different porcine aorta
tracts on one representative curve per material (not normalized)

Table 1: Normalized puncture tests’ results: comparison between
3DP materials and different porcine aorta tracts

Figure 4 above represents the load-time curves, in which values are not normalized according to thesample thickness. Table 1 shows the normalized values for the same test.
The values measured demonstrate repeatable results between the 3D printed models, while in the tissue
samples, the standard deviation is much higher. The selected presets accurately resemble the measured
values from the porcine vessels.

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Two material combinations were identified as the most promising solutions for simulating and practicing
surgical techniques on blood vessels. These materials could simulate the flexibility and softness of bothminor and thicker vessels.

5The Conclusion
Suturable vessel wall 3D models printed with the Stratasys Digital Anatomy Printer can provide surgeons
and researchers biomechanically accurate blood vessel models for realistic treatment planning and training.
Stratasys developed new software presets based on this research allowing clinicians to control the rangeof thickness and flexibility to mimic disease states and variations of human blood vessels on medical 3D
printed models.

Unlock the power to simulate suturable blood vessels.
lHighly-realistic, low-risk training

lHigh repeatability between sampleslPhysiological response of native vascular tissuelStandardize surgical skills and delivery of carel

Tested material combinations create realistic models

View the complete study findings at the following link: Quantitative Assessment of 3D Printed Blood
Vessels Produced with J750™ Digital Anatomy™ for Suture Simulation

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Learn more about the Digital Anatomy™ Printer, materials and software at https://www.stratasys.com/3dprinters/j750-digital-anatomy.

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