The study examined thermoplastic polyurethane, or TPU, and styrene-ethylene-butylene-styrene, or SEBS, both flexible thermoplastics considered for polymeric heart-valve research. Synthetic leaflets may avoid the calcification and structural degeneration associated with biological tissue valves while eliminating the lifelong anticoagulation required by mechanical valves, while additive manufacturing permits complex or patient-specific geometries. The investigators used commercially available filaments with a diameter of 1.75 ± 0.05 millimetres and printed the dog-bone specimens with a 0.4-millimetre nozzle, varying filament alignment among axial, transverse and diagonal orientations. Eight specimens were produced per polymer for each alignment, yielding 24 dog-bone specimens per polymer across the three orientations. Six printed three-leaflet valve geometries were produced for each material.

Tensile tests at crosshead speeds of 50, 100 and 500 millimetres per minute revealed a rate-dependent response. TPU reached its highest stress and strain values at 100 millimetres per minute regardless of filament alignment, while slightly lower results occurred at 50 millimetres per minute. SEBS displayed a different pattern, showing high resistance to fracture at 500 millimetres per minute. In a direct comparison at 50 millimetres per minute with axial alignment, maximum stresses differed by only 4%, whereas the strain difference reached 90%. The researchers therefore characterized TPU as the more ductile material. They subsequently used 100 millimetres per minute for the main tensile comparison and derived elastic modulus, yield strength, maximum stress, strain at maximum stress and maximum plastic strain from the measurements.

Digital image correlation showed that the printed structures were strongly anisotropic: their mechanical properties depended on the direction in which the filament had been deposited relative to the applied load. In tension, axial alignment produced the highest Young’s modulus for both polymers, while transverse alignment produced the lowest. TPU recorded moduli of 28.49 ± 2.83 megapascals for axial prints, 22.50 ± 2.15 MPa for transverse prints and 24.04 ± 2.31 MPa for diagonal prints. Corresponding SEBS values were 174.71 ± 17.06, 97.34 ± 9.42 and 105.15 ± 10.33 MPa. The average tensile modulus of SEBS was more than five times that of TPU. This directional dependence is a central complication in layer-by-layer manufacturing, because the mechanical behavior of a printed component can vary with the relationship between its toolpaths and the loads it experiences.

The optical strain maps also showed where deformation developed before fracture. Immediately before rupture, the maximum principal strain exceeded 0.60 in axially printed TPU, compared with more than 0.35 in axially printed SEBS. TPU therefore accommodated substantially larger deformation before breaking, while SEBS developed narrow zones of localized strain. Transverse prints produced the most heterogeneous fields in both materials, with multiple localization zones and concentrations near specimen edges. Axial alignment created the sharpest necking zones, and diagonal alignment distributed localized deformation over a broader area. Across the three configurations, maximum principal strain in TPU was approximately 40% to 70% greater than in SEBS, providing spatial evidence for the polymers’ contrasting tensile behavior.

Compression produced the same broad material ranking but different numerical values. Cuboid specimens were compressed between parallel plates at 1 millimetre per minute. SEBS again had the higher modulus in every orientation, exceeding TPU by more than three times on average. Axial TPU had a compressive modulus of 16.62 ± 1.59 MPa, compared with 60.08 ± 5.72 MPa for SEBS. Transverse and diagonal values were 11.70 ± 1.14 and 12.11 ± 1.1 MPa for TPU, and 39.51 ± 3.85 and 43.87 ± 4.21 MPa for SEBS. The difference between the materials in maximum compressive stress was approximately 70%, while alignment had comparatively little influence on maximum stress. For SEBS, however, the spread in final force across printed specimens was much greater than for TPU, indicating less consistent mechanical behavior among specimens.

