3D Printing of Poly(propylene fumarate) Oligomers: Evaluation of Resin Viscosity, Printing Characteristics and Mechanical Properties

Abstract

Complex three-dimensional (3D) pore geometries, useful for tissue engineering scaffolds, can be fabricated via photo-crosslinking of resorbable poly(propylene fumarate) (PPF) resins using stereolithography (SLA) and/or continuous digital light processing (cDLP) methods. Physico-chemical parameters inherent to 3D printable resin design, include viscosity, polymer concentration, degree of polymerization, and resin printing temperature. We report here on our study of these parameters and their influence the cDLP 3D printing process and the resulting mechanical properties. A series of PPF oligomers were synthesized by the ring-opening copolymerization (ROCOP) of maleic anhydride and propylene oxide followed by a base-catalyzed isomerization. The resin viscosities were measured as a function of number-average molecular mass ( M n ) of the PPF oligomers (1.1, 1.7 and 2.0 kDa), concentrations of PPF in the reactive diluent diethyl fumarate (DEF) (50 and 75 wt %) and resin temperature (25 to 55 °C). The zero-shear viscosity (η 0 ) of the resins was found to be temperature-dependent and follow a linear Arrhenius relationship. Tensile tests demonstrated mechanical properties within the range of trabecular bone, with the ultimate strength at break above 15 MPa and elastic moduli between 178 and 199 MPa.

Three-dimensional Printing of Customized Bioresorbable Airway Stents

“…However, the viscosity of the copolymers with longer chain length (MW > 5000 g mol -1 ) was still above the range required for DLP printing ( Supplementary Fig. 3) 21 . To tackle this issue, we designed a customized temperature-controlled printing platform that allows for a reduction of the polymer viscosity by heating the resin tray ( Supplementary Fig.…”

“…This specific manufacturing technology is based on the localized light-initiated photopolymerization of a liquid resin containing (macro)monomers 6,20 . While DLP offers the benefit of very high resolution compared to other 3D printing techniques, it also heavily depends on the resin viscosity 21,22 . Low-viscosity biodegradable and biocompatible biomedical resins are currently…”

Two‐Step Solvent‐Free Synthesis of Poly(hydroxybutyrate)‐Based Photocurable Resin with Potential Application in Stereolithography

“…As reviewed by Chartrain and co‐workers, [ 4 ] such high resolution is a crucial aspect in the manufacturing of custom‐made scaffolds for tissue engineering, making SLA an innovative fabrication approach in medical fields as dentistry, maxillofacial surgery, and orthopedic reconstruction. Typically, a suitable resin for SLA consists of methacrylate or acrylate terminated low molecular weight (MW) polymer or oligomers mixed with a suitable high boiling reactive [ 5 ] or non‐reactive [ 6 ] diluent, which is required for dealing with highly viscous, [ 7 ] or even solid macromonomers. [ 8 ] Indeed, both suitable viscosity (lower than 5 Pa s) [ 2 ] and presence of photo‐sensible terminals are key factors to have a tailored and localized 2D solidification through a photo‐induced cross‐linking process.…”

Engineered 3D Polymer and Hydrogel Microenvironments for Cell Culture Applications

“…Structure, Feature Size, and Porosity PPF mixed with the DEF/TCP and photoinitiator BaPO have been used to fabricate scaffolds via micro-stereolithography (µ-SLA), with pore sizes down to 150 µm and porosity up to~80% [124]. Because PPF is highly viscous, dilution in a solvent such as DEF is necessary for control over feature size [125]. Besides substrates for tissue engineering and cell culturing, microneedles with a tip radius of~50 µm for drug delivery have been fabricated using PPF and µ-SLA [126].…”

“…PPF degrades in the body into a Krebs cycle constituent (fumaric acid) and a food additive (propylene glycol). In addition, the degradation properties of PPF structures can be tuned by the use of ring-opening copolymerization methods to synthesize PPF with specific molecular masses; the integration of diluents such as DEF to change its viscosity; and the tuning of photoinitiators' concentration to affect the polymerization kinetics [125,133].…”