In the search of materials valid for direct ink writing (DIW) 3D printing and with special interest for the biomedical and
pharmaceutical applications, the development of bioactive inks for DIW is of great interest. For that purpose, in this work
bioactive waterborne polyurethane–urea inks were prepared by addition of natural extracts (logwood, chestnut, and alder
buckthorn) and cellulose nanofibers (CNF). The rheological behavior of the inks proved to be strongly dependent on the
extract type and content, and the addition route used. Inks prepared by ex-situ incorporation of the extracts showed a strong
gel-like behavior, as did inks prepared with chestnut and alder buckthorn extracts, which, in turn, hindered a continuous
flow during the printing process, resulting in 3D printed parts with poor shape fidelity. On the other hand, inks prepared insitu
and with logwood extract showed more facility to flow and higher homogeneity, which translated in better printability
and better shape fidelity, further enhanced for CNF containing inks. 3D printed composites showed reinforced mechanical
behavior, as well as in materials with enhanced antibacterial behavior. Overall, the possibility to successfully prepare bioactive
inks valid for 3D printing was proven.
