Engineers at Cornell University used 3D printing techniques to build a new external human ear. The outer ear, also called the auricle, or pinna, was constructed using an extrudable gel made of living cells. Over a 3 month period the ears grew cartilage to replace the collagen base that was used to mold them. Cartilage is an ideal tissue for 3D printed biostructures since it can persist in the absence of vascularization. Formerly, artificial replacement ears had been built from a more styrofoam-like material or sometimes from pieces harvested from a patients rib — a difficult and typically painful procedure, particularly for children.
The pinna is much more than just an ornamental curiosity. Without it, sound localization in the median plane is severely compromised. This is because the pinna, together with the ear canal form a selective filter which imparts direction-selective resonances onto the frequency response of the ear. Specific resonances induced by the pinna may also aid in determining the distance of the sound source.