On polypropylene-samarium doped ZnO-based composites for the 3D printing of sensor-integrated implants

Abstract

Over the last two decades, extensive studies have been reported on polypropylene (PP) and its composites for biomedical applications. But hitherto little has been reported on PP reinforcement with samarium (Sm)-doped zinc oxide (ZnO) for the manufacturing of sensor-integrated implants. In this study, the PP matrix was reinforced with various proportions of Sm-doped ZnO and characterized to identify a suitable composite for the fabrication of a sensor-based implant. The four compositions of samples were prepared (sample-1: virgin PP, sample-2: PP-1% Sm-(1% doped)-ZnO, Sample-3: PP-1% Sm-(2% doped)-ZnO, sample-4: PP-1% Sm-(3% doped)-ZnO) with a slight variation of ZnO doping percentage in Sm. The melt flow index (MFI) was ascertained per ASTM D1238 for the prepared composite, and it was observed that sample 4 had the highest (13.9 g/10 min) MFI, while sample 1 had the lowest (12.22 g/10 min) MFI. After the MFI, the prepared PP composite was tested for mechanical properties. The result suggested that the maximum Young’s modulus (E) of 302.31 MPa was observed in sample-4, and the minimum E was observed in sample-1 (59.86 MPa). The thermogravimetric analysis (TGA) of sample 4 yielded the highest residue (2.24%). In contrast, sample 1 had the lowest (-2.88%) residue. Also, in differential scanning calorimetry (DSC), sample 4 shows the lowest heat loss (11.92 J/g) among the other samples, suggesting a thermally stable composite suitable for a sensor-integrated implant. Fourier transform infrared (FTIR) spectroscopy revealed strengthening, with new peaks observed in sample 4 at 3283 cm⁻¹ (O-H interfacial) and 1595 cm⁻¹ (COO^–/Sm-O) along the PP bands. A significant improvement in E was observed in sample 4, indicating the optimal composition for the sensor-based implants. Further, the minimum voltage-resistance (V-R) of 88.84 Ω in sample 4 enables low-power e-sensing and Shore-D of 43.6 HD, matched tissue compliance, and reduced stress shielding. The results are supported by scanning electron microscope (SEM) based morphological analysis.