Design and Performance Evaluation of TPMS-Based Dual-Layer Gradient Porous Structures for Bone Scaffolds.

Area of Science:

• Biomaterials Engineering
• Orthopedic Implants
• Porous Structure Design

Background:

• Bone tissue engineering requires scaffolds with optimized mechanical and permeability properties.
• Triply Periodic Minimal Surface (TPMS) structures offer tunable porosity and mechanical responses.
• Gradient porosity in scaffolds can mimic bone's heterogeneous nature, improving integration.

Purpose of the Study:

• To investigate and compare the properties of various P-type TPMS porous structures for bone scaffold applications.
• To evaluate the influence of dual-layer gradient designs (axial vs. radial) on mechanical and permeability performance.
• To identify optimal porosity distributions within dual-layer gradient TPMS scaffolds for enhanced bone implant functionality.

Main Methods:

• Development of six homogeneous, axial, and radial single/dual-layer TPMS structures with consistent average porosity.
• Selection and further design of dual-layer gradient structures based on initial property comparisons.
• Mechanical and permeability testing of ten axial and radial dual-layer gradient TPMS structures with varied inner/outer layer porosities.

Main Results:

• Dual-layer gradient structures exhibited more bone-like pore/stress distributions, reduced maximum stress, and higher yield strength.
• Radial dual-layer gradient structures demonstrated superior yield strength (112.75-139.97 MPa), elastic modulus (11.15-13.01 GPa), and permeability (1.51-10.01 × 10^-9 m²) compared to axial designs.
• A radial dual-layer structure with 27.5% inner layer porosity and 42.5% outer layer porosity showed the best overall performance.

Conclusions:

• Dual-layer gradient TPMS scaffolds, particularly radial designs, offer significant advantages for bone scaffold applications.
• Porosity distribution is critical; lower inner and higher outer porosity enhance mechanical and permeability properties.
• Findings provide direct guidance for designing customized bone implants with tailored performance characteristics.