3D Printing of Resorbable Metal-Photopolymer Composites Via Novel Vat Agitation System

Abstract

While metallic resorbable materials offer excellent mechanical strength, they are challenging to additively manufacture. In contrast, polymer-based resorbable materials are generally well suited for additively manufacturing but often lack the mechanical properties required for structural implant applications. Incorporating metallic powder additives into polymer feedstocks has improved the mechanical properties of several additively manufactured materials. However, this approach has not been extensively explored for the development of resorbable metal-polymer composites, especially within vat-based additive manufacturing. One potential barrier to the application of reinforcing metallic particles in these fields is the problem of particle settling during vat-photopolymerization additive manufacturing, which can produce non-uniform material compositions and print defects. This study presents both a novel suspension-maintenance methodology for vat-photopolymerization, achieved through continuous mixing of the feedstock during the printing process, and a new additively manufacturable and resorbable composite resin designed to combine the advantages of metallic and polymeric materials without compromising resorbability or biocompatibility. The composite resin was formulated using poly(ethylene glycol) diacrylate (Mn = 250) activated with diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide and reinforced with microscale magnesium particles at concentrations ranging from 0.0 to 6.0 wt%. The agitated resins were fabricated using masked-stereolithography and evaluated for printability through visual assessment and dimensional accuracy measurements to determine the effects and practical limits of both magnesium incorporation and the use of continuous mixing during printing. Composite specimens of each composition were subsequently characterized through compressive and tensile mechanical testing, microscopy, and mass-loss dissolution studies to evaluate the influence of magnesium addition on mechanical properties and degradation behavior, while also assessing the particle distributions within printed parts. Compression testing to failure was performed using cylindrical specimens measuring 15 mm in diameter and 40 mm in height, while tensile testing to failure was conducted using ASTM type V polymer specimens. The findings demonstrate the feasibility of maintaining homogeneous particle suspensions during vat-photopolymerization without modifying the resin formulation and establish a foundation for future optimization of mechanically enhanced resorbable composites for additive manufacturing.