Preparation and properties of K_0.48Na_0.52NbO₃ ceramics for bone scaffolds via digital light processing

Lead-free piezoelectric ceramics are expected to be used for artificial bone scaffolds since they can generate electrical signals and promote recovery, but it is still difficult to fabricate piezoelectric scaffolds with complex structures. In this work, digital light processing (DLP) technology was used to fabricate potassium sodium niobate (K0.48Na0.52NbO3, KNN) bone scaffolds with gyroid triply periodic minimal surface. Suspension was first optimized to ensure both high solid loading (42 vol%) and high cure depth (>50 mu m). KNN porous scaffolds (porosity: 60%) and other samples for tests were printed successfully. Then, influences of sintering temperature on microstructure, relative density and mechanical properties were discussed. Results showed that when sintered at 1090 degrees C, printed KNN ceramics had the highest relative density (90.11%) and lowest open porosity (5.75%), and exhibited the most satisfying mechanical properties (compressive strength: 33.85 MPa, elastic modulus: 1.87 GPa, flexural strength: 35.40 MPa, hardness: 2.39 GPa), which can meet the requirements of cancellous bone. Finally, the electric properties of samples at room temperature were verified. With d(33) being 113.67 +/- 2.49 pC/N and P-r being 19.94 mu C/cm(2), printed KNN ceramics showed comparable piezoelectric and ferroelectric performances with traditionally dry-pressed samples. These results indicated that DLP technology is competitive in preparing KNN piezoelectric bone scaffolds for implantation.