Invited: 3D Printing: From the “Ink” to the Medical Device

Introduction: Contrary to the vast majority of the 3D constructs printed to date, which are static in nature, our work aims at engineering dynamic architectures that change “on command” or over time. This contribution focuses on the development of a series of environmentally responsive 3D printable polymers and the generation of 3D printed constructs responsive to temperature, pH or a magnetic field.

Methods: 3D printable polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-PPO-PEO) triblocks and acrylic acid were co-printed and are responsible for the reverse thermo-responsive and pH sensitive behavior of the 3D printed structures.

Results: The water absorption behaviour and dimensional changes exhibited by the different environmentally responsive 3D printed constructs, markedly responded to temperature and pH changes. Our findings revealed that the 3D printed structures absorbed more water when below the thermal transition and also when at a pH above acrylic acid’s pK_a value. All the printed structures showed a fast and reversible swelling-deswelling response, as they fluctuated between pH 2.0 and pH 7.4 and between 6°C and 37°C. Additionally, by adding magnetic nanoparticles (MNP) to the “ink” being printed, shape memory displaying structures able to be remotely actuated by an alternate magnetic field were engineered. By controlling the MNP content, temperatures between 47°C and 75°C were achieved, allowing the shape memory response of different polymers.

Conclusion: The distinctive spatial resolution of 3D printing technologies was successfully harnessed to produce environmentally responsive biomedical structures, with unique properties.