Cancerous tumors, infections or bad fractures can make it necessary to surgically remove bones and insert implants in their place. In collaboration with European partners, Fraunhofer researchers have now developed a technique with which bone implants that are precisely fitting, stable and variable in dimensions can be 3-D printed from a special plastic. The secret lies in the printing process, where the individual layers are treated with a cold plasma in order to improve the bonding of bone-forming cells.