Masked Stereolithography of a Metacarpal Fixation Plate Prototype with a Low-Temperature Barium Titanate Coating

Fifth metacarpal shaft fractures account for a large share of hand trauma and often require operative internal fixation, yet conventional dorsal plates and cannulated screws present a stiffness mismatch with native bone and the insertion of screws can shear surface coatings. This study presents the design, fabrication, and preliminary characterisation of a low-profile, BaTiO3-coated dorsal fixation plate prototype for the fifth metacarpal bone. A curved, 0.5 mm plate was modelled in SolidWorks and overlaid with a randomised Delaunay lattice in Meshmixer, achieving 73.6% porosity with a 70% mesh reduction strategy. A linear static finite element study of a simplified periodic surrogate of the plate (nominal polymer properties, 300 N load) is reported only as an illustrative response, not as evidence of mechanical suitability. Plates were manufactured by masked stereolithography in a water-washable resin not intended for implantation (not MED610), with an average accuracy of 98.77% on three features measured before coating; the dimensions after the 120 °C and 180 °C coating steps were not remeasured. A barium titanate precursor was synthesised via the propionate route and deposited through a three-cycle, low-temperature (120 °C) submersion process followed by a solvothermal treatment at 180 °C for 1 h. Optical microscopy and SEM/EDS showed qualitative surface coverage with barium and titanium and open pores, and XRD showed reflections consistent with perovskite BaTiO3; the polymorph, thickness, adhesion, uniformity and mechanical stability of the coating were not quantified. Under cyclic compressive loading (1–2 N), a coated plate dried at 120 °C, before the solvothermal step was introduced, generated an alternating open-circuit voltage of 0.62 ± 0.08 V at 1 N and 0.93 ± 0.10 V at 2 N (peak-to-peak), much larger than that of an uncoated plate; its origin remains to be established. This is a fabrication and preliminary characterisation study of a non-biocompatible prototype: mechanical testing of the printed structure, poled and replicate electrical measurements, and biological evaluation have not yet been performed and are the next steps.