Transfer of a rational formulation and process development approach for 2D inks for pharmaceutical 2D and 3D printing

The field of pharmaceutical 3D printing is growing over the past year, with Spitam® as the first 3D printed dosage form on the market. Showing the suitability of a binder jetting process for dosage forms. Although the development of inks for pharmaceutical field is more trail and error based, focusing on the Z-number as key parameter to judge the printability of an ink. To generate a more knowledgeable based ink development an approach from electronics printing was transferred to the field of pharmaceutical binder jetting.

Therefore, a dimensionless space was used to investigate the limits of printability for the used Spectra S Class SL-128 piezo print head using solvent based inks. The jettability of inks could now be judged based on the capillary and weber number. Addition of different polymers into the ink narrowed the printable space and showed, that the ink development purely based on Z-numbers is not suitable to predict printability.

Two possible ink candidates were developed based on the droplet momentum which showed huge differences in process stability, indicating that the used polymer type and concentration has a high influence on printability and process stability. Based on the study a more knowledgeable based ink design for the field of pharmaceutical binder jetting is proposed, to shift the ink design to a more knowledgeable based and process-oriented approach.

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Materials

For the investigation of the jettable windows, different solvents were used: tri(ethylene glycol) monoethyl ether (TGME, Sigma-Aldrich, USA), isopropanol (technical grade, Th. Geyer, Germany), an aqueous 1% (w/w) polysorbate 20 solution (Tween 20, Caesar & Loretz, Germany), and different glycerol solutions prepared from glycerol 85% (Ceasar & Loretz, Germany). The binder containing inks consisted of different aqueous solutions of either polyvinylpyrrolidone K25 (PVP K25, BASF, Germany), polyvinyl alcohol 4–88 (PVA Parteck® MXP, Merck, Germany) or polyvinyl alcohol 18–88 (PVA, Emprove® Essential, Merck, Germany) and 1% w/w Tween 20 for surface tension adjustment.

Maximilian Schulz, Malte Bogdahn, Simon Geissler, Julian Quodbach, Transfer of a rational formulation and process development approach for 2D inks for pharmaceutical 2D and 3D printing, International Journal of Pharmaceutics: X, 2024, 100256, ISSN 2590-1567, https://doi.org/10.1016/j.ijpx.2024.100256.

Read also our introduction article on Binders here: