Flexible 3D-Printable Materials for Application in Medical Research: A Comprehensive Comparison of Commercially Available Materials

Additive manufacturing has become an important tool in modern medicine with numerous applications such as therapy planning, medical device prototyping and testing, and basic research. While the range of available materials continues to grow, the field of elastic printable materials for medical applications has not been fully explored. Therefore, this study focuses on the comparison of six commercially available flexible printing materials regarding their usability in the medical field. Surface of printed parts for all materials were analyzed directly after printing by scanning electron microscopy. The mechanical behavior was evaluated by uniaxial tensile tests, shore A hardness, and vascular compliance analysis. The degradation effects of the solvents water, glycerin, and ethanol were analyzed over a period of 7 days. The impact of different sterilization protocols (steam, plasma, ethylene oxide) was determined by tensile testing and surface imaging. Cytotoxicity was evaluated by a WST-1 proliferation assay with human endothelial cells. Microscopic imaging revealed a uniform surface with characteristic topologies depending on the printing technique. Different sterilization techniques revealed good results, however, pure silicone material TrueSil^® showed complete mechanical failure after plasma sterilization. All materials demonstrated high resistance to water and glycerin exposure with only slight weight changes. Ethanol exposure led to significant increases in wet weight with Agilus30 reaching a weight increase of 104.6%. All materials except Aceo showed a decrease in dry weight after ethanol exposure. Formlabs' Flexible 80A and Elastic 50A, as well as Agilus30, showed high cytotoxicity with no cell viability after 24 h. Aceo and TrueSil silicone materials revealed adequate cytocompatibility with viable cells even after 7 days. Static and dynamic vascular elasticity of all tested materials revealed linear elastic behavior. The tested materials offer unique material properties for different use cases, with the recapitulation of vascular elasticity still being a weak point of current printing technologies.