When complete three-leaflet valve geometries were compressed at 30 millimetres per minute, SEBS resisted deformation more strongly and its force-displacement curve was steeper. TPU compressed with less initial resistance, consistent with its greater compliance. The final-force spread was 0.09 newton for TPU, equal to 4% of the maximum case, compared with 2.66 newton for SEBS, or 20% of its maximum. Digital image correlation recorded a maximum vertical displacement of 4.2 millimetres in the TPU leaflets after 50 seconds. The corresponding SEBS value was 4.1 millimetres, but the deformation patterns differed: the TPU lateral leaflets converged and the gap between them disappeared, whereas the SEBS leaflets retained a gap and showed small movements at the commissures where the leaflet edges meet.

The researchers converted the tensile data into Mooney–Rivlin hyperelastic material models for finite-element analysis. A five-parameter model was used for TPU, while SEBS was represented with a two-parameter model. The final simulation used quadratic tetrahedral elements, with 80,840 elements and 218,078 nodes; a convergence analysis found less than 2% difference in stress, strain and displacement between two neighboring meshes. The numerical TPU model differed from the experimental displacement field by 5%, while the reported discrepancy for SEBS was 10%. The simulations also identified a maximum equivalent stress of 82.8 MPa in SEBS, approximately 20 times the value calculated for TPU. Stress localization near leaflet attachment points was identified as an area for additional fatigue research, rather than as evidence that failure would occur in a functioning valve.

The results place the two polymers on different sides of a design trade-off relevant to future polymeric TAVI prostheses. TPU’s lower stiffness and greater elongation may suit leaflets intended to be highly compliant, whereas SEBS may be advantageous where rigidity is desired. TPU’s compressive modulus fell within the approximately 10–30 MPa range reported for native aortic valve tissue, while SEBS was stiffer than that tissue; both were more compliant than glutaraldehyde-fixed bovine pericardium. These are mechanical comparisons rather than demonstrations of superior valve performance. The specimens were tested quasi-statically at room temperature, whereas valve leaflets operate at 37°C under repeated pulsatile pressure and flow. The researchers also did not evaluate sterilization, long-term hemocompatibility, platelet adhesion, thrombus formation or the effects of print-surface roughness and residual processing aids.

Accordingly, the work supports TPU and SEBS as candidates for further investigation rather than as clinically validated valve materials. The researchers identified several required next steps: physiologically relevant fatigue testing, dynamic mechanical analysis, biocompatibility and hemocompatibility assessment, sterilization studies and constitutive models that capture the anisotropy and rate dependence created by printing. A complete device would also need hydrodynamic performance testing and assessment of leaflet coaptation, prolapse and durability through repeated opening and closing cycles. The central result is not a finished replacement valve but a demonstration that changing filament direction can substantially alter a printed structure’s mechanical response, while switching from TPU to SEBS can increase stiffness several-fold. Those measured effects provide a foundation for engineering and simulating patient-specific polymeric TAVI devices, but substantial device-level testing remains before any clinical application.

Subject of Research: Mechanical characterization of 3D-printed TPU and SEBS leaflets for polymeric TAVI prostheses

Article Title: Experimental study of TPU and SEBS additively manufactured leaflets for novel aortic valve polymer TAVI prosthesis

Article References: Kuchumov, A. G., Khoroshev, D., Kutuzova, A., Baranov, A., Krestyaninov, O., Barbashina, E., Zelenchuk, P., Matjeka, E., Pandelani, T., & Nemavhola, F. (2026). Experimental study of TPU and SEBS additively manufactured leaflets for novel aortic valve polymer TAVI prosthesis. Frontiers in Bioengineering and Biotechnology, 14, Article 1959014. https://doi.org/10.3389/fbioe.2026.1959014

Image Credits: AI Generated

DOI: 10.3389/fbioe.2026.1959014

Keywords: polymeric TAVI, 3D-printed heart valves, thermoplastic polyurethane, SEBS, aortic valve leaflets, additive manufacturing, digital image correlation, hyperelastic materials, finite-element simulation, Experimental, additively, manufactured