A complete 3D-printed multiscale tracheobronchial tree for aerosol deposition assessment.

The complex and multiscale structure of the lung's airways is extremely difficult to mimic experimentally using in vitro models. Here, we 3D-printed using additive manufacturing a model at human scale of the complete tracheobronchial airways from mouth down to the 14th airway generation. By adding a "bending" angle between parent airways and the plane of the daughter airways we successfully created 16 tightly packed airway clusters each spanning generations 4 to 14. This strategy eliminated the need for using support material within the airways, greatly simplifying the printing process. In a proof-of-concept, we demonstrate the usefulness of our multiscale airway model in predicting regional aerosol deposition for inhalation therapy by measuring the deposition of salt-laden aerosol droplets from commercial inhalers within the different model regions. We compare our results to those from a well-established in silico 1D-model. Our in vitro lungs encompass for the first time the multi-scalar features of the conducting airways without truncation and represent a tangible step towards a wider vision of reconstructing in vitro the full lung anatomy for pulmonary drug delivery endpoints.