Comparative investigations on key factors and print head designs for pharmaceutical inkjet printing

The interest in using inkjet printing as manufacturing technology for personalized medicine has increased in recent years. The print head is the centrepiece of an inkjet printer. For pharmaceutical approaches, various types of printing equipment were tested in the past, but comparative investigations in relation to pharmaceutical use are still lacking. In the present study, two piezoelectric print heads of different designs (Spectra SE-128 AA and Konica Minolta KM512SHX) were systematically compared with the objective of deepening the process understanding and identifying the key factors on the resulted quantities. As substrates, oral thin films made from 15% (w/w) hypromellose (HPMC) casting solution were used. The Spectra print head with bigger nozzles was more efficient in one pass and resulted in less scattering (RSD <= 5%). Furthermore, it was found that liquid excipients like polyethylene glycol 400 characterized by low vapour pressure and limited penetration into the HPMC based films are not suitable. The choice of the printed geometry plays a subordinate role when printing the same surface area, whereas the composition of the inks, set process parameters as well as the size and functionality of the nozzles have a significant impact on the final printed quantity.