The self-charging air filter (IMAGE) City University of Hong Kong Caption The self-charging air filter (SAF) developed by Dr Yang Zhengbao and his team at City University of Hong Kong. Credit © Dr Yang Zhengbao’s Group / City University of Hong Kong Usage Restrictions Image must be used with appropriate caption and credit. 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.