F14 - Optical Optimization of 3D-Printed Anatomical Models for Medical Education

Introduction: : Realistic, anatomically accurate 3D-printed models have emerged as powerful tools in medical education and simulation, yet many rely on opaque materials that limit their use in procedures requiring visualization of internal structures. Tissue-mimicking materials (TMMs), like those made with Stratasys’s Agilus30Clear, offer compliant mechanical behavior suitable for procedural training but suffer from poor optical clarity, which impairs visualization of subsurface anatomy. This limitation is particularly problematic for simulating interventional procedures such as percutaneous coronary intervention (PCI), where internal navigation under real-time guidance is essential [1,2]

While Stratasys recommends a silicone-based conformal coating to improve the clarity of its elastomeric prints, there is no comparative framework to evaluate the effectiveness of alternative coatings or their mechanical consequences on TMMs. Developing transparent, mechanically realistic models could greatly enhance preclinical procedural training and reduce reliance on cadavers and fluoroscopy [4,5]. Such models also support patient-specific design and rapid prototyping, particularly in cardiac and vascular simulations where internal structures are deep and difficult to visualize [3]

This study systematically evaluates five post-processing coatings for their ability to enhance transparency while preserving the mechanical fidelity of Agilus30Clear prints. We combine spectrophotometric and mechanical testing with a coronary artery model use case to explore trade-offs between optics and haptics. By establishing a reproducible framework for optical optimization, this work enables the creation of high-fidelity, transparent anatomical models for use in education, device testing, and surgical planning.

Materials and

Methods: : Samples were printed using a Stratasys J750 Digital Anatomy printer with Agilus30Clear, a flexible tissue-mimicking material. ASTM D638 Type IV dumbbell specimens (2 mm thickness) were used for mechanical testing, 50 × 32 × 1 mm rectangular sheets for optical testing, and simplified left main coronary artery (LMCA) models (4.5 mm diameter, 1 mm wall, 40 mm length) for functional demonstration. Washaway support material (SUP706B) was used on all surfaces, removed with water and spatula, then air-dried ≥ 24 hours before coating.

Five coatings were tested: silicone conformal (SC), acrylic conformal (AC), and polyurethane conformal (PC) from MG Chemicals; and oil-based (PO) and water-based (PW) polyurethane from Rust-Oleum. Samples were dip-coated (5-second submersion), drip-dried, and suspended for 72 hours at room temperature without heat or UV curing. For luminal exclusion, vessel ends were pinched to trap air during dipping.

Optical performance was evaluated using UV-Vis spectrometry at 600 nm (Avaspec-ULS-EVO-RS, n=3/group). Optical clarity was qualitatively assessed using DinoLite imaging (AM4115ZT) of printed text viewed with a 2 mm gap beneath each sample.

Mechanical testing was performed via uniaxial tension (Instron 5944, 10 mm/min, n=3/group). Parameters evaluated included stiffness at 5% and 50% elongation, ultimate tensile strength, elongation at failure, and transition stress, and were calculated using MATLAB R2023b. One-way ANOVA with Tukey post-hoc analysis were conducted using GraphPad Prism (α = 0.05).

Fracture surfaces were imaged post-failure to characterize failure modes. A PTFE-coated guidewire (0.97 mm) was advanced through SC-coated left main coronary artery (LMCA) models to evaluate procedural visibility.

Results, Conclusions, and Discussions:: All five coatings significantly improved the optical clarity of Agilus30Clear, a flexible 3D-printed TMM. Polyurethane conformal (PC) exhibited the lowest absorbance at 600 nm, indicating the greatest transparency, followed by acrylic (AC), silicone (SC), oil-based (PO), and water-based polyurethane (PW). Qualitative imaging confirmed improved text legibility through SC, AC, and PC, while PO and PW introduced yellowing and visual blur. PC remained tacky due to inadequate curing, and was eliminated early on from consideration as a viable coating (Fig.1).

Mechanically, SC and PC best preserved the elastic behavior of uncoated samples. SC produced no significant differences in stiffness or elongation at failure, and as stated PC was eliminated due to problems curing. In contrast, AC, PO, and PW significantly increased low-strain stiffness. AC increased ultimate tensile strength and exhibited adhesive failure via delamination (Fig.2). Fracture analysis showed crazing and brittle fracture in SC and PC samples, consistent with uncoated Agilus30Clear. AC samples delaminated, while PO fractured cleanly and PW showed a wavy fracture surface (Fig.3).

While each coating’s utility depends on a given application's specific requirements, SC emerged as the most balanced option offering substantial optical enhancement and minimal mechanical disruption. AC and PC offered excellent clarity but were mechanically limiting or not fully cured, respectively. PO and PW provided moderate clarity at the cost of increased stiffness.

Tissues such as skin and blood vessels demand higher mechanical compliance from coatings whereas stiffer alternatives may be considered for less compliant structures such as tendons. In LMCA models, guidewire visibility was enhanced by external SC coating and further improved by coating both internal and external surfaces. This enabled direct visualization of catheter navigation eliminating the need for fluoroscopy and allowing procedural steps to be clearly demonstrated outside of the clinic.

These findings establish a practical post-processing framework for producing transparent, elastomeric anatomical models made with varied TMMs. Such models have value in procedural training, surgical planning, and device testing, enabling direct visualization of complex anatomy and tool-tissue interactions. Future work may investigate multilayered structures and anisotropic materials to extend the applicability of transparent TMMs across a wider range of clinical simulations.

Acknowledgements and/or References (Optional):: Works Cited
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