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The effect of porosity on the mechanical properties of 3D-printed triply periodic minimal surface (TPMS) bioscaffold

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Abstract

Prevailing tissue degeneration caused by musculoskeletal maladies poses a great demand on bioscaffolds, which are artificial, biocompatible structures implanted into human bodies with appropriate mechanical properties. Recent advances in additive manufacturing, i.e., 3D printing, facilitated the fabrication of bioscaffolds with unprecedented geometrical complexity and size flexibility and allowed for the fabrication of topologies that would not have been achieved otherwise. In our work, we explored the effect of porosity on the mechanical properties of a periodic cellular structure. The structure was derived from the mathematically created triply periodic minimal surface (TPMS), namely the Sheet-Diamond topology. First, we employed a series of software including MathMod, Meshmixer, Netfabb and Cura to design the model. Then, we utilized additive manufacturing technology to fabricate the cellular structures with designated scale. Finally, we performed compressive testing to deduce the mechanical properties of each cellular structure. Results showed that, in comparison with the high-porosity group, the yield strength of the low-porosity group was 3 times higher, and the modulus was 2.5 times larger. Our experiments revealed a specific relationship between porosity and Young’s modulus of PLA-made Sheet-Diamond TPMS structure. Moreover, it was observed that the high- and low-porosity structures failed through distinctive mechanisms, with the former breaking down via buckling and the latter via micro-fracturing.

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Authors

Corresponding author

Correspondence to Zizhen Cai.

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Conflict of interest

The authors declare that there is no conflict of interest.

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This study does not contain any studies with human or animal subjects performed by any of the authors.

Appendix

Appendix

Detailed information about PLA used during the printing process is presented below:

 

Polylactic acid (PLA)

Density

1.00–2.47 g/cc

Additive loading

10.0–40.0%

Tensile strength, ultimate

14.0–114 MPa

Tensile strength, yield

2.00–103 MPa

Modulus of elasticity

0.0850–13.8 GPa

Melting point

90.0–180 °C

Maximum service temperature, air

60.0–240 °C

Processing temperature

190–220 °C

Nozzle temperature

150–235 °C

 

Ultimaker 2

Print technology

Fused filament fabrication (FFF)

Maximum power output

221 W

Layer resolution

0.25 mm nozzle: 150–60 micron

0.4 mm nozzle: 200–20 micron

0.6 mm nozzle: 400–20 micron

0.8 mm nozzle: 600–20 micron

XYZ resolution

12.5, 12.5, 5 micron

Feeder type

Geared feeder

Display

Dot-matrix display with click wheel

Print head

Swappable nozzle

Nozzle diameters

0.25, 0.4, 0.6, 0.8 mm (all included)

Build speed

< 24 mm3/s

Nozzle temperature

180–260 °C

Nozzle heat-up time

< 2 min

Build plate leveling

Assisted leveling

Build plate

20–100 °C heated glass build plate

Operating ambient temperature

15–32 °C (59–90 °F)

Original load versus deformation curves and stress–strain curves of all samples are listed below:

figure afigure a

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Cai, Z., Liu, Z., Hu, X. et al. The effect of porosity on the mechanical properties of 3D-printed triply periodic minimal surface (TPMS) bioscaffold. Bio-des. Manuf. 2, 242–255 (2019). https://doi.org/10.1007/s42242-019-00054-7

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  • DOI: https://doi.org/10.1007/s42242-019-00054-7

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