Effect of Infill on Resulting Mechanical Properties of Additive Manufactured Bioresorbable Polymers for Medical Devices

Abstract

The crossover between additive manufacturing (AM) and bioresorbable materials play a critical role in development of a new bioresorbable medical devices. When combined with the innovation and technological advances of additive manufacturing, the use of bioresorbable polymers could prove tremendous to the development of custom bioresorbable implants. However, a key question for the use of thermoplastic based resorbable polymers lies in the potential changes in properties experienced during manufacturing, and thus the effect of process parameters on the performance of the final device is of critical importance. Specific resorbable materials are selected for mechanical and resorption rate properties based on bulk measurements. The implanted mechanical properties of a device are significantly affected by processing parameters and are the leading concern of clinicians during development and patient use of a new device. In this work, additive manufacturing of medical grade polymers and copolymers of L-lactide, ε-caprolactone were extruded into filaments of 1.75 mm in diameter and printed at different infill percentages. The molecular, thermal, and mechanical properties of homopolymers of L-lactide and ε-caprolactone, along with a unique copolymer of L-lactide, ε-caprolactone, and trimethylene carbonate, Lactoflex® 7415 were evaluated. Through variance of material composition and the infill parameter of AM, an order of magnitude range in tensile strength and modulus properties were observed as feasible and optimizable.

Keywords: bioresorbable polymer, additive manufacturing, mechanical properties, infill, polylactide, polycaprolactone