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<p>The development of low-cost, patient-specific orthopedic implants with bioactive surfaces remains challenging for resorbable polymers such as polylactic acid (PLA), due to limited thermal stability and poor coating adhesion. This study evaluates a novel powder bed annealing process that simultaneously enhances the mechanical and thermal performance of FFF-printed PLA while forming a bioactive hydroxyapatite (HA) or HA/titanium dioxide (TiO₂) coating. PLA specimens fabricated by fused filament fabrication (FFF) were annealed at 170–190&#xa0;°C in HA or HA/TiO₂ powder beds, followed by autoclave sterilization under different drying conditions. Two-factorial experimental designs were applied to assess mechanical behavior, thermal stability, coating thickness, chemical composition, and coating adhesion. Annealing temperature was identified as the dominant parameter. Samples treated at 180&#xa0;°C showed the highest flexural strength (up to 37&#xa0;MPa) and elastic modulus, with autoclaving, particularly with drying, maintaining or further improving these properties. Impact resistance increased by over 100% after sterilization for selected conditions. Powder bed annealing increased the Heat Deflection Temperature from ~ 65&#xa0;°C for as-printed PLA to ≥ 150&#xa0;°C, enabling deformation-free autoclave sterilization. Bioactive coatings with thicknesses of 20–50&#xa0;μm remained stable after sterilization, especially for samples annealed at 180&#xa0;°C. EDS analysis confirmed deep HA particle diffusion into the polymer matrix. Coating adhesion strengths between 83 and 139&#xa0;MPa exceeded values commonly reported for polymer–ceramic systems and resisted bending stresses up to 91&#xa0;MPa. These results demonstrate that powder bed annealing is a single-step, scalable process capable of integrating mechanical reinforcement, thermal stabilization, and osseointegrative surface formation, offering a practical manufacturing route for customized, sterilization-resistant PLA implants.</p>

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Adhesion, sterilization resistance and heat deflection temperature of 3D printed PLA parts coated with hydroxyapatite by powder bed annealing

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年7月21日

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  • Felipe dos Anjos Rodrigues Campos,
  • Thiago de Oliveira Santos,
  • Kauã Ferreira de Almeida,
  • João Victor Rezende Amaro,
  • Pedro Henrique Veiga Oliveira,
  • Letícia de Souza Castro Filice,
  • Leonardo Rosa Ribeiro da Silva,
  • Álisson Rocha Machado

摘要

The development of low-cost, patient-specific orthopedic implants with bioactive surfaces remains challenging for resorbable polymers such as polylactic acid (PLA), due to limited thermal stability and poor coating adhesion. This study evaluates a novel powder bed annealing process that simultaneously enhances the mechanical and thermal performance of FFF-printed PLA while forming a bioactive hydroxyapatite (HA) or HA/titanium dioxide (TiO₂) coating. PLA specimens fabricated by fused filament fabrication (FFF) were annealed at 170–190 °C in HA or HA/TiO₂ powder beds, followed by autoclave sterilization under different drying conditions. Two-factorial experimental designs were applied to assess mechanical behavior, thermal stability, coating thickness, chemical composition, and coating adhesion. Annealing temperature was identified as the dominant parameter. Samples treated at 180 °C showed the highest flexural strength (up to 37 MPa) and elastic modulus, with autoclaving, particularly with drying, maintaining or further improving these properties. Impact resistance increased by over 100% after sterilization for selected conditions. Powder bed annealing increased the Heat Deflection Temperature from ~ 65 °C for as-printed PLA to ≥ 150 °C, enabling deformation-free autoclave sterilization. Bioactive coatings with thicknesses of 20–50 μm remained stable after sterilization, especially for samples annealed at 180 °C. EDS analysis confirmed deep HA particle diffusion into the polymer matrix. Coating adhesion strengths between 83 and 139 MPa exceeded values commonly reported for polymer–ceramic systems and resisted bending stresses up to 91 MPa. These results demonstrate that powder bed annealing is a single-step, scalable process capable of integrating mechanical reinforcement, thermal stabilization, and osseointegrative surface formation, offering a practical manufacturing route for customized, sterilization-resistant PLA implants.