Abstract
Background
Team Bath Heart are developing a Total Artificial Heart which uses compression of artificial ventricles to pump blood. Early testing of the ventricles highlighted issues: polymer viscosity increase during pre-curing caused air bubbles; misalignment of the wax mandrel, caused non-uniform thickness; potential leeching of chemical components.
Methods
Gravity casting, was used to make ventricles with thermoset polymer (polyol and isocyanate as catalyst). A reusable casting wax mandrel enabled the thin-walled structure to be made in an FDM-printed ABS female mould (fig 1a). The material selected was Polyurethane rubber for its flexibility, high tensile strength, and biocompatibility. PU30 and PU60 rubbers were used as the materials for the functional models.
The air bubbles were analysed with a VHX microscope. Samples of the sacs were tensile tested under uniaxial load with Instron 5965. Model stress-strain curves were fitted with the Mooney-Rivlin model, suitable for the hyperelastic materials. Chemical leeching was analysed by placing samples in saline and measuring absorbance spectra from the saline.
Results
The obtained images and measurements show that the PU60 provides a better surface finish with a smaller size, density, and depth of the air gaps (fig 1b). The harder PU60 featured better
properties: tensile strength = 2.29 MPa; elongation at break = 240%; and Young Modulus = 2.77 MPa.
These values were smaller than textbook values: for the thin structures, manufacturing imperfections significantly affect load capacity.
Absorbance spectra changed over 10 hours with a growth in the peak at XXX nm.
Conclusion
The process is sufficient to repetitively make a watertight sac model for basic testing. However, further improvements are crucial to achieve biocompatibility of the artificial ventricles.
Future work on the system includes improvements in the manufacturing process. The moulding procedure shall be more standardised including better controlled environment and in-process de-airing, eliminating the defects in the polymer. Moreover, additional cleaning steps shall be added for the sac interior to prevent blood contamination.
In addition, alternative manufacturing methods will be analysed. For example, SLA printing was initially tested in terms of quality before post-processing.
Team Bath Heart are developing a Total Artificial Heart which uses compression of artificial ventricles to pump blood. Early testing of the ventricles highlighted issues: polymer viscosity increase during pre-curing caused air bubbles; misalignment of the wax mandrel, caused non-uniform thickness; potential leeching of chemical components.
Methods
Gravity casting, was used to make ventricles with thermoset polymer (polyol and isocyanate as catalyst). A reusable casting wax mandrel enabled the thin-walled structure to be made in an FDM-printed ABS female mould (fig 1a). The material selected was Polyurethane rubber for its flexibility, high tensile strength, and biocompatibility. PU30 and PU60 rubbers were used as the materials for the functional models.
The air bubbles were analysed with a VHX microscope. Samples of the sacs were tensile tested under uniaxial load with Instron 5965. Model stress-strain curves were fitted with the Mooney-Rivlin model, suitable for the hyperelastic materials. Chemical leeching was analysed by placing samples in saline and measuring absorbance spectra from the saline.
Results
The obtained images and measurements show that the PU60 provides a better surface finish with a smaller size, density, and depth of the air gaps (fig 1b). The harder PU60 featured better
properties: tensile strength = 2.29 MPa; elongation at break = 240%; and Young Modulus = 2.77 MPa.
These values were smaller than textbook values: for the thin structures, manufacturing imperfections significantly affect load capacity.
Absorbance spectra changed over 10 hours with a growth in the peak at XXX nm.
Conclusion
The process is sufficient to repetitively make a watertight sac model for basic testing. However, further improvements are crucial to achieve biocompatibility of the artificial ventricles.
Future work on the system includes improvements in the manufacturing process. The moulding procedure shall be more standardised including better controlled environment and in-process de-airing, eliminating the defects in the polymer. Moreover, additional cleaning steps shall be added for the sac interior to prevent blood contamination.
In addition, alternative manufacturing methods will be analysed. For example, SLA printing was initially tested in terms of quality before post-processing.
| Original language | English |
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| Publication status | Published - 13 Nov 2024 |
| Event | 30th Congress of the International Society for Mechanical Circulatory Support (ISMCS) - Light Cube, Utsunomiya, Japan Duration: 13 Nov 2024 → 15 Nov 2024 https://kinki-convention.jp/ismcs30/ |
Conference
| Conference | 30th Congress of the International Society for Mechanical Circulatory Support (ISMCS) |
|---|---|
| Country/Territory | Japan |
| City | Utsunomiya |
| Period | 13/11/24 → 15/11/24 |
| Internet address |