Space Key in door (IMAGE) Aalto University Caption Copper is a material that stays clean germ-wise, as it is naturally toxic to microbes without the need for processing or charging. Even patina on the surface does not reduce its effectiveness. Credit Erwin Laiho Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